MEETING OF THE ADVISORY 

COMMITTEE ON IMMUNIZATION 

PRACTICES (ACIP)

SEPTEMBER 22-23, 2021 

SUMMARY MINUTES 

Table of Contents

Meeting Purpose........................................................................................................................ 3

Wednesday: September 22, 2021.............................................................................................. 3

WELCOME AND INTRODUCTIONS ...................................................................................... 3

CORONAVIRUS DISEASE 2019 (COVID-19) VACCINES ..................................................... 4

Introduction......................................................................................................................... 4

Safety and Immunogenicity for a Third Dose of BNT162b2................................................. 5

Adaptive Immunity and SARS-CoV-2.................................................................................13

Vaccine Effectiveness Studies in the United States ...........................................................19

Modeling the Potential Impact of Booster Doses in Nursing Home Residents ....................25

Vaccine Safety Technical Work Group (VaST WG) Assessment of 3rd Dose Safety Data..33

COVID-19 Work Group Summary ......................................................................................35

Pregnancy: Safety Monitoring in v-safeSM ..........................................................................41

Pregnancy: Safety Monitoring in the Vaccine Safety Data Link (VSD)................................45

VaST WG Summary on Pregnancy....................................................................................47

Updates on COVID-19 and Pregnancy ..............................................................................48

Summary of Discussion .....................................................................................................51

Thursday: September 23, 2021................................................................................................53

WELCOME, ROLL CALL, OPENING REMARKS BY DRS. FINK AND WALENSKY .............53

CORONAVIRUS DISEASE 2019 (COVID-19) VACCINES ....................................................55

Introduction........................................................................................................................55

Public Comments...............................................................................................................55

COVID-19 Vaccine Booster Doses: Benefit-Risk Discussion..............................................63

EtR Framework: Booster Doses of Pfizer-BioNTech COVID-19 Vaccine ...........................66

Interim Clinical Considerations for Pfizer-BioNTech COVID-19 Vaccine Booster Doses ....74

Types of Recommendation ACIP Could Make ...................................................................76

Motion/Vote #1...................................................................................................................87

Motion/Vote #2...................................................................................................................87

Motion/Vote #3...................................................................................................................88
ACIP Meeting Summary September 22-23, 2021

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Motion/Vote #4...................................................................................................................88

CLOSING REMARKS AND ADJOURNMENT........................................................................93

Certification...............................................................................................................................94

ACIP Membership Roster .........................................................................................................95

Acronyms Used in the Document............................................................................................104
ACIP Meeting Summary September 22-23, 2021

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Meeting Purpose

The United States (US) Department of Health and Human Services (HHS) and the Centers for 

Disease Control and Prevention (CDC) convened an emergency meeting of the Advisory 

Committee on Immunization Practices (ACIP) on September 22-23, 2021. The meeting took 

place remotely via Zoom and teleconference. This document provides a summary of the 

meeting, which focused on the topic of a third dose of the Pfizer/BioNTech BNT162b2 SARSCoV-2 vaccine.

Wednesday: September 22, 2021

 

Welcome and Introductions

Dr. Grace Lee (ACIP Chair) called to order and presided over the first day of the 12th ACIP 

meeting convened in 2021. 

Dr. Amanda Cohn (ACIP Executive Secretary, CDC) welcomed everyone and introduced new 

ACIP member, Dr. Jamie Loehr, from Cayuga Family Medicine in Ithaca, New York. She noted 

that while the current agenda was for a 2-day meeting, the agenda for the second day remained 

to be determined and would be finalized if the Food and Drug Administration (FDA) authorized a 

third dose of the Pfizer product before the opening time scheduled for the second day. She 

explained that there would be an oral public comment session at approximately 12:20 PM 

Eastern Time (ET) on September 23, 2021. Given that many more individuals registered to 

make oral public comments than could be accommodated, selection was made randomly via a 

lottery. Those individuals who were not selected and any other individuals wishing to make 

written public comments were encouraged to submit them through https://www.regulations.gov

using Docket Number CDC-2021-0104. Further information on the written public comment 

process can be found on the ACIP website.

Dr. Cohn reminded everyone that ACIP members agree to forgo participation in certain activities 

related to vaccines during their tenure on the committee. For certain other interests that 

potentially enhance a member’s expertise, CDC has issued limited conflict of interest (COI)

waivers. Members who conduct vaccine clinical trials or serve on data safety monitoring boards 

(DSMBs) may present to the committee on matters related to those vaccines, but are prohibited 

from participating in committee votes. Regarding other vaccines of the concerned company, a 

member may participate in discussions with the provision that he/she abstains on all votes 

related to that company. At the beginning of each meeting, ACIP members state any COIs. 

Dr. Lee (ACIP Chair) briefly highlighted a few key points about the ACIP’s process for 

recommendations, sharing a figure depicting the vaccine life cycle. She explained that to move 

from science and Data to recommendations, vaccine manufacturers typically submit clinical trial 

data to the FDA in their application for licensure or authorization in this instance. The FDA 

conducts a rigorous and independent review of the data that are submitted to the FDA as part of 

that application. The previous week, the FDA convened its Vaccine and Related Blood Products

Advisory Committee (VRBPAC) to provide advice to the Commissioner of the FDA on the issue 

of the booster dose application from Pfizer. The FDA then makes a determination on whether to 

approve a new vaccine or new indication for use of an existing vaccine. After the FDA’s 

regulatory decision, the ACIP typically has the period of time to review the data, GRADE 

(Grading of Recommendation Assessment, Development and Evaluation ) the scientific 
ACIP Meeting Summary September 22-23, 2021

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evidence, and deliberate on the Evidence to Recommendations (EtR) Framework for the policy 

question at hand. The ACIP then proceeds with a vote and recommendations for use of the 

vaccine in the US civilian population. As everyone knows, that cycle has gotten compressed to 

a very short timeline during the time of COVID.

In addition, Dr. Lee highlighted two key points in the ACIP Charter: 1) the role of the ACIP, 

which also is a federal advisory committee, is to provide advice and guidance to the Director of 

the CDC regarding use of vaccines in the civilian population in the US; and 2) recommendations 

made by the ACIP are reviewed by the CDC Director and, if adopted, are published. She 

emphasized that the ACIP’s process for deliberation would be continued throughout the day and 

thanked the ACIP Members, Ex Officios, and Liaison Representatives for their continued service 

to the committee. In addition, she thanked the entire CDC team for all of their contributions and 

for continuing to work around the clock to bring together all of the evidence and data needed to 

help support a robust decision-making process.

Dr. Lee then conducted the roll call. A list of Members, Ex Officios, and Liaison Representatives 

is included in the appendixes at the end of this summary document. No COIs were declared by

any voting members.

Coronavirus Disease 2019 (COVID-19) Vaccines

Introduction

Dr. Matthew Daley (Chair, ACIP COVID Vaccines WG) introduced the Coronavirus Disease 

2019 (COVID-19) Vaccines session for the first day of the meeting. He reported that in terms of 

daily trends in the number of COVID-19 cases in the US,1there were more than a 150,000 new 

cases between January 23, 2020 and September 17, 2021. Over the course of the pandemic, 

there have been almost 42 million cases in the US. At the most recent date, there were 2087 

COVID-19 deaths in the US.2 This translates to nearly 100 individuals every hour who are dying 

from COVID-19 in the US. In September 2021 in the US, death from COVID-19 is largely 

vaccine-preventable with the primary series of any of the three vaccines available in the US.

During August and September of 2021, the COVID-19 Vaccine WG’s efforts have focused on

review and consideration of booster doses for COVID-19 vaccines in terms of the following topic 

areas:

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Real-world vaccine effectiveness (VE) studies in the US and abroad

RCT safety and immunogenicity of booster doses

Modeling of the impact of booster doses on COVID-19 in nursing homes

National Institutes of Health (NIH) booster data

Outbreaks among vaccinated people in congregate settings

GRADE of booster evidence

Benefit/Risk Analysis of COVID-19 vaccine booster doses 

EtR in terms of implementation, values, acceptability, resource use, and equity

1 https://COVID.cdc.gov/COVID-data-tracker/#trends_dailycases

2 https://COVID.cdc.gov/COVID-data-tracker/#trends_dailydeaths (accessed September 19, 2021)
ACIP Meeting Summary September 22-23, 2021

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Dr. Daley indicated that during the September 22, 2021 COVID-19 Vaccines session, there 

would be presentations on the following topics:

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Safety and immunogenicity of a third dose of BNT162b2 COVID-19 vaccine

Immunity and SARS-CoV-2

Vaccine effectiveness studies in the US

Modeling impact of booster doses in nursing home residents

Early safety monitoring for third doses

Vaccine Safety Technical (VaST) Work Group summary

COVID-19 WG summary 

Pregnancy: Safety monitoring in v-safeSM

Pregnancy: Safety monitoring in VSD 

Updates on COVID-19 and pregnancy

Safety and Immunogenicity for a Third Dose of BNT162b2 

Dr. Bill Gruber (Pfizer-BioNTech) began by presenting data of a booster or third dose of

BNT162b2 (COMIRNATY®) COVID-19 mRNA vaccine that support vaccine authorization and 

recommendations that Pfizer anticipates will maximize public health benefit. Data to support the 

need for a booster dose were presented in some detail the previous week to the VPBPAC. 

There is a briefing document and slides that speak to the details. The Kaiser Permanente 

Southern California (KPSC) work was accepted by Lancet and is in press. There are additional 

data in terms of post-hoc analysis, the randomized controlled trial (RCT) itself with the 

BNT162b2, and Israeli data that support the need, timing, and benefit of the booster dose.

In terms of an overview of the clinical program, the good news is that BNT162b2-elicited sera 

effectively neutralized a broad range of SARS-CoV-2 spike variants after 2 doses. Pfizer has yet 

to find a variant that escapes neutralization, including Alpha, Beta, Delta, and Lambda variants. 

Across the board, the neutralizing titers are well-maintained. Perhaps the lowest is for Beta, for 

which there are efficacy data from South Africa from Pfizer’s pivotal trial. As a reminder, there 

was a 0/9 split with 8 of the sequences determined to be South Africa and the 9

th expected to be 

as well. These data are very compelling and speak to the fact that if a third dose actually

generates sufficient antibody to the wild-type or vaccine virus, there is an expectation that it will 

restore protection against variants of concern now and into the future.3

Regarding how the third dose was evaluated in Phase 1 and Phase 3, participants from the 

original pivotal trial received 2 doses of vaccine administered 21 days apart. Pfizer took 

advantage of that population to further study the potential for a booster dose, first in Phase 1 

with 23 individuals and then in an expanded group to meet Phase 3 criteria. Reactogenicity and 

other safety events were captured when sampling was done at the 7 day and 1 month intervals.

Immunogenicity data from Phase 1 reveals useful information about the ability to boost 

response, the nature of maturation of that response, and shows how it bodes well for the 

potential for the vaccine to work effectively.

3 Data from Liu et al., 2021, Nature DOI: ; L10.1038/s41586-021-03693-y; Liu et al., 2021 NEJM, DOI: 10.1056/NEJMc2102017; 

Delta-AY.1, Lambda data submitted for publication
ACIP Meeting Summary September 22-23, 2021

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Post-dose 3 vaccine geometric mean titers (GMTs) provide a substantial boost and reduce the 

gap between wild-type and Beta variant neutralization. As expected after 2 doses, there is a 

robust immune response that is now known to be associated with 95% at efficacy in the months 

following vaccination. Especially gratifying is that despite the drop in younger adults and older 

adults, the drop in neutralizing activity just prior to the third dose was around 7 months after the 

2-dose series. There is a robust response of neutralizing antibody to both the wild0type and the 

Beta variant. The geometric mean ratio (GMR) after Dose 2 compared to after Dose 3 narrows,

suggesting a maturation of the response and that antibody continues to rise between 7 days

and 1 month, further suggesting broadening and maturation of the response that is likely to 

provide comparable protection to that seen after 2 doses and perhaps improved projection and 

greater durability of protection. It also was important to assess the Delta variant since this is the 

variant of greatest concern at this time. It also is gratifying the post-Dose 3 vaccine GMTs 

indicate a substantial boost to the Delta variant similar to wild-type. Once again, there is a very 

robust response to the booster among younger and older groups. Particularly in the older group, 

there is a narrowing of the ratio between the response to the wild-type and the Delta variant.

The safety profile after the third dose in the Phase 1 trial very closely mimics that seen after the 

second dose, so the combination of immune response and a satisfactory safety profile 

encouraged Pfizer to move to Phase 3. The subjects receiving the third dose were 

representative of 18 to 55 year olds in the parents study. There is good distribution in terms of 

gender, race, and ethnicity. Over 50% of the individuals had comorbidities by the Charlson 

Comorbidity Index, which includes risk factors as well as obesity and reflects risk factors seen in 

the original population that were noticed as part of the 1001 study. The mean age for booster 

vaccination was 41.3 years and the time from Dose 2 to the booster dose was close to 7 

months, with a range of between close to 5 months out to 8 months.

In terms of the immune response as seen in the Phase 3 trial that met criteria for approval, the 

GMR of neutralizing titers met the non-inferiority criterion specified by the FDA, with titers at 

least 3-fold higher than those seen after the second dose. The assay was a true neutralization 

essay in 210 individuals. The nature of the GMT responses one month post-booster dose 

versus one month after Dose 2 gives a ratio 3.29 and a lower confidence interval of 2.76, so this 

particular non-inferiority criterion was met. The other non-inferior criterion was a criterion of 

seroresponse. The non-inferiority of the booster dose was demonstrated based on the

proportion of subjects with a seroresponse. There was a 99.5% response one month postbooster dose and there was a 98% response one month after Dose 2, which is well within the

specified criteria that required a lower confidence interval greater than -10. This was -0.7, which 

is well above the criteria required to meet the FDA specification.

It was important to pair this up with safety information. Regarding the follow-up time for the 

expanded phase, the total exposure from booster vaccination to the cutoff date was 2.7 months 

with the median of 2.6 months. The total exposure from Dose 2 to the cutoff date, the entire time 

for which this population had been followed, is 9.4 months with a median of 9.5. Local reactions

were comparable between the third dose and the second dose. Particularly informative are the 

systemic events. Systemic events by maximum severity within 7 days of the third dose were 

similar to post-Dose 2 in the parent study. In addition to the reactions being similar, fever and 

chills were somewhat lower after Dose 3 compared to Dose 2. This suggests a lack of 

enhancement of reactions associated with the third dose and the fact that the safety profile may

be even somewhat better.
ACIP Meeting Summary September 22-23, 2021

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Unsolicited adverse events (AEs) and AEs by system organ class occurring at ≥1% one month

post-Dose 3 overall were less than those post-Dose 2 in the parent study, with the notable 

exception of blood and lymphatic disorders. The 5.2% is entirely represented by

lymphadenopathy, most of which was self-limiting. The investigator reported one individual to 

have severe lymphadenopathy by virtue of some limitation of arm movement, but this was selflimited and resolved by 4 to 5 days. The 0.6% by comparison post-Dose 2 is also largely 

represented by lymphadenopathy of 0.5%. Across the board, looking at lymphadenopathy and 

the nature of the other AEs, these are within an acceptable range for a good tolerability profile 

for a third dose. One individual had an acute myocardial infarction (MI). This was a 42-year-old 

who experienced an MI 62 days after Dose 3. This individual had a history of stimulant abuse 

and the investigator considered this unrelated to the vaccine and more likely related to the

stimulant abuse.

As part of the work Pfizer has done with approval, first under Emergency Use Authorization 

(EUA) and then full approval and licensure for the 2-dose series of vaccine in individuals 16 

years of age and above, there continues to be ongoing and active pharmacovigilance and 

pharmacoepidemiology. That has proven to be particularly useful in identifying rare AEs that are

not easily identified during the conduct of a clinical trial, notably events such as anaphylaxis and 

myocarditis. The rarity of the events associated with the benefit has supported a favorable riskbenefit profile for recommending the vaccine for 2 doses. Pfizer anticipates that this risk profile 

also will be seen after the third dose. This intensive pharmacovigilance and 

pharmacoepidemiology will continue to better define risk.

In summary, the safety and immunogenicity data meet the FDA criteria for the booster dose 

among those ≥16 years of age. The Phase 1 safety profile was satisfactory and notably, the 

Beta and Delta variants of concern responses after the third dose bode well for the ability to 

provide broad coverage against variants of concern now and in the future for both younger and 

older adults. The Phase 3 data revealed a safety profile similar or better than Dose 2. The 

elicited immune responses against the wild-type virus were non-inferior to responses observed 

post-Dose 2. The fact that they were statistically greater suggests the potential for not only 

providing protection equivalent to that seen with two doses of the vaccine, but also perhaps 

more sustained protections. The Phase 3 data met protocol pre-specified immunobridging

success criteria for GMTs and seroresponse rates. BNT162b2 is already demonstrated high 

efficacy after two doses. The types of immune responses seen and the real-world evidence

bode well for the vaccine to provide substantial benefit to those individuals who are boosted. 

Again, it is known that 2 doses of VE against severe disease and hospitalization remain high in 

most populations in the US, data from Israel predict that this may not be sustained. Pfizer is 

eager to maximize the potential for a booster dose to receive an authorization and a 

recommendation to provide the greatest public health benefit.

Discussion Points

Dr. Poehling expressed appreciation for the diversity of inclusion in the Phase 3 trial. 

Recognizing that COVID-19 has disparate impact across the nation, this is very important and 

there is an opportunity to continue to expand the diversity of the population. While Dr. Gruber 

shared the 1 month post-Dose 3 data, she asked what the plans are to follow the immune 

response in the future. In addition, she asked whether there were any episodes of myocarditis in 

these studies.
ACIP Meeting Summary September 22-23, 2021

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Dr. Gruber noted that Slide CC-5 represented Pfizer’s intentions in terms of follow-up. Active 

surveillance is ongoing, but that is expected to be challenged. It is expected that once a booster 

is recommended, the individuals who have not been boosted will need to be. Serum responses 

will be assessed at 6 and 18 months to get some measure of the persistence of antibody. In the 

Phase 1 data as shown, that tended to fall off very quickly. Pfizer is hopeful and expects that 

this may be more sustained. Antibody by itself may not be the basis of protection long-term and 

certainly memory is important. It was shown early on that cell-mediated immune (CMI) was 

particularly important in the absence of antibody. Ultimately, real-world evidence is going to 

provide the most useful information about maintaining protections. Pfizer, CDC, and others will 

be monitoring that closely. Given the rarity of myocarditis, no cases were experienced in the 

trial. It is in the label and Pfizer is very keen to ensure that they encourage individuals, 

investigators, and participants in the trial to be attentive to symptoms or signs that could be 

associated with myocarditis, so they provide specific guidance in all current protocols and will in 

those moving forward to alert individuals to report chest pain, palpitations, et cetera that might 

be associated with myocarditis. In addition, Pfizer routinely engages in pharmacovigilance after 

general use of the vaccine. While the Israeli data are limited, albeit it limited to not a full month 

for the full cohort who have now received a third dose, it was reassuring that there was only one 

episode of myocarditis in an individual over 30 years of age with a denominator of about 1.2 

million individuals. No myocarditis cases have been seen, with a fairly sizeable proportion of the 

Israeli population in the risk groups. That provides some comfort and is expected to be 

recapitulated with the US data once a large population is vaccinated.

Ms. Bahta asked what proportion of the people in the 18 to 55 years of age group were under 

24 years of age.

Dr. Gruber indicated that this information could be obtained and provided to ACIP before the 

vote the next day.

Dr. Daley asked what Dr. Gruber thought the relationship was between systemic reactogenicity 

and AEs such as myocarditis and whether anything could be inferred about myocarditis risk 

from the reactogenicity profile presented during this session. In addition, he requested clarity 

about whether there were individuals over the age of 55 who were in the Phase 1 study but 

none in Phase 3, so there was extrapolation to that group from the Phase 3 study findings.

Dr. Gruber observed that it would be useful information if myocarditis risk, as rare as it is, 

tracked in some way with increased reactogenicity. If that proves to be the case, it could be 

argued that less reactions would be seen after the third dose. CDC is better equipped to 

address this because they have a lot more information about how those two may track together, 

but it occurred to him that one reasonable hypothesis also might be that those people with 

myocarditis may not be getting a third dose and might drop out. That means that the individuals 

without risk will not show up. That will have to be part of the decision about recommendations.

In terms of individuals 55 years of age and older, the regulatory guidance from the FDA was that 

it would be possible to study a segment of the population 18 to 55 years of age and extrapolate 

that both from a safety and an immune response perspective to the group at large for which 

Pfizer was seeking an indication from 16 years of age and up. That guidance makes sense in 

terms of the nature of the reactions seen after the second dose among older compared to 

younger individuals, given that the older individuals had fewer reactions. Coupled with what was 

observed in Phase 1, which was similar, and the reduction observed after the third dose in 

reactions, particularly for fever in those 18 to 55 years of age, that provides compelling evidence 

that the reactions are likely to be less in the older age groups. Likewise for immune response, in 

addition to the Phase 1 data and although the sample was small, what was seen in the post-
ACIP Meeting Summary September 22-23, 2021

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Dose 3 individuals 18 to 55 years of age was predictive in that the responses after the third 

dose were robust. In Phase 1, the responses among 65 year olds rivaled those seen in the 18 to 

55 year olds, so there is every expectation that the same thing would be seen in older 

individuals. The real-world evidence from Israel is very compelling in that a high proportion of 

individuals vaccinated have been over 60 years of age have restored efficacy above 95%. In 

fact, the majority of individuals over 60 years of age in Israel have now been vaccinated with a 

third dose. This predicts reliably that those 65 to 85 years of age will have a robust protective 

immune response.

Dr. Sanchez requested clarification whether only groups 18 to 55 and 65 to 85 were included in

the studies assessing the third/booster dose and the 16 to 17 and 56 to 54 groups were 

extrapolations of the other data.

Dr. Gruber indicated that there were no 16 to 17 year olds in the booster study. The study that 

was submitted for EUA includes the Phase 1 data in those 65 to 85 years of age, but there are 

no additional data as part of that submission in the older age group. The regulatory guidance 

when the protocol was first proposed and then approved by the FDA suggested that was 

sufficient. The rationale that he shared with Dr. Daley supports that guidance.

Referring to slide CC-10, Dr. Kotton observed that about 57% had a co-morbidity of either 

hypertension, obesity, or meeting the Charleston Comorbidity Index (CCI). She asked how may 

of these were immunocompromised in the Phase 3 study. Immunocompromised persons 

comprise about 3% of the US population and she wondered whether that was represented in 

the cohort and whether anything further could be said about that population.

Dr. Gruber indicated that since these individuals were drawn from the 1001 study, individuals 

judged by the investigators to be immunocompromised were not included. They could have a 

past history of cancer or immunocompromising conditions, but if they were on chronic long-term 

steroids, were receiving other immunosuppressive agents, or the nature of their underlying 

disease was immunosuppressive, they were not included. Pfizer has reported out the number of 

individuals who had underlying cancer, with an abstract being presented and a manuscript that 

carved out that population after 2 doses. He did not know off hand how many were in the Phase 

3 cohort of 306. No one was immunocompromised to the extent that now, there is a label 

indication for individuals who are immunocompromised to receive a 3-dose primary series.

Ms. McNally asked Dr. Gruber to comment on whether Pfizer is conducting trials or plans trials 

to evaluate the safety and immunogenicity of the Pfizer booster vaccine after the completion of 

a primary series with either Moderna or J & J vaccine.

Dr. Gruber indicated that Pfizer is not sponsoring trials but welcomes the trials that are being 

conducted by the National Institutes of Health (NIH) in the US and trial abroad, particularly in the 

United Kingdom (UK) that are assessing combinations of mRNA vaccines either as priming 

doses or as a booster dose and vice versa with adenovirus vector vaccines and their 

competitor’s mRNA vaccine. That information will be useful in informing public health policy. 

Pfizer’s focus has been on providing as much information as possible about the series of 

immunizations that they think best provides protection.
ACIP Meeting Summary September 22-23, 2021

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Dr. Beigel (NIH) added that the National Institute of Allergy and Infectious Diseases (NIAID) is 

currently conducting a study evaluating all 3 EUA vaccines as boosters. This is essentially a 3 x 

3 study in which people present who have received a primary series with Moderna, Janssen, or 

Pfizer and are then boosted with Moderna, Janssen, or Pfizer. That study is ongoing and while 

data are not available to present yet, they hopefully will be available very soon.

Dr. Brooks asked whether there were any variances by race or ethnicity in response and, if so, 

whether they were statistically significant.

Dr. Gruber said that based on what they saw with the second dose of vaccination and the more 

exuberant responses seen after the third dose, there was evidence across racial and ethnic 

groups that were essentially indistinguishable in terms of efficacy with a much larger database 

with over 40,000. Given the response observed after the third dose, there is an expectation that 

the responses are likely to be adequate. 

Dr. Czech indicated that they have not yet done subgroup analyses. Regarding an earlier 

question, about 6.5% of the subjects were 18 to 25 years of age in this population.

Dr. Duchin (NACCHO) asked whether an alternate interval for the primary would enhance the 

duration and perhaps degree of protection, and whether that would have implications in the 

future when transmission is lower to have a better response with the primary series.

Dr. Gruber indicated that Pfizer is exploring a number of potential options about how to optimize 

protection. One of the challenges faced from the beginning that was considered to be an 

advantage regarded how to protect people as quickly as possible in the midst of the pandemic. 

After seeing the Phase 1 data following 2 doses, that led them to select the 21-day interval as 

opposed to waiting even longer to provide protection. As it turns out, there was high protection 

12 days after the first dose. Others in Europe have looked at this and Pfizer welcomes that 

information and will continue to explore whether it makes sense to consider a longer interval. 

That makes particular sense once out of the pandemic situation. Obviously, they do not want to 

compromise people between the first and second dose and leave people uncovered.

Dr. Kimberlin (AAP Redbook) pointed out that if there was a correlate of protection, a lot of the 

considerations about booster doses would be simpler. He asked what Pfizer is doing to identify 

a correlate of protection in those who have breakthrough infections versus those who do not 

and when those answers will be available.

Dr. Gruber said that to some extent in terms of the basis for comparisons being made, a 

reasonable assumption has been made that antibody response comparison can be a basis for 

approval. In this case, GMTs and seroresponses are being compared. The nature of correlates 

is tricky because antibody drops off fairly quickly and faster than the efficacy seen for overall 

COVID-19 and particularly for serious infection. There is more to this than antibody, so it is not 

so simple to rely on antibody response. It is a useful marker to make the types of comparisons 

that are being done to meet regulatory criteria. Pfizer is interested ultimately in looking at how 

this can be considered as a correlate of protection. They will know more about this after the 

booster dose and observation of what happens with durability in relationship to antibody in 

terms of real-world evidence—likely into next year.
ACIP Meeting Summary September 22-23, 2021

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Dr. Loehr recalled that during the last ACIP meeting, Dr. Stanley Plotkin broached the idea that 

these should not be called “booster doses” and instead should be considered to be part of the 

primary series and raising the antibody levels as is done with other vaccines that have a 6-

month series process. He asked Dr. Gruber to comment on whether he though that was a 

reasonable concept.

Dr. Gruber said it was a reasonable hypothesis based on what is known about other vaccines 

that either require significant spacing between a first and second dose or a 3-dose series in 

which the third dose is spaced after the second. He has heard two contending positions, one of 

which is that this could well be a circumstance where after a third dose protection is maintained 

and perhaps enhanced over a longer period of time. He likes that and thinks that if that proves 

to be the case, they may come to a realization post-hoc that this is really 3 doses, after which 

protection may last 1 to 2 years. That is what is great about the information being gathered by 

Pfizer and real-world evidence to help inform that. He also has heard the other contending view 

such as from people in the last VRBPAC meeting who said that protection may drop again right 

after the third dose and it does not cement itself as a 3-dose series. He thinks this will be driven 

largely by what is found in retrospect as more information is gathered about protection.

Dr. Sanchez emphasized the importance of having a surrogate marker. He asked whether there 

are any plans to assess the antibody levels at the time of breakthrough cases to ascertain 

whether there is any association with the antibody level and the serum neutralizing titer with the 

cases of breakthrough disease. If booster dosing is going to be decided based on the fact that 

there is waning immunity and lower antibody responses, it is important to know what exactly is 

occurring in terms of the antibody responses. He emphasized the importance of examining 

antibody responses and other immune markers.

Dr. Gruber stressed that there is interest in looking at breakthroughs in any case. Pfizer 

continues to sequence and try to identify the potential that the antibody responses shown and 

the reassurance that they provide is matched by what is seen. He called upon Dr. Philip

Dormitzer, Pfizer’s Chief Science Officer for Vaccines, to comment on future plans for such 

studies.

Dr. Dormitzer indicated that Pfizer is assessing breakthrough infections and the virus. He did not 

know whether they had the serum at the time of the breakthrough infection to be able to assess 

the correlation of the titer at the time of the breakthrough. They are looking at correlates of 

protection by assessing antibody levels and through modeling work as well. For most vaccines 

that have been available for decades, there are not reliable correlates of protection. While they 

will make every attempt to continue to do so, it also is important to set realistic expectations. It is 

clear that protection is multifactorial. Protection is seen before there are significant neutralizing 

titers and after neutralizing titers fall to very low levels. Protection against variants does not 

correlate well with the level of antigenic escape. That is not to say that neutralizing titers are not 

important. They are probably an overall indicator of overall immune response. However, even 

when neutralizing titer is seen it is not clear whether it is the neutralizing antibody that is 

protecting or the associated CD8+ or CD4+ T-cell responses or non-neutralizing antibodies 

active in antibody-dependent cellular cytotoxicity (ADCC). It is important as a general indicator 

of immune response, but he does not believe that there is going to be a precise correlate of 

protection, as is true for almost all current vaccines.
ACIP Meeting Summary September 22-23, 2021

12

Dr. Lee added that Dr. Thornburg’s presentation would go over this particular topic, after which 

this discussion could continue. She commented that from a safety perspective, the duration of 

follow-up is less important to her than a sufficient sample size in the clinical trials. Duration is 

incredibly important from an efficacy perspective, so she understood the need for both. 

However, she wondered whether it is possible to consider a study that would collect blood 

approximately 2 to 3 days post-vaccination in the window of myocarditis. She said she asked 

because a better understanding is needed of the pathophysiology of what might be contributing. 

Because of the way blood is collected at Day 0 and Day 7, that window is missed. This could 

capture more information in terms of how that relates to systemic reactogenicity and the 

potential for understanding risk factors for myocarditis.

Dr. Gruber emphasized that Pfizer is very attentive to trying to figure out how the potential risks 

can be better identified for even this very rare outcome. They have had discussions with the 

FDA about how best to do that. One way would be to identify a circumstance where an 

individual seems to be having symptoms that could be associated with myocarditis. As part of 

that guidance, they are urging investigators to do a comprehensive work-up that includes getting 

an appropriate blood specimen at that time with the symptoms. One of the challenges is that 

across the literature, there is not a lot that offers confidence in terms of the age groups and the 

specificity of troponins when they are seen and whether it represents a cardiovascular outcome. 

One study they have referenced indicated that two-thirds of the time, an individual presenting 

with non-cardiac symptoms were more likely to have a positive troponin in the absence of a 

cardiovascular finding than in the presence of a cardiovascular finding. The specificity is not 

particularly good. One thing they are considering is obtaining specimens on the existing 

samples to get baseline rates across the population before they are vaccinated in order to better 

define what should be looked for after vaccination. The last thing they want is a non-specific 

signal that just creates further confusion about that risk. They agree that focused attention on 

patients experiencing chest pain, palpitations, and fever in association that suggests a cardiac 

event is important and they are encouraging investigators to do comprehensive work-ups. For 

the rest, more information is needed to avoid going down a path that leads to more confusion by 

testing for things that do not have specificity. Pfizer is in a position of working with the FDA 

about the appropriate obtaining of samples. They do not want to test them prematurely until they 

know that they have some specificity.

Dr. Gluckman (ACP) asked whether anything can be gleaned from the first two doses of 

administration regarding anaphylaxis as it applies to the third dose in terms of whether the 15-

minute wait period in a provider setting is still necessary for those who did not have an 

anaphylactic reaction. That will have implications for workflow as vaccines are administered in 

the provider setting. While it was comforting to see that after a third dose there is still a high 

level of neutralizing antibody from the Delta variant, he was interested to know whether Pfizer is 

working to modify their vaccine for variants and how soon they would be able to get something 

to market if there needs to be a modification of the vaccine to address a variant for which it is 

less effective.

Dr. Gruber responded that they are reassured that they did not see anything in this sample that 

would indicate a higher risk of anaphylaxis. He still thinks it is prudent, as with any vaccine, to 

monitor after the third dose just as is done after the second dose. In terms of potential future 

variants of concern, as part of this trial though not presented here, they looked at the Beta 

variant as a basis for a surrogate. Those data are outstanding because the focus was on the 

current vaccine. Pfizer has had appropriate interactions with the FDA that encourage them that 

looking at the Beta variant as a surrogate, if they can show that there is an appropriate safety 

profile and immune responses are generated to that Beta variant that are comparable to those 
ACIP Meeting Summary September 22-23, 2021

13

that are associated with protection from the original 2-dose series with the original vaccine, that 

would be a basis for approval not only for that vaccine, but also would put them in a position not 

to have to conduct clinical trials for each new variant. Pfizer has in the works the potential to 

pivot very quickly if a variant of concern appears in the future that suggests it is escaping 

protection, and they are setting themselves up to be able to inform that decision based on the 

current trial and those results are forthcoming.

Dr. Fink (FDA) clarified that FDA has had discussions with vaccine manufacturers about data 

that eventually could support a seasonal influenza strain change type approach that would not 

rely on clinical data to support the safety and effectiveness of a strain change. The FDA has not 

concluded at this time that a single example based on a single modified vaccine would be 

sufficient to get there.

Adaptive Immunity and SARS-CoV-2

Dr. Natalie Thornburg (CDC/NCIRD) presented on adaptive immunity after SARS-CoV-2 to 

vaccination with a focus on adaptive cellular and humoral immunity and how they are 

generated, correlates versus contributors to immunity, immune durability and waning, agerelated immunosenescence, and how variant circulation might affect immunity. When one is 

exposed to a virus or vaccinated, an adaptive immune response is activated. That adaptive 

response generates T helper cells from a pool of naïve cells. Those T helper cells drive 

cytotoxic T cells, which kill infected cells and also drives differentiation B cells, which secrete 

antibodies. All of these cells are considered part of the cellular immune response or CMI, and 

the antibodies that the B cells secrete are part of the humoral immune response.4

There are several different isotypes of immunoglobulins or antibodies. Antibodies are simply 

proteins and all proteins have half-lives. Each isotope has an approximately different half-life. It 

is known that serum antibody responses wane according to the half-life of the specific 

immunoglobulin. Antibody responses are expected to wane at a typical half-life decay curve.

Even after antibodies wane, there is still residual adaptive immunity. During the process of 

driving CMI and antibody secretion, memory B cells and memory T cells are developed that are 

virus-specific, can be very long-lived, and can actually live for the life of the person. Then if one 

is re-exposed to antigen either through revaccination or infection, those memory B cells can 

rapidly expand in a germinal center response called an anamnestic response. As part of that 

response, antibodies can be freshly secreted to boost the infected or vaccinated person. Those 

antibodies can be binding antibodies that can be functional neutralizing antibodies, but this 

process can take a few days or a week. In the process, the lymph nodes swell because that 

happens in the germinal center reaction, and there may be some symptoms. When one has that 

amnestic response, the new immune response can then quickly clear of any infection that has 

established itself. Therefore, it is more self-limiting than a primary exposure or a primary 

infection.5

In terms of correlates to immunity versus a contributor to immunity and what is meant by the 

word “immunity.” Immunity is not simply a binary protected versus unprotected, especially with 

regard to upper respiratory infection (URI). There are levels of protection between full sterilizing 

protection and the full disease process. The top level of protection might mean true sterilizing 

immunity and no protection might mean very serious infection or death for some individuals. In 

between those two levels could include asymptomatic infection, symptomatic URI, symptomatic 

4 https://www.virology.ws/2020/11/05/t-cell-responses-to-coronavirus-infection-are-complicated/

5 Roda et al. Cell
ACIP Meeting Summary September 22-23, 2021

14

lower respiratory infection (LRI). There might be different immunological contributors within each 

level that could include, but not be limited to, the level of antibody, antibody isotypes that a 

person has generated, the functionality of those antibodies (binding versus neutralization), the 

specific epitopes of those antibodies and their affinity, physical locations in the body (nose, 

lungs, serum), the number and specificity of the antiviral T cells and B cells, and the ratio of 

different kinds of T cells that have been generated. Any or all of these contributors could be a 

correlate if found to be easily measurable and can predict any state of immunity. However, a 

correlate is not the entire picture. The picture is very complex and dynamic.

Speaking specifically of SARS-CoV-2 and potential correlates, primate models that suggest that 

very high levels of neutralizing antibodies alone are sterilizing and that lower levels can protect 

or abrogate lower respiratory tract infection. A manuscript published by Dan Barouch’s group 

shows rhesus macaques that have received passively transferred neutralizing antibodies from 

previously infected mechanics at high, medium, low, and no neutralizing titers. Transferring very 

high doses of neutralizing IgG to naïve macaques is enough to protect them from lower 

respiratory tract infection. An even lower dose partially protects the animal. Similar but less 

dramatic results are seen in the upper respiratory tract.6

There is emerging evidence to suggest that anti-spike and neutralizing antibodies, which are 

also directed against the spike protein, are correlates of risk. Three studies that are either 

published or in pre-print all identify neutralizing or spike-binding levels as at least partially 

protective. The Khourey et al.7 manuscript compared neutralizing antibody titers after 

vaccination with a multitude of different products, normalized them to convalescent sera, and 

then compared the vaccine efficacy (VE) or the protective efficacy of each of these different 

products and use those normalized values to estimate the level of neutralizing antibodies 

required for about 50% protection against infection. A Goldblatt et al. pre-print that was recently 

published looked at both binding and neutralization assays in participants who had received

Pfizer BNT162b, Moderna mRNA1272, AstraZeneca AZD1222, or Janssen Ad26Cov2.S and 

used a population-based method to estimate a protective threshold, which they predicted at 60 

BAU/ml anti-spike IgG.8 Feng et al., AstraZeneca’s pre-print, calculated levels of binding and 

neutralizing antibodies required for 50%, 60%, 70%, 80%, and 90% percent vaccine 

effectiveness from symptomatic infection after vaccination with their product.9

Peter Gilbert and the NIH Study Group also has done a correlates of risk analysis on the 

Moderna product. They have looked at Day 29 and Day 57 correlates examining inhibitory 

concentrations with neutralization assays, and they also looked at binding assays. As stated in 

the previous presentation, they already estimated VE to be about 45% to 60% in vaccine 

recipients at the early time point—even before they could detect binding or neutralization 

antibodies. So, there was some protection before antibodies could be detected. VE increased to 

greater than 98% in the recipients who had the highest neutralization titers, suggesting that very 

high neutralization titers do contribute to some level of protection. They performed an analysis in 

which they were able to estimate the proportion of protection they saw from the antibody 

response and estimated that at the Day 29 timepoint, about 68% of VE against symptomatic 

infection was mediated through neutralization titers.

10 They have performed similar analyses 

6 https://doi.org/10.1038/s41586-020-03041-6

7 Khoury, D.S., Cromer, D., Reynaldi, A. et al. Neutralizing antibody levels are highly predictive of immune protection from 

symptomatic SARS-CoV-2 infection. Nat Med 27, 1205–1211 (2021). https://doi.org/10.1038/s41591-021-01377-8

8 Goldblatt et al. A Population-Based Threshold of Protection for COVID-19 Vaccines; NaturePortfolio; under review.

9 https://www.medrxiv.org/content/10.1101/2021.06.21.21258528v1

10 Gilbert et al. medRxiv
ACIP Meeting Summary September 22-23, 2021

15

using influenza vaccines and found that, at least with H3, about 57% can be predicted by 

hemagglutination inhibition assays. These data suggest that high titers of anti-spike or 

neutralizing antibodies contribute to immunity. The correlates analysis from the Moderna Phase 

3 trial would suggest about 68% of the VE for symptomatic illness is from neutralizing antibody, 

which would leave about 32% contribution by other immunological factors.

Going back to some of the primate challenge models from the same manuscript shown earlier

from the Barouch laboratory, they let the antibodies of previously infected macaques wane or 

decay to just below what they estimated to be a protective threshold and then re-challenged

them. Before they re-challenged them, they left the animals alone so that they had cellular 

immunity and very low levels of antibodies or depleted their CD8+ T cells. Animals with CD8+ T

cells intact had very little viral replication, so CD8+ T cells contributed to protection of those 

animals. With depleted CD8 T cells, they saw more virus replication. This indicated that both low 

levels of antibodies and CD8 T cells contributed to protection of these animals.

Given the high level of community transmission being seen for SARS-CoV-2, Dr. Thorburg 

discussed what happens if a vaccinated person becomes infected with asymptomatic or 

symptomatic infection. A pre-print looking at 161 infections in vaccinated people was published 

out of the UK during a time of high Delta transmission, so most of these cases were Delta, 

compared the recovery of live virus in unvaccinated versus vaccinated health care workers

(HCW). These investigators saw lower probability of recovering live virus from vaccinated HCW. 

However, they did recover a lot of virus from HCW. There are similar data generated locally that 

corroborate these results, indicating that people who are vaccinated and then have an infection 

are able to shed live, culturable virus, suggesting that they might be infectious.11

Antibodies are expected to wane, which has been confirmed among Pfizer BNT162b2

vaccinated persons. Two different studies examined serum antibody waning in two different

populations of individuals. The first by Naber et al published in The Lancet Regional Health 

Europe Journal12is a longitudinal cohort of 122 participants comprised of HCW 21 to 69 years of 

age with a median age of 36 looking at binding antibodies. Those who received the vaccine had 

significant lower serum antibody titers at 6 months post-boost 2 than they were 1 week after the 

second dose. These are binding not functional antibodies. Data posted in a pre-print followed 

participants out to only 3 months, but they did see neutralizing antibody titers. They found 

waning in both neutralizing and binding antibodies between post-Dose 1 and Dose 2, and more 

heterogeneity in the neutralizing antibody responses with a similar waning rate. By the last time 

point, they had several participants who were approaching the limit of detection.13

Cellular immunity is expected to be longer lived and there is now emerging evidence to

conclude that mRNA vaccine recipients maintain spike-specific memory B cells at 6 months 

after mRNA vaccination. A pre-print article of Moderna recipients who were vaccinated alone or 

who were previously infected and then vaccinated, looking out to about 6 months, showed that 

the vaccine only recipient group had an increase in spike-specific memory B cells at 3 months

and 6 months.

14 Another pre-print of memory B cells in Pfizer recipients showed that between 3 

months and 6 months post-boost, there was an increase in some individuals and at least 

maintaining of memory B cells between the 3-month and 6-month time points.

15 These two pre11 Shamier et al. medRxiv

12 Naber et al; The Lancet Regional Health—Europe

13 Maeda et al., edRxiv

14 Goel et al. bioRxiv

15 Ciabattini et al. medRxiv
ACIP Meeting Summary September 22-23, 2021

16

print studies used different assays and different laboratories, so the results should not be 

compared to each other. BNT162b2 mRNA vaccine recipients generate spike-specific early 

memory CD8+ T cells based on a study looking at memory T cells in Pfizer recipients that was 

published in Nature. This study used three different peptides to detect memory to T cells and 

collected peripheral blood mononuclear cells (PBMCs) from these individuals after 80 days 

post-vaccination. In most Pfizer recipients, they were able to detect early memory T cells after 

vaccination.16 To summarize durability, serum antibodies decrease over time, memory B cells 

are maintained out to 6 months post-vaccination, and early memory T cells are generated and 

detected after vaccination with the Pfizer-BioNTech product.

Given that immune responses in all age groups probably will not be the same, the process of 

immunosenescence is important to address. At first, people have a large thymus and a very 

large pool of naive T cells and as immune systems are educated by vaccination and infections, 

pools of memory T cells are built against antigens to which a person has responded. As people 

age, the thymus shrinks and the pool of naive T cells dwindles, but the memory B cells and 

memory T cells of all antigens encountered throughout life are maintained.

17 In terms of what 

that means for someone who is exposed to a new antigen who has limited naive T cells, this 

entire process can be abrogated. If someone does not have naïve T cells to differentiate virusspecific T helper cells, they can have abrogated differentiation of cytotoxic T cells to clear 

infected cells and aggregated differentiation of B cells and secretion of antibodies.18 There is a 

publication in Nature by Collier et al.19 looking at age-specific immune responses to Pfizer 

vaccination. In this, they have assessed both humoral and cellular immunity.

In terms of data from humoral immunity, they looked at neutralizing antibodies after one dose 

and the probability of having any detecting neutralizing antibody and that plotted against age. 

Probability starts to decline right around 50 years of age, slowly declines to about 80 years of 

age, and then drops off very quickly after 80. After a prime and boost, there is a statistically 

significant difference in the 50% serum neutralization tighter in adults greater than 80 years of 

age versus those less than 80 years of age. For cellular immunity, Collier et al. found that adults 

greater than 80 years of age also have less mature antibodies and fewer functional T cells, so 

abrogated CMI. In terms of mutations in the antibody genes in their B cells, meaning how 

specific that B cell has been driven to be directed toward the virus, a fewer number of mutations 

means it is closer to their germline or their own genes and just not as specific. They have a 

statistically significant fewer number of mutations—so less mature. There is a statistically 

significant difference between those less than 80 years of age and those older than 80 years of 

age and the two different T cell secreting cytokines.

Antibodies wane, cellular memory is maintained, and older adults are prone to 

immunosenescence. They have lower neutralizing antibody titers and, as predicted, less robust 

cellular immunity—probably due to immunosenescence. Therefore, they may need to rely more 

heavily on humoral immunity. This is a very complex situation for them. In addition, there are 

variants circulating that may affect immunity overall. Decay of neutralizing antibodies could be 

confounded by the circulation of variants of concern or variants of interest. Some variants have 

amino acid changes near the spike receptor binding domain that could result in reduction in 

neutralization titers. Many groups have tested many different variants and their ability to be 

neutralized by post-vaccination and convalescent sera and have found that neutralization loss 

16 Oberhardt et al. Nature

17 Candia et al. Trends in Immunology

18 https://www.virology.ws/2020/11/05/t-cell-responses-to-coronavirus-infection-are-complicated/

19 https://www.nature.com/articles/s41586-021-03739-1
ACIP Meeting Summary September 22-23, 2021

17

ranges from none, which is an Alpha B.1.1.7 to about 7-fold Beta, which is B.1.351. Delta 

demonstrates an approximately 1.5 to 2 full reduction in neutralization titers.20

Examination of antibody waning in young healthy individuals vaccinated with mRNA over the 

course of about 6 months is specific to variants rather than PfizerBioNTech-vaccinated 

individuals. While the kinetics of waning might be different with the Pfizer product, neutralization 

differences should be approximately the same because the antigen design is very similar.

B.1.351 has the most dramatic loss of neutralization. At peak titers, it is significantly lower than 

the ancestral strain or the vaccine strain (WA1). They all decay at approximately the same rate, 

but end up with a functionally lower tighter against a variant of concern like Beta just because of 

the lower initial titers. It is reaching the lower limit of detection by 6 months post-vaccination.

Given that older adults have lower antibody titers at peak, they have lower antibody titers 

against the variants. Older adults have lower neutralization titers against many of the variants. 

At 6 months looking at three different age groups (18 to 55; 56 to 70; and 71+), there is loss of 

neutralization against Beta B.1.351 such that several individuals in all age groups drop below 

the limit of detection.21 In terms of CMI against variants, the good news is that in three different 

population of T cells in individuals vaccinated with PfizerBioNTech product there is no statistical 

difference seen in any variant. Thus, T cell activity is maintained against all of the variant spikes 

that have emerged so far.22

In conclusion, there is a degree of protection from different outcomes based on a person’s level 

of immunity. Multiple components of the immune system are required to prevent infection and 

illness. These components are complex and dynamic. When a vaccinated person becomes 

infected, they may shed culturable virus and therefore could be infectious. Antibodies decrease 

over time as expected in all age groups, but cellular memory is maintained after weaning.

Neutralizing antibodies likely confer a majority, but not all, of immunity. Cellular responses likely 

contribute to protection against severe disease through anamnestic responses even after 

antibodies wane. Older adults start with lower neutralization titers than younger adults. Because 

they start at lower titers, they may be faster to fall below the limit of detection. They may have 

less robust cellular memory generation because of immunosenescence and therefore may be 

even more dependent on humoral immunity. Reduced neutralization of variant viruses may 

confound antibody waning in all age groups.

Discussion Points

Dr. Poehling requested additional information about the impact of the lower results with regard 

to T cells.

Dr. Thornburg indicated that this was from the Collier et al. Nature paper testing the function of 

the T cells in which they found that in the T cells that were activated, there were fewer T cells in 

the group older than 80 years of age. The T cells that they did generate were not as functional. 

Individuals who had robust responses seemed to be fairly equivalent in those above and lower 

than 80 year of age. There did seem to be more people in the group 80 years of age and above 

who did not have a functional response.

20 Liu et al. Nature

21 Pegu et al. Science

22 Richardson et al. medRxiv
ACIP Meeting Summary September 22-23, 2021

18

Dr. Chen noted that some of Dr. Thornburg’s slides were impressive because they implied that 

there was a dropping off effect with age, which looked like about 80 years of age. Another slide 

implied that there was a drop off of the cell-mediated response around 70 years of age. He 

asked whether these data or other data would help to better define an age cutoff for a riskbased strategy for vaccine implementation if the population had to be prioritized. Some data 

suggest that 70 or 80 years of age and above would be the first priority, while some people 

naturally adopt 65 years of age and older when discussing older adults. However, that is 

somewhat arbitrary as a cutoff. He also asked whether there are data that Dr. Thornburg did not 

present that suggest an additional contribution for certain comorbidities (e.g., cancer, kidney 

patients on dialysis, and other groups) that would help to navigate how to develop a risk-based 

recommendation.

Dr. Thornburg agreed that finding a cutoff is very challenging in terms of when 

immunosenescence kicks in. She thinks the answer is that this occurs gradually over time. It 

seems to be a gradient versus a dramatic cutoff. These studies do not help with that cutoff 

because they are small by need. These are very difficult, laborious assays that do not allow for 

population-base studies. These studies also looked at fairly healthy older adults, so there are 

not a lot of comorbidities. Perhaps a comorbidity is driving this phenomenon because there are 

a few who just do not respond at all.

Dr. Daley requested a reminder of the difference between binding antibodies and neutralizing 

antibodies and then a relationship to how that is interpreted in immunogenicity studies from 

Phase 3 clinical trials that report antibody GMT titers.

Dr. Thornburg replied that neutralizing antibodies are a subset of binding antibodies. Binding 

assays detect just that process. There is protein stuck on a bead or plastic and any antibody 

that binds anywhere on the spike protein is binding antibody. The assays detect functional and 

non-functional antibodies, but these are easier and faster than neutralization assays. 

Neutralizing antibodies are a subset of binding antibodies, so all of the antibodies have to bind 

the spike and most of them have to bind the right part of the spike, usually around the receptor 

binding domains, which bind spike and block the virus from entering a cell. They spherically 

inhibit the virus from binding and entering the cell. The reality is that the actual contributor to 

immunity is probably neutralization assays. However, those are difficult and laborious and 

binding assays are much easier and have less variation between laboratories. If a binding 

correlate can be found that benefits everyone, studies can be normalized and compared. In 

terms of the differences being seen in neutralization and binding between different vaccine 

products, there are also differences in the ways that the antigens have been designed and 

delivered. There probably is a real difference in the proportion of binding antibodies to 

neutralizing antibodies that each one of these vaccine products drives.

Dr. Long pointed out that immunology is so complex, she wanted to make a couple of 

comments so that people might not oversimplify what had been said or apply it maybe hastily.

People like to measure antibodies because it is easier to do. While it is known that this is not the 

full story, it is convenient. The idea that antibodies wane is true and not true in reference to 

certain vaccinations. As a rule, antibody is not measured 1 or 2 months after vaccine but is 

measured at 4 months or 6 months because the initial responses are going to wane. However, it 

depends on what kind of lymphocytes are invited to the vaccine party that determines whether 

there will be some level of sustained antibody response as there must be without an anamnestic

response from seeing an organism again for a lot of vaccines that are not live and that are not 

latent in the recipient that produce long-term immunity. There are many examples such as 

Hepatitis A and B and pneumococcus might be another. If there are only antibody responses 
ACIP Meeting Summary September 22-23, 2021

19

that wane, it would be all gone. If there are lymphocytes that are participating that change the 

immunologic reaction so that there is a sustained or new production of some level of antibodies, 

that is what one is looking for and for many vaccines that is the case. The fact that these high 

antibodies wane probably does not have any meaning, except that only very high antibodies 

administered to a macaque can prevent them from symptomatic disease. In terms of a mucosal 

infection, which coronavirus is, there is never going to be discussion about sterilizing immunity. 

They will be talking only about controlling symptoms because an order is being given for spike 

protein parenterally to prevent an infection. Therefore, instead of caring about whether antibody 

wanes, more important is the minimum needed to have protection. Even the statement that very 

high levels of neutralizing antibody are protective is not known except in the macaque model 

when they had only antibodies. Therefore, it is not clear whether it is the antibodies or is the 

association that allows one to have high sustained antibodies. She thinks this will become 

important as they go down the line about boosting.

Dr. Talbot said she thought Slide 8 was critical in terms of moving forward with the pandemic. 

Coronaviruses often become endemic and it is highly unlikely that all mild or symptomatic 

respiratory infections will be prevented. Showing the spectrum of disease along with the 

spectrum of immune responses is incredibly important. It is important to understand that 

hospitalizations and deaths likely will be prevented, hopefully along with symptomatic 

respiratory infections. However, it is unlikely that everything will be prevented.

Vaccine Effectiveness Studies in the United States

Dr. Ruth Link-Gelles (CDC/NCIRD) presented a summary of VE data available from CDC 

platforms or published via CDC’s Morbidity and Mortality Weekly Report (MMWR). CDC uses 

multiple platforms and study designs to monitor COVID-19 VE. These designs monitor both 

duration of protection and protection against variants by risk groups, outcomes of interest

(infection, severe disease, hospitalization), and products. While not every platform has the 

sample size to cut data by all these categories, CDC has attempted to present data during this 

session from each platform in a way that will be most meaningful for the questions at hand while 

not cutting the data too finely.

The first platform, the Increasing Community Access to Testing (ICATT) Partnership, does not 

specifically focus on any populations of interest. However, with nearly 1 million observations 

from the general population, it allows the unique opportunity to truly tease apart waning against 

infection pre-Delta and during Delta. Therefore, it was included in this presentation for 

background. The ICATT platform includes community-based testing data from pharmacies and 

partners nationwide. It uses a test-negative design and importantly, vaccine history is selfreported. For this analysis, only individuals reporting symptoms were included. Data are 

presented here for ages 20 to 64 and adjusted for time, race, ethnicity, gender, HHS region, 

state, and site census tract Social Vulnerability Index (SVI). No adjustment is available for 

underlying conditions or prior infection.

Dr. Link-Gelles showed a series of graphs of VE against symptomatic infection by age group for 

each vaccine. Starting with Pfizer, waning can be seen in both time periods of pre-Delta and 

Delta, with lower VE and more waiting during the Delta period. The curves look similar for all 

age groups, with a VE around 65% by 200 days after the second dose. Moderna VE tends to be 

roughly 5% to 10% percent higher for each age group compared to Pfizer, with VE between 

65% and 75% by 200 days after the second dose. The same general pattern is seen with more 

waning and lower VE during Delta was seen with Pfizer. Again, the patterns are similar across 

the age groups. For Janssen, VE increases by time since vaccination, which matches the data 
ACIP Meeting Summary September 22-23, 2021

20

from the Janssen RCT. The effect of Delta here is a little murkier and there was less pre-Delta 

follow-up due to the later rollout of Janssen. The curve for Janssen looks similar across age 

groups, with VE 200 days after vaccination during Delta up to around 55% or about 10% lower 

than Pfizer.

As ICATT is such a large dataset, it is important to carefully highlight the limitations, including 

self-reported vaccine history, which resulted in dropping about 18% of the data. There are no 

data on co-morbidities, prior infection, or behaviors. Since there are no individual level unique 

identifiers, analyses are based on text rather than individual people. Finally, there are no genetic 

sequencing results so time is used to differentiate Delta from non-Delta.

Focusing now on platforms that include data on individuals ≥65 years of age, including residents 

of long-term care facilities (LTCFs), COVID-19-Associated Hospitalization Surveillance 

Network (COVID-NET) is a population-based surveillance system that collects data on 

laboratory-confirmed COVID-19 hospitalizations through a network of over 250 acute care 

hospitals in 14 states. The case definition is “a resident of the surveillance area with a positive 

SARS-CoV-2 test within 14 days prior to or during hospitalization.” Using immunization registry 

data, investigators estimated VE against hospitalization during April to August 2021 by age 

group. VE was calculated using a variation of a screening method through a Poisson regression 

model that allows control for calendar time. Importantly, this method does not allow for 

adjustments for other important confounders, including co-morbidities and prior infection.23

In terms of VE for the mRNA products by age group over time during April to August 2021 from 

COVID-NET, these data represent Pfizer and Moderna vaccines combined. However, 

approximately 71% of the vaccinated cases shown received Pfizer. This may be an artifact in 

that most residents of LTCFs participating in the federal distribution program received the Pfizer 

product. VE remained well above 90% and highly overlapping for all ages up to 74 years, but 

trended lower starting in June for those 75 years and older. VE for this age group was around 

88% July and 91% in August.24

COVID-NET gets detailed clinical and vaccination status on a representative sample of patients

on a monthly basis, excluding partially vaccinated patients and those who are fully vaccinated 

but had evidence of prior SARS-CoV-2 tests. These included almost 6000 cases, of whom 92% 

were unvaccinated. In terms of the characteristics of unvaccinated and fully vaccinated

hospitalized cases, there were statistically significant differences in demographics and 

underlying medical conditions. In general, fully vaccinated persons were more likely to be older,

with a median age of 72 compared to 59 unvaccinated persons; and 72% of breakthrough cases 

from January to July 2021 were greater than 65 years of age compared to only 40% among 

unvaccinated cases. Vaccinated cases also were more likely to be residents of LTCFs and more 

medically fragile, as evidenced by significantly higher proportions of people who had a Do Not 

Resuscitate/Do Not Intubate (DNR/DNI) code status on admission and more underlying 

conditions. Additionally, COVID-NET found that the number of underlying conditions were 

higher in fully vaccinated persons, with half of the vaccinated persons having cardiovascular 

disease (CVD) compared to only a third in non-vaccinated persons.

23 Vaccine effectiveness calculated using previously described methods: Moline et al. Effectiveness of COVID-19 Vaccines in 

Preventing Hospitalization Among Adults Aged ≥65 Years — COVID-NET, 13 States, February–April 2021. MMWR, August 13, 

2021

24 Unpublished COVID-NET data, 2021
ACIP Meeting Summary September 22-23, 2021

21

The New York State Department of Health recently published an MMWR using linked 

laboratory, immunization, and hospitalization records.25 Dr. Link-Gelles shared an update of 

their analysis that includes over 150,000 observation. Over 90% of their population received 

mRNA products. There was a decrease in VE against infection in June and July 2021 for all age 

groups as Delta surged and then a leveling off of VE against infection in July and August. VE 

against hospitalization remained relatively stable for all age groups, with a slight decline for the 

65 plus age group during the Delta period.

VISION is a multi-state network including electronic health records (EHRs) from 187 hospitals. 

VE was calculated for adults 18 years of age and up, with the investigators comparing 

hospitalized individuals with COVID-like illness (CLI) with polymerase chain reaction (PCR)-

confirmed SARS-CoV-2 infection versus virus negative controls. VE was adjusted for propensity 

to be vaccinated, calendar time, region, local virus circulation, and age. Models for waning used 

6 of the 7 total VISION sites. Vaccination is documented in EHRs and jurisdictional 

immunization registries. Fairly stable VE was seen in the two time periods, pre-Delta versus 

Delta, with the exception of the 65 plus and a bigger decrease specifically for Pfizer with nonoverlapping confidence intervals. While there is a hint of decrease for the Moderna point 

estimates in this age group, this was not statistically significant. VISION has VE against 

hospitalization for all adults by time period of January to March, April to May, and June to 

August and then subsetted by time since vaccination looking at 14 days to less than 2 months

since vaccination all the way to 5 plus months since vaccination. Among people recently 

vaccinated, VE against hospitalization remained high at all three time periods. In the Delta 

period from June to August, VE has declined among those who have been vaccinated for longer 

periods of time, with a statistically significant decreasing trend. Waning is expected to be the 

same or worse in older adults.

Given that there are so little data on Janssen, Dr. Link-Gelles shared a comparison of the preDelta and Delta period pulled from previous publications. Due to small numbers, VISION was 

not able to show a specific 50 plus estimate during Delta. A decrease was seen in the point 

estimate for VE, although with wide confidence intervals. If anything, the comparison of an older 

age group in pre-Delta to younger age groups during Delta would bias towards less decline.

26

The National Healthcare Safety Network (NHSN) is a healthcare data reporting system. For 

COVID-19, nursing homes report both the number of residents in the facility and the number of 

COVID-19 cases in residence by vaccination status on a weekly basis. Investigators estimated 

VE for infection for 3e periods: Pre-Delta (March 1-May 9), Intermediate (May 10–June 20), and 

Delta (June 20–Aug 1). Reporting to the platform became mandatory in June for the Centers for 

Medicare and Medicaid (CMS)-certified skilled nursing facilities (SNFs), so the number of 

facilities reporting rose steadily during the study period.27 In terms of the results for each of the 

periods, VE for both, products declined from almost 75% in the pre-Delta period to 53% in the 

Delta period and did not differ substantially by product.28

25 https://www.cdc.gov/mmwr/volumes/70/wr/mm7034e1.htm

26 https://www.nejm.org/doi/full/10.1056/NEJMoa2110362 and https://www.cdc.gov/mmwr/volumes/70/wr/mm7037e2.htm

27 https://www.cdc.gov/mmwr/volumes/70/wr/mm7034e2.htm

28 Adapted from: Nanduri S. Effectiveness of Pfizer-BioNTech and Moderna Vaccines in Preventing SARS-CoV-2 Infection Among 

Nursing Home Residents Before and During Widespread Circulation of the SARS-CoV-2 B.1.617.2 (Delta) Variant — National 

Healthcare Safety Network, March 1–August 1, 2021. MMWR Morbidity and Mortality Weekly Report. 2021 2021;70. Slide 

courtesy of Ian Plumb
ACIP Meeting Summary September 22-23, 2021

22

In summary for individuals 65 plus, large declines were seen for mRNA products against 

infection. The largest decline was from the platform focused on the LTCF residence, although 

New York State also reported a decline from 91% to 75% for all adults 65 plus. 

Data for VE against hospitalization were more mixed. VE remained relatively high in all 

platforms, with a larger decline for Pfizer and 65 plus versus the two mRNA products combined

or Moderna alone.

Moving to VE estimates in individuals with underlying conditions, including data on individuals 

65 plus when included in these platforms, the SUrveillance Platform for Enteric and 

Respiratory iNfectious Organisms at the VA (SUPERNOVA) Network is a sentinel surveillance 

network of 5 Veterans Affairs Medical Centers. From February 1-July 31, 2021, investigators 

conducted a case-control VE assessment using data from these sites. Eligible participants were 

US Veterans at least 18 years of age who were hospitalized in any of these 5 sites. Cases were 

defined as “patients with CLI who tested positive for SARS-CoV-2 by reverse transcriptase 

polymerase chain reaction (RT-PCR). Controls also were patients with CLI with negative SARSCoV-2 test results. Of note, while SUPERNOVA does not specifically target elderly individuals

or those with co-morbidities, given the general VA population, this group is skewed in that 

direction with a median age of 67 years and almost half the CCI above 3. This estimate is 

included in the group who may be at higher risk of severe COVID-19 due to underlying 

conditions. For the entire study, not divided by Delta predominance and with Pfizer and 

Moderna combined, there was a statistically significantly lower VE for older individuals. Pfizer 

has a more extreme difference between age groups. Neither of the differences in individual 

products was significant. Estimates broken down by Delta predominance and times since 

vaccination include all age groups and both mRNA products. Little change is seen in VE and 

hospitalization by time period or by time since vaccination.29

The Influenza and Other Viruses in the Acutely Ill (IVY) Network is an active surveillance 

network of 21 sentinel hospitals in 18 states. Sites enroll hospitalized adults with and without 

CLI, rapidly collect in-depth vaccination, critical information, and respiratory samples for central 

RT-PCR testing and sequencing. PCR-positive cases are matched with PCR-negative controls. 

For this analysis of VE against hospitalized COVID-19, IVY investigators included adults 

admitted to IVY sites from March 11-August 15, 2021. For Pfizer, the difference for time since 

vaccination by time period was both contextually meaningful and statistically significant. 

Moderna did not show similar waning. There were not enough observations to break out 

Janssen by time since vaccination, but the overall estimate was included for comparison. With

Pfizer and Moderna estimates combined and then separated by age group of under 65 years of 

age and over 65 years of age, a decline is seen in the 65 plus age group. No similar decline is 

seen in the younger adults. In the same age groups by pre-Delta versus Delta instead of time 

since vaccination, there is a less pronounced decline in the 65 plus age group. Finally, the IVY 

team was able to run some analyses looking specifically at those with co-morbidities in the preDelta and Delta periods. This analysis excludes those with immunocompromising conditions

and controls for age. Although overall VE for individuals with underlying conditions appears

slightly lower than for those with no underlying conditions, no large declines are seen from the 

pre-Delta versus Delta period in any of the age groups. No estimates were available for VE 

against infection for individuals specifically with underlying medical conditions. For VE against 

hospitalization, estimates did not vary substantially by Delta predominance.30

29 https://www.cdc.gov/mmwr/volumes/70/wr/mm7037e3.htm

30 IVY: CDC unpublished data
ACIP Meeting Summary September 22-23, 2021

23

Moving to individuals with occupations that put them at higher risk of exposure to SARS-CoV-2

(grocery workers, educators, restaurant workers, et cetera), estimates for most professions are 

not available. While for this session Dr. Link-Gelles presented data on healthcare personnel 

(HCP), first responders, and other frontline workers, she noted that there should be no biological 

difference in VE between these groups and similar individuals in lower risk occupations.

Healthcare, Emergency Response, and Other Essential Workers Surveillance Study-Research 

on the Epidemiology of SARS-CoV-2 in Essential Response Personnel (HEROES-RECOVER)31

is a prospective cohort of over 4,000 HCP, first responders, and other frontline workers in 8 US 

locations. Participants are swabbed weekly and additional specimens are collected if a 

participant is ill. Vaccination is documented through multiple methods, with 95% of those 

vaccinated receiving an mRNA product. In the full study period by time since vaccination, 

although the confidence intervals are wide, some indication is seen in the point estimates of 

waning immunity over time. A substantial decline is seen in VE against infection from 91% in the 

pre-Delta period to 66% once Delta was predominant. Importantly, there were not enough

hospitalizations in this highly vaccinated population to provide estimates for VE for 

hospitalization.

To summarize the results by risk group, first for the 3 risk groups together to give a sense of 

magnitude, there are many more data available for adults 65 plus. However, there is not much 

reason to think there would be a different VE in the other 2 groups than in other adults. For 

example, a similar decrease is seen in VE against infection for HCP and for 65 plus. Across 

platforms, VE appears to decrease more for infection than hospitalization, although the VISION 

platform did see a decrease in VE for adults against hospitalization—a finding that is not

generally seen in younger age groups. For individual ≥65 years of age, significant declines were 

seen in VE against infection during Delta for the mRNA products. Declines also were seen,

particularly for Pfizer for ≥65 years of age that were not seen in younger populations. Finally, 

there is evidence of waning for VE against hospitalization in the Delta period. While an estimate 

specifically for 65 plus was not available, it is likely that waning for that group would be as bad 

or worse than in all adults. For individuals with underlying medical conditions, there was no 

specific data on VE against infection. However, it is likely that VE for this group is similar to that

In the general population as shown in the ICATT data. VE against hospitalization for those with 

underlying medical conditions remained high in the Delta period. For individuals with 

occupations with high risk of exposure to SARS-CoV-2, there were no data on VE against 

hospitalization specifically. Again, this is likely to be similar to that in the general population. 

Similar patterns were seen for VE against infection for this group as were seen in the general 

adult population.

Discussion Points

Dr. Long suggested not lumping infection and hospitalization, given that there is likely no hope 

that a vaccine such as the ones currently available will prevent infection after the first couple of 

weeks with extraordinary immediate responses. She suspects they will end up saying that the 

ultimate goal of the current program will be to prevent serious symptomatic infections, 

hospitalizations, and deaths. HCP should not be of concern for transmission to others because 

they should be masked and practicing appropriate distancing, hygiene, et cetera. She thinks it is 

confusing for the populous to think that if they can get infected, the vaccine is failing. This 

vaccine is not going to be more than 80% protective against infection just because the only 

protection against infection one gets is what leaches out of the parenteral circulation into the 

mucosa.

31 https://www.cdc.gov/mmwr/volumes/70/wr/mm7034e4.htm
ACIP Meeting Summary September 22-23, 2021

24

Dr. Bell emphasized the importance of keeping the age effect in mind when looking at other 

subgroups.

Dr. Poehling appreciated how many different groups are assessing VE. It appeared to her that 

the SUPERNOVA population was almost 50% Black and had high co-morbidities, so that VE is 

very important in terms of thinking about disparities that are seen with race and ethnicity.

Dr. Brooks found this presentation to be important in terms of showing that there is a waning of 

VE even in the context of T cell protection being high. He asked Dr. Link-Gelles to comment on 

the decrease in VE in HCP, which he presumed to be generally of a lower age than the general 

population or senior population. He wondered if HCP experiencing more exposure and therefore 

more chance of them getting infected might be attributed to the decrease in VE.

Dr. Link-Gelles indicated that in the HEROS-RECOVER data where VE for infection decreased 

from 91% to 66% and a lot of other studies, there is information to show that most of those 

infections are actually community-acquired versus acquired on the job. She also pointed back to 

the ICATT data of the general population in which similar steep declines were observed in VE 

against infection in particular, regardless of age group and in the general population—not 

specifically to HCP.

Dr. Duchin (NACCHO) noted that for the COVID-NET hospitalization data, he did not see 

obesity listed as a risk factor and wondered whether it did not rise to level of increased risk or if 

it was not assessed. In addition, he asked whether the VE studies accounted for prior COVID19 in unvaccinated populations. He also asked Dr. Link-Gelles to comment on some of the 

differences between the data from the US and what has been reported from other countries, in 

particular from Israel.

Dr. Link-Gelles said that while she did not have the number for obesity in front of her, she could 

follow up with it. Most of the studies were able to exclude prior COVID-19 infections. Because 

COVID-NET was using a screening method, the investigators were able to exclude individuals 

who were hospitalized for prior infection. For the non-hospitalized group, they do not have 

individualized data for the comparison group on prior infections because they are using an 

ecological analysis. All of the individual-level platforms (VA, IVY, VISION) exclude individuals 

with prior infection. In terms of the differences in data reported in the US and other countries, 

she noted that Dr. Oliver would include some of the international estimates in her presentation 

later in the day. She emphasized that there are differences between the populations and the 

methods that are used in the analyses in Israel versus the US, with the biggest on being the 

difference in how the US defines severe disease. The Israeli data can include outpatient 

individuals in severe disease based on respiratory rates whereas hospitalization is used almost 

across the board in the US as the definition for severe disease. That will change the estimate 

quite a bit and skew the Israeli estimates a little more toward what the US sees for infection.
ACIP Meeting Summary September 22-23, 2021

25

Dr. Lee observed that it seemed like the Delta variant had a bigger impact in the HCP cohort, 

while in the IVY cohort it seemed like time since vaccination had a slightly bigger impact. She 

wondered whether Dr. Link-Gelles could provide an understanding of what might be most 

relevant in terms of whether it is differences in populations, time variant confounders, or both.

Dr. Link-Gelles said she thought it could be different methodologies and the fact that neither 

HEROS-RECOVER nor IVY was able to truly tease apart time since vaccination from Delta, so 

they were not able to do the cross tabulation of looking at time since vaccination in the pre-Delta 

period and then time since vaccination overall. They looked at time since vaccination in the 

entire cohort and then separately for pre-Delta versus during Delta. That can skew depending 

on the cohort. HEROS-RECOVER focuses on HCP, many of whom would have been 

vaccinated much earlier than the general population included in the IVY analysis. Since preDelta versus post-Delta cannot be teased apart, it is hard to parse out. The clearest one for that 

particular question is the VISION analysis since they actually did have enough observations in 

the Delta period to look at waning over time since vaccination during Delta, and they did see a

significant decrease in trends.

Dr. Weiser (IHS) asked whether any additional data are available for American Indian/Alaskan 

Native (AI/AN) populations with regard to VE or waning. It is known that during the pre-vaccine 

era, AI/AN were heavily impacted—especially at younger ages. Hospitalizations and death 

seemed to peak at a younger age among AI/AN than in the general population.

Dr. Link-Gelles indicated that there is a platform that focuses specifically on VE among AI/AN. 

However, the population is so small that they have not had enough cases in that platform at this 

time to provide estimates.

Dr. Lee expressed appreciation on behalf of the ACIP to Dr. Link-Gelles and her team as well as 

all of the investigators and emphasized that these data are critical to help the ACIP wade 

through the data and understand it better in support of their decision-making efforts.

Modeling the Potential Impact of Booster Doses in Nursing Home Residents

Dr. Rachel Slayton (CDC/NCEZID) presented mathematical modeling of SARS-CoV-2 

transmission in nursing homes. Data on trends in the weekly rate of COVID-19 cases in 

communities and in nursing homes highlight that outbreaks in the community and nursing 

homes are linked and that controlling community transmission is important for protecting the 

vulnerable nursing home resident population. To better understand SARS-CoV-2 transmission 

in nursing homes, CDC investigators developed a model in collaboration with colleagues at the 

Harvard T.H. Chan School of Public Health, in particular with Rebecca Khan and Inga 

Holmdahl, that builds upon previously published work.32 They modeled an average US nursing 

homes with 100 residents in 100 staff members. In this analysis, the nursing home is fully 

occupied, with resident turnover explicitly modeled using resident length of stay data from CMS. 

Cases are introduced into the nursing home by staff, who have a daily probability of infection 

from their time in the community that is directly estimated from NHSN data. Transmission within 

the nursing home is stochastic. It is based on the number of contacts individuals have each day, 

the probability of transmission given a contact with an infectious person, and the total number of 

infectious individuals in the nursing home each day. Following guidelines, non-outbreak

screening testing of unvaccinated staff is conducted twice per week. One an outbreak is 

identified, this shifts to twice weekly tests.

32 https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciab517/6292250
ACIP Meeting Summary September 22-23, 2021

26

The analysis looked at 4 main outcomes over a 2-month period, including the total number of 

symptomatic cases in residents and in the entire nursing home, including both residents and 

staff; and the total number of infections in residents and in the entire nursing home. The 

simulations were repeated 100 times to capture variability. Some key parameters from the 

model include a basic reproduction number of 6, reflecting estimates for the more transmissible 

Delta variant. As previously mentioned, the staff have a daily probability of infection from the 

community, which was varied from moderately high to high. Among residents in the nursing 

home at the beginning of the simulation and those that enter the nursing homes during the 

simulation, 80% are vaccinated. Staff vaccination coverage was varied from 40% to 100%. 

Several values were considered for VE. First, the 2-dose VE against infection for staff was 70%. 

The 2-dose VE against infection was varied for residents from 50% to 70%, reflecting some data 

which showed that there is lower VE among older populations. The vaccine also has efficacy 

against progression to symptoms. It was assumed that VE against symptomatic disease for staff 

was 90% and varied the same parameter between 80% and 90% for residents. VE against

infectiousness or transmission was assumed to be 50% for both residents and staff, which 

means that infections in vaccinated persons are half as infectious as those occurring in 

unvaccinated individuals. The introduction of booster doses also was modeled, which take 2 

weeks to take effect, and their efficacy was systematically varied from 60% to 90%.

Looking at the cumulative incidence among residents after 2 months by symptom status and 

vaccination status in simulations with resident vaccination coverage of 80%, staff vaccination 

coverage of 60%, and no boosters, the distribution of cumulative incidence among residents 

after 2 months across 100 simulations showed that a majority of cases in vaccinated residents 

were asymptomatic due to VE against symptomatic disease. While only 20% of residents were 

unvaccinated in these simulations, they contributed a large share of symptomatic cases. A 

higher daily importation rate resulted in more nursing home cases. This highlights that an 

increase in nursing home cases does not necessarily indicate lower or waning VE if a 

community’s transmission is increasing during the same time period. When VE against infection 

for residents was assumed to be 70%, similar trends were observed. This reflected lower 

cumulative incidence overall, which would be expected when VE is higher.

Next, Dr. Slayton described simulations assessing the impact of varying levels of staff 

vaccination coverage and providing all residents a booster dose with varying VE. Investigators

began by looking at the number of symptomatic cases among residents showing simulations 

with a moderate level of staff importation and a higher level of staff importantation—reflecting 

higher community transmission. In these simulations, no boosters were given and VE against 

infection in residents was 50%. Staff vaccination coverage was systematically varied from 40%

to 100%. As expected, higher staff vaccination coverage resulted in fewer symptomatic cases 

among residents. The cumulative cases were highly dependent on community transmission. For 

context, over the 2-month period being modeled in the 100-bed nursing home, there were 217 

unique residents on average over the entire time period because the median duration of stay 

modeled was 27 days. Across nursing homes in the US, NHSN data finds that the average staff 

vaccination coverage is just above 60%. The impact of increasing staff vaccination coverage 

from above that national average leads to fewer symptomatic cases.

Moving to simulations that include boosters, VE against infection in residences is 50% after the 

booster doses were given to all vaccinated residents staff who were not receiving a booster 

doses in these simulation. As a reminder, 80% of residents were vaccinated and all of them 

received a booster dose, but the efficacy of that booster was varied. The simulations showed 

that boosters increased VE against infection from 50% to 60% in residents. Higher staff 

coverage and higher booster VE against infection leads to fewer symptomatic cases among 
ACIP Meeting Summary September 22-23, 2021

27

residents. Similar to the previous findings, cumulative symptomatic cases among residents were 

highly dependent on the community transmission. Looking at total symptomatic and 

asymptomatic COVID-19 infections among residents, there were higher absolute numbers of 

infections when looking at total infections, but the trends remain largely the same. Once again, 

higher staff coverage and higher booster VE led to fewer infections.

In terms of symptomatic COVID-19 cases in nursing homes overall, including both residents and 

staff, similar trends are seen when looking at all symptomatic cases in the nursing home as 

compared with looking at residents only. Of note, there was a larger impact of increasing staff 

coverage because this incorporated the direct protection the vaccines provided to the staff in 

addition to the indirect protection that vaccination provides to nursing home residents. Looking 

at total infections, including asymptomatic and symptomatic infections in the nursing home 

overall including both residents and staff, similar trends were seen as when looking at total 

infections in residents. However, there were higher numbers of infections than previously 

shown.

This analysis is subject to a number of limitations. The investigators modeled VE against 

infections, VE against symptomatic disease, and VE against infections as point estimates. 

These estimates are likely to vary by a number of factors (e.g., vaccine type, age of vaccinated

persons, and immunocompromising conditions of vaccinated persons). The analysis shown is 

most appropriate when we considering the potential impact of providing booster doses for 

nursing home residents who received an mRNA vaccine. An average nursing home was 

modeled, which did not capture all facility-level heterogeneity. Additionally, previous COVID-19 

infections were not explicitly modeled, which may have underestimated the level of prior 

immune protection independent of vaccination. In addition, the impact of vaccine supply 

shortages were not explored in this model.

In summary, maximizing vaccination coverage among nursing home staff remains a critical tool 

for preventing cases in nursing home residents. Simulations also showed that boosters for 

nursing home residents can help reduce cases, but the magnitude of their effect depends on 

their effectiveness and staff vaccine coverage. Even with highly effective boosters, cases in 

nursing homes will persist when community transmission is high. This highlights the need for 

continued infection prevention and control strategies and that community transmission remains 

a key driver of cases in nursing homes.

Discussion Points

Dr. Lee observed that clear to many and made more explicit by the modeling is that community 

rates can make a major difference. Community rates of transmission have a direct impact on 

vaccinated and unvaccinated individuals. As community transmission has increased, many 

healthcare facilities have had to reinstate visitor restriction policies, meaning that family 

members cannot visit their loved ones. This is similar for nursing home settings and schools. 

When transmission rates in the community are higher, higher rates of infection are occurring in 

schools as a reflection of the broader community. The model illustrates this well and supports 

efforts to achieve individual- and community-level protection.

Dr. Poehling agreed that the impact of community transmission is very important and 

emphasized that staff vaccination makes a bigger difference than the booster dose among 

residents. 
ACIP Meeting Summary September 22-23, 2021

28

Dr. Chen wondered whether some of this modeling also could be used for understanding 

pediatric populations, such as in schools that remain largely unvaccinated because of younger 

children, or if further modeling exercises already are being conducted internally to help 

understand this in all segments of populations. 

Dr. Slayton emphasized that because nursing home staff vaccination coverage is important and 

influential, given that staff have contacts in the community and can import COVID-19 into 

nursing home facilities. Therefore, increasing staff vaccination coverage is incredibly important. 

Regarding children, CDC is collaborating closely with a consortium of modeling researchers at 

the COVID-19 Scenario Modeling Hub to assess longer term projections that make different 

assumptions about whether vaccines become available for children 5 to 11 years of age and 

what the impact might be on the longer term trajectory. This information can be shared with 

ACIP in a future discussion.

Dr. Kimberlin (AAP Redbook) commented that looking at CDC’s maps by counties reflect the 

areas of the country that are most red in terms of highest rates of transmission in the 

community. Arguably, there really are not efforts within most of those communities to enforce or 

even strongly encourage masking indoors and other efforts that would mitigate transmission 

within the community. That is probably the reason that they are the most red. He requested that 

ACIP consider if/how to apply these modeling results. He did not think many communities within 

the US could be counted on to re-implement masking.

Dr. Zahn (NACCHO) noted that the modeling in nursing homes that Dr. Slayton presented is 

being lived out in communities around the country for local public health and nursing homes. In 

the summertime between when the Delta variant arrived, waning immunity, or some 

combination thereof, it became very clear that even if someone is fully vaccinated, particularly if 

they have a household exposure, their chance of having breakthrough infection is not trivial. 

That becomes a difficult calculation for staff, particularly in SNFs where the risk of introducing 

the virus there is so great. The prevailing thought seems to be that if someone is vaccinated 

they are immune and if they have a community exposure, it is okay to continue to work. Any 

measures to assure immunity as optimized in that staff population need to be considered.

Dr. Maldonado (AAP) reinforced what was said about future modeling, particularly in terms of 

the pediatric population and given what is occurring with return to school and some of the 

restrictions being placed on masks in some of these populations. It is important to make a case 

for or against the risks and benefits of vaccination of not only children 5 to 11 years of age, but 

also for children under 5 years of age for whom there already has been a lot of undercurrent in 

the lay press and across social media around the necessity or not of vaccinating that population.

It is important to have all of those data available when and if ACIP is able to consider the 

pediatric population and transmission, especially within the school setting and given the high 

background transmission rates that can occur within some of the high-risk communities where 

equity may be of particular concern.

Dr. Duchin (NACCHO) agreed with the conclusion that even with highly effective boosters, 

continued infection prevention and control strategies will be needed. He asked whether 

consideration was given to assessing testing strategies and what the impact of frequent 

screening with rapid antigen testing would be on nursing home staff in terms of the incidence of 

COVID-19 among residents.
ACIP Meeting Summary September 22-23, 2021

29

Dr. Slayton indicated that they previously considered questions about frequency of testing in 

their Clinical Infectious Disease (CID) paper33 before there were data about what the various VE 

values would be. They did a wide parameter sweet for the three VE types that she described in 

the presentation during this session. They looked at trade-offs with time limits of results and 

sensitivity to try to better understand what that might do to the magnitude of transmission in 

nursing homes. She pointed out that in the presentation during this session, even with very high 

staff vaccination coverage and very high VE against infections for residents after boosting, there 

are still non-zero values. The importations are more frequent when there is more community 

transmission, which highlights the rationale for increasing the frequency of testing in nursing 

homes when there is more transmission in the community in order to identify importations early

and implement additional infection prevention and control measures to mitigate further spread.

Dr. Zimmerman (APTR) asked whether there had been an opportunity to model various facility 

sizes to determine differences in large versus small facilities, given the potential for density and 

effects of infectiousness.

Dr. Slayton indicated that they have not yet explored all of the facility-level heterogeneity, but it 

is an interesting question to explore in future work.

Dr. Foster (APhA) noted that they often hear that some people do not want to get vaccinated 

because of herd immunity, so he wondered whether it would be possible to factor herd immunity 

into these types of models.

Dr. Slayton said she thought that that there would be a way to estimate what the critical 

vaccination threshold might be based upon what the reproductive number is, but there are also 

important issues with the emergence of novel variants for which there may be a different level of 

cross-protection for persons who either were vaccinated or had an infection with a previous 

variant. There also are issues with the time horizon and questions about waning immunity from 

either natural infection or vaccination that ought to be incorporated. For an infectious disease 

with an R naught 6 or higher, which was the estimate for Delta, it is a very high threshold. It is

even higher perhaps in terms of heterogeneity.

Dr. Duchin (NACCHO) emphasized the importance of the need to have layered prevention 

measures with vaccination, infection control strategies, and testing. However, one very 

important strategy that had not been discussed was ventilation and improving indoor air quality. 

He wondered whether Dr. Slayton’s team considered this. While he knew that there had been 

some modeling around schools and ventilation, based on what is known about the quality indoor 

of air in long-term care facilities, he wondered whether it would be possible to understand what 

type of benefit might be received if 4 to 6 air exchanges per hour could be achieved in addition 

to the other measures.

Dr. Slayton indicated that indoor air quality was not explicitly included in the modeling she 

presented during this session because in nursing home with the level of mixing that would be 

expected (e.g., resident meals, activities, shared rooms, et cetera), this was not explicitly 

evaluated. However, it is an interesting and perhaps future direction.

33 https://academic.oup.com/cid/article/73/3/e792/6132104
ACIP Meeting Summary September 22-23, 2021

30

Dr. Lee asked at what point in the pandemic and in the overall vaccination program for the US, 

recognizing that there is importation globally, when it might be appropriate to consider modeling 

to understand the impact of a booster vaccine on decreasing transmission in addition to 

decreasing the risk of severe disease. She recognized that right now, the greatest opportunity 

continues to be in insuring that the unvaccinated population is vaccinated. She also took the 

opportunity to ask their industry colleagues about continued innovation in this space. While she 

anticipates that boosters will be inevitable, the ability to achieve sterilizing immunity perhaps 

would be a worthy goal to achieve in order to be able to also address this question in the longerterm.

Dr. Slayton said that by looking at the outcomes of symptomatic COVID-19 cases in total 

infection was one way they were hoping to provide ACIP with some data to help think through 

what is occurring with transmission versus disease in the nursing home population. Additionally, 

if there is a recommendation for booster doses, one could adopt that in some larger scale 

population models to look at what the impact might be population-wide. If the booster doses will 

be primarily in older adults, they tend to have less contact than other age groups. Depending on 

where the US is in the pandemic, her best hypothesis is that the magnitude of that effect may be 

small to moderate. Additionally, it would be a worthwhile endeavor to think about multi-year time 

horizons in the model to assess where COVID-19 ends up in the longer-term. Doing that 

accurately with a novel pathogen that is rapidly changing, such as seen with the novel variants, 

is a difficult endeavor. They do continue to work on this along with their colleagues in academia 

and industry to help move this work forward.

Early Safety Monitoring for Third Doses of mRNA Vaccines

Dr. Anne Hause (CDC/NCEZID) presented safety data on reports of additional COVID-19 

vaccine doses to the Vaccine Adverse Event Reporting System (VAERS) and v-safeSM. COVID19 vaccines are being administered under the most intensive vaccine safety monitoring effort in 

US history. CDC is monitoring the safety of these vaccines through 4 complementary systems: 

v-safeSM, VAERS, the Vaccine Safety Datalink (VSD), and the Clinical Immunization Safety 

Assessment (CISA). There are also additional systems in place managed by government

partners.34 During this session, Dr. Hause focused on data from v-safeSM and VAERS.

VAERS serves as an early warning system for vaccine safety. It is co-managed by CDC and 

FDA. Anyone can submit a VAERS report regardless of the possibility of the vaccine causing 

the event or the critical seriousness of the event. The key strengths of VAERS include rapid 

detection of safety issues and detection of rare AEs. Limitations of VAERS include inconsistent 

quality and completeness of information, reporting biases, and that VAERS cannot determine 

causality of AEs. As of September 17, 2021, there were 2563 reports to VAERS following Dose 

3 of mRNA COVID-19 vaccine. The median age was 64 years and 61% of reports were from 

women. Race or ethnicity was unknown or incomplete for 49% of reports and 39% were from 

person who identified as White Non-Hispanic. Of the 2563 VAERS reports following Dose 3 of 

mRNA COVID-19 vaccination, 95% were non-serious. This was regardless of the vaccine 

manufacturer and is similar to what has been observed for COVID-19 vaccines overall and other 

vaccines in general.

34 Full list of U.S. COVID-19 vaccine safety monitoring systems: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety.html
ACIP Meeting Summary September 22-23, 2021

31

The most common AEs reported to VAERS following Dose 3 of mRNA COVID-19 vaccination 

was extra dose administered. This was true for both serious and non-serious reports. Per 

federal law, serious reports include hospitalization, prolongation of existing hospitalization, lifethreatening condition, permanent disability, congenital deformity or birth defect, or death. No 

reports of myocarditis in persons less than 65 years of age were identified. There were 18 

reports of deaths to VAERS following Dose 3 of mRNA COVID-19 vaccination. The median age 

was 76 years. Median elapsed from Dose 3 to death was 1 day. A CDC physician reviewed the 

available documentation, including death certificates, to determine a preliminary impression of 

cause of death (COD). Most preliminary impressions of COD were cardiac or respiratory arrest.

It was not possible to determine COD for 4 reports due to insufficient data.

In terms of v-safeSM data, v-safeSM is a voluntary, smartphone-based safety surveillance system

that allows existing participants to report receiving an additional dose of COVID-19 vaccine and 

new participants to enter information about all doses of COVID-19 vaccine received. The vsafeSM health surveys are sent during the week following each dose of vaccine and include 

questions about local injection site and systemic reactions and health impact (e.g., inability to 

perform normal daily activities, missed school or work, or receipt of medical care). Surveys are 

sent weekly through 6 weeks after vaccination and at 3, 6, and 12 months after vaccination. As 

of September 19, 2021, 21,935 v-safeSM participants had reported an additional dose of COVID19 vaccine. Of these participants, 63% were female. Approximately one-third were 18 to 49 

years of age, 50 to 64 years, and 65 to 74 years. Almost 10% were 85 years or older. Almost 

88% of participants identified as non-Hispanic and 82% identified as White.

Regarding the patterns of vaccination for v-safeSM participants who reported an additional dose, 

98% of participants reported a third dose from the same manufacturer as their primary mRNA 

vaccine series. Among the most frequently reported reactions at least once during Days 0-7 

after Dose 3 of Moderna or Pfizer-BioNTech were vaccine, pain, fatigue, myalgia, and

headaches for both vaccines. In terms of reactions and health impact events reported at least 

once during Days 0-7 after Pfizer-BioNTech vaccination by dose, the odds of reporting an event 

following Dose 2 and 4 were compared using a multivariable generalized estimating equation

(GEE) model that accounted for the correlation between participants and adjusted for 

demographic variables. p-values less than 0.05 were considered to be statistically significant. 

Injection site reactions, systemic reaction, and health impacts including inability to perform daily 

activities and inability to work were all less frequently reported following Dose 3 than Dose 2.

While these differences were statistically significant, the magnitude is small. Regarding 

reactions and health impact events reported at least once during Days 0-7 after Moderna 

vaccination by dose, like Pfizer-BioNTech injection site reactions, systemic reactions, and health 

impacts including inability to perform daily activities and inability to work were all less frequent 

following Dose 3 than Dose 2.

These data are subject to a number of limitations. First, both VAERS and v-safeSM are voluntary 

systems and are likely not representative of the vaccinated US population. Second, during the 

study period, additional dose recommendations were limited to immunocompromised persons

who completed a primary series of mRNA COVID-19 vaccine. However, v-safeSM does not 

include specific information about immune status. Additional dose recipients likely included 

immunocompromised and non-immunocompromised persons. Immunocompromised persons

might have different reactogenicity than immunocompetent persons. Third, insufficient data

were available to determine patterns of AEs after receipt of additional doses from a

manufacturer different from the primary series. Insufficient data also limited the ability to identify 

rare AEs. Finally, complete medical review of deaths following vaccination reported VAERS is 
ACIP Meeting Summary September 22-23, 2021

32

dependent on the availability of medical records, death certificates, and autopsy reports that 

may be delayed or not available.

To summarize, no unexpected patterns of AEs were observed. However, the data are limited at 

this point to identify rare AEs. Nearly all (95%) of reports to VAERS were non-serious. Most vsafeSM participants reported a primary mRNA vaccine series followed by Dose 3 from the same 

manufacturer. Similar to the Pfizer-BioNTech clinical trial data, local and systemic reactions

following Dose 3 were comparable to those following Dose 2. In terms of next steps, VAERS 

and v-safeSM will continue to monitor the safety of additional doses of COVID-19 vaccination.

Additionally, the VSD will incorporate near real-time sequential monitoring. CISA will be

available to consult on clinically complex AEs. ACIP will be updated as additional data become 

available.

Discussion Points

Ms. McNally requested additional information on how the safety monitoring systems would 

capture information regarding mixing of vaccines. She also requested that Dr. Fink comment on 

how the FDA EUA Fact Sheet would address mixing of vaccines if, in fact, this were to be 

permitted.

Dr. Hause indicated that participants can enter information in v-safeSM about which doses they 

have received, so there is information about all doses a person might include. That opportunity 

also is available in VAERS, though sometimes the data are incomplete.

Dr. Shimabukuro added that VSD is an EHR system that has its own immunization registry, so 

those data are captured and it is possible to identify product-specific doses administered 

information.

Dr. Fink (FDA) said he would anticipate that the EUA Fact Sheet would not that data are not 

available to inform the safety or effectiveness of the interchangeability of vaccines.

Dr. Lee highlighted that heterologous boosting is clearly an area of interest, for which they 

learned earlier in the day that those data are on the way.

Dr. Poehling asked whether any cases of hospitalizations or myocarditis were identified in the vsafeSM system among the 21,935 participants.

Dr. Hause indicated that 11 hospitalizations were reported. They do not have the capability to 

comment on the reasons for hospitalizations, given that v-safeSM does not collect information on 

hospitalizations or myocarditis. This system collects reactogenicity data, although some data 

are available in free text form about additional symptoms. In addition, v-safeSM participants who 

indicate hospitalization would receive active follow-up and be encouraged to complete a VAERS 

report with CDC staff, which can be done over the phone.

Dr. Shimabukuro added that in terms of the myocarditis reports to VAERS, there was one 

preliminary report. They are in the process of obtaining follow-up information, reviewing, and 

adjudicating this case. This case occurred in a male 73 years of age who experienced symptom 

onset 22 days after vaccination. Based on the preliminary report, that seems consistent with 

myocarditis. While they have to confirm this, this is not typical for what would be considered 

vaccine-associated myocarditis. This individual falls out of the age range for what is considered 

the age groups of risk. Also, the symptom onset is quite far out compared to most of these 
ACIP Meeting Summary September 22-23, 2021

33

vaccine-associated myocarditis cases. It is outside of the Day 0-7 risk interval and is even 

outside of the Day 0-21 conservative intervals that is used in other monitoring. Therefore, there 

is no indication that this would be a vaccine-associated myocarditis case if it turns out to be a 

confirmed case.

Vaccine Safety Technical Work Group (VaST WG) Assessment of 3rd Dose Safety Data

Dr. Keipp Talbot (VaST Chair) reminded everyone of the objectives of the COVID-19 VaST 

WG are to: 1) review, evaluate, and interpret post-authorization and approval of COVID-19 

vaccine safety data; 2) serve as the central hub for technical subject matter expertise from 

federal agencies conducting post-authorization and post-approval safety monitoring; 3) advise 

on analyses, interpretation, and data presentation; and 4) provide updates to the ACIP COVID19 Vaccines WG and to the ACIP on COVID-19 vaccine safety. VaST has convened 35 

independent meetings to review the vaccine safety data, almost all of which have occurred 

under the purview of Dr. Grace Lee. VaST also has had 8 joint meetings with the COVID-19 

Vaccines WG to review a variety of topics.

VaST continues to review data on myocarditis, Guillain-Barre Syndrome (GBS), anaphylaxis,

and thrombotic thrombocytopenia syndrome (TTS) following COVID-19 vaccination from 

passive and active US surveillance systems, including VAERS, VSD, CMS, VA, Indian Health 

Services (IHS), and the Department of Defense (DoD). This also includes data from outside the 

US from Israel, Canada, and the World Health Organization (WHO) Global Advisory Committee 

on Vaccine Safety (GACVS). Special evaluations are underway, such as follow-up studies of 

myocarditis cases specifically in VAERS, VSD, and DoD. The focus of this session was on the 

safety data regarding a third dose of COVID-19 vaccination reviewed by VaST. Regarding third 

dose safety data on the Pfizer-BioNTech COVID-19 vaccination, VaST reviewed the data 

presented by Israel to the VRBPAC35 and the US data from v-safeSM. 

In terms of the safety data regarding the third dose of Pfizer-BioNTech COVID-19 vaccination

from Israel, third doses were phased in beginning with persons ≥60 years. Since the end of 

August 2021, everyone 12 years of age and over has been eligible to receive a third dose. As of 

September 13th, approximately 2.8 million third doses had been administered to persons ≥12 

years of age. Most third doses have been administered to persons ≥60 years. Rates of reported

systemic, local, neurologic, allergic, and other reactions were substantially lower after Dose 3 

than after Doses 1 or 2. To date, there have been over 1000 non-serious and 19 serious

adverse events (SAEs). All hospitalized patients and deaths have been or are being 

investigated by a work group. Among the serious cases, 7 were possibly associated with 

vaccination. Data from the Israeli Ministry of Health show the rate of systemic adverse events by 

dose. There have been many fewer reported AEs after the third dose. VaST suspects that much 

of this is due to time of follow-up. More data should be following soon. Looking at Israeli data by 

vaccine dose, age group, and sex, the only observed case of myocarditis following vaccination

after a third dose occurred in a male in his 30s.

Turning to v-safeSM safety data after the third dose of COVID-19 vaccination, third doses were 

recorded by over 24,000 participants as of September 11, 2021. While third doses in the US are 

currently only recommended for persons with an immunocompromising condition, there are no 

data in v-safeSM to support that these 24,000 people were immunocompromised or had 

indicated other underlying conditions. Compared to the second dose, the original analyses 

suggested that there may be more local reactions and less systemic reactions following the third 

35 https://www.fda.gov/media/152205/download
ACIP Meeting Summary September 22-23, 2021

34

dose than after a second dose. However, it now appears based on re-analysis that there are 

fewer local and systemic reactions following the third dose.

To summarize the VaST assessment of the Israeli and v-safeSM safety data after the third dose 

of COVID-19 vaccination, the assessment of the Israeli data is limited by likely under-reporting 

of local, systemic, and SAEs. This is likely due to the very short follow-up period. The few SAEs 

potentially associated with vaccination need further follow-up. VaST noted only a single case of 

myocarditis in a male age 32-34 after the third dose of e Pfizer-BioNTech. Data from v-safeSM

show that systemic reactions following third dose are slightly less than following a second 

assessment. The v-safeSM safety data are limited by lack of data on underlying conditions or 

whether recipients are individuals with immunocompromise. The significance of the v-safeSM

data is unclear, given that local and systemic reactogenicity do not predict more severe AEs.

In terms of next steps, VaST will continue to review safety data regarding third doses as data 

become available. In addition, VaST will continue to collaborate with global vaccine safety 

colleagues and key issues that impact the benefit-risk balance and will continue to provide 

updates to the ACIP COVID-19 Vaccines WG and the ACIP during future meetings.

Discussion Points

Ms. Bahta requested more information about why there was suspected under-reporting of 

serious conditions in the Israeli third dose safety data.

Dr. Talbot indicated that the biggest limitation at this point is time. This program was recently 

begun and is slowly beginning to accumulate data. The second aspect is that many of the 

questions about myocarditis is an event that would occur in younger adults, while the majority of 

people who received the third dose were older. It also is unclear how much reporting there is 

following a third dose, given that this is self-reported information.

Dr. Daley said he was trying to interpret whether the strengths and limitations of the data 

coming out of Israel were more similar to the strengths and limitations of the VAERS data or the 

VSD data. It was not clear to him whether the Israeli system misses hospitalizations postvaccination and/or vaccine doses or if capture of these is likely to be pretty good.

Dr. Shimabukuro said he would have to familiarize himself more with the Israeli data to 

determine whether it is equivalent to an EHR-based system like VSD, but he thinks it has better 

capture of information than a purely passive system like VAERS. It is a smaller country and 

smaller population, so their capture of information may be somewhat better than VAERS.

Dr. Poehling asked whether there has been any observed GBS or anaphylaxis among the 2.8 

million doses that have been administered.

Dr. Talbot indicated that there was 1 GBS followed by Bell’s Palsy.

Dr. Sanchez found the data to be reassuring for those who decided to receive a third dose, but 

wondered whether those who had more severe reactions post-Dose 1 or 2 may not have 

decided to take a third dose. They will have to grapple with this as well if there is a 

recommendation for a booster dose.

Dr. Talbot agreed that it would be beneficial to have data about how many people decided not to 

receive a third dose due to having a reaction after Dose 1 and 2.
ACIP Meeting Summary September 22-23, 2021

35

Ms. Howell (AIM) asked whether there are any data from Israel or the US showing whether 

people who previously had COVID-19 or had a breakthrough infection after being vaccinated 

had increased AEs following a third dose.

Dr. Lee reminded everyone that the Israeli data were presented during the VRBPAC meeting 

the previous Friday and that those slides could be accessed on the FDA website at: 

https://www.fda.gov/media/152205/download

Dr. Talbot indicated that the booster analysis, shown on Slide 21 of the Israeli data that were 

presented to the FDA, excluded people who had been infected previously. While this analysis 

includes data on people 60 years of age and above, it does not include information about AEs.

Dr. Shimabukuro commented on a couple of ongoing studies. There is a fairly large case-control 

study for the basic series looking at prior infection as a risk factor for more severe reactogenicity 

using v-safeSM data that is in progress for which CDC hopes to have preliminary results soon. 

He also is aware of another study on which CDC is consulting that is being conducted 

elsewhere. That does not get at the original question about third dose. It seemed like one would 

have to have a breakthrough case after the second dose and get a third dose to answer that 

question, which may be a rare event.

Dr. Long requested clarity about the time interval between Dose 2 and Dose 3, which seemed 

very relevant if they are trying to assess something like myopericarditis that is happening in 

younger people—especially teenagers because they are going into their second dose with very 

high antibody. That might be the case for the third dose in people who had a reason to have a 

third dose as the primary series and would be much less likely in those who are truly getting a 

booster if it has been 6 plus months.

Dr. Talbot indicated that everyone in the general population in Israel was eligible for an 

additional dose, whether called a booster or a third dose, 5 months after the second dose. She 

did not readily have data on what the average length of time was between Dose 2 and Dose 3.

COVID-19 Work Group Summary

Dr. Sara Oliver (CDC/NCIRD) reminded everyone that as mentioned previously, any policy on 

booster doses will be coordinated with FDA for regulatory allowance and ACIP for

recommendations for use. The COVID-19 WG has reviewed the data and as is the standard 

process, they await FDA action and then ACIP can make recommendations for use. As a 

reminder, the data used to inform recommendations for booster doses of COVID-19 vaccines

presented during this session included safety and immunogenicity for a third dose of BNT162b2, 

immunity and SARS-CoV-2, VE in the US, modeling the potential impact of booster doses in 

nursing home residents, and early safety monitoring for third doses of mRNA vaccines. Dr. 

Oliver provided a brief summary and WG interpretation of these presentations.

To summarize the safety and immunogenicity for a third dose of BNT162b2 from the PfizerBioNTech presentation, the data shown were from 23 individuals from the Phase 1 study who 

were boosted approximately 8 months after the second dose and 312 individuals from the 

Phase 3 study who were boosted around 7 months after the second dose. When the 

immunogenicity data were evaluated 1 month after the booster dose, the GMTs were around 3-

fold higher than 1 month after the second dose. To evaluate the proportion with a seroresponse,
ACIP Meeting Summary September 22-23, 2021

36

99.5% responded after the booster dose compared to 98% after the second dose and 

reactogenicity was similar after the booster dose and after a second dose.

The WG highlighted the number of individuals included in the evaluation for safety and 

immunogenicity from the manufacturer. Overall, the immunogenicity data are reassuring, but 

many unknowns remain. It is unknown what the clinical impact is of lower antibody levels seen

pre-booster. In addition, the antibody kinetics over 1 month post-boost, including the rate of 

waning, is currently unknown. While increasing antibody levels are encouraging, it is unknown

how the boost of antibody seen will directly translate to clinical protection. Although the safety 

data are also reassuring, there is limited size. There were 306 individuals included in the safety 

population. Based on those numbers, it is not possible to determine the risk of rare side effects 

such as myocarditis after a booster dose. Finally, the WG anticipates the ability to review 

additional data from an ongoing trial with around 10,000 individuals in upcoming weeks or 

months.

Moving to the presentation describing immunity and SARS-CoV-2, Dr. Thornburg described that 

the immune response generated by COVID vaccines is broad, including both cellular and 

humoral immune responses. In addition, waning of antibodies likely does not represent the 

entire picture. Memory B cells are maintained out to 6 months after the primary series. In 

addition, the immune response may be impacted by both aging and variants. Finally, Dr. 

Thornburg described data demonstrating that transmission is possible with infections after 

vaccination. However, the WG discussed that it is unknown how booster doses of COVID-19

vaccines may impact transmission.

As Dr. Link-Gelles mentioned in her presentation, current VE studies in the US will provide 

additional context around global VE studies in a subsequent presentation. This presentation

demonstrated significant declines in VE against infection in individuals ≥65 years of age for 

mRNA products in the time since Delta. There were smaller declines in VE against

hospitalizations in individuals ≥65 years of age, but it was more substantial in this age group 

than in younger populations. Among adults less than 65 years of age, vaccines remained 

effective in preventing hospitalization and severe disease. However, the vaccines may be less 

effective in preventing infection or milder asymptomatic illness due to both waning over time and 

the predominance of the Delta variant.

In terms of the modeling results from the impact of booster doses in nursing home residents, the 

results demonstrated that both increasing vaccination coverage of staff and increasing VE in 

residents can impact cases among these LTCF residents. Community transmission levels also 

substantially impact cases in LTCF. The WG discussed that these data demonstrate that 

booster doses are one way to protect the vulnerable LTCF population. However, it is not the 

only way to protect this population. In addition to including booster doses for LTCF residents, 

VE can be improved among LTCF residents by increasing vaccination coverage of LTCF staff. 

Lower rates of community transmission will be important. High rates of community transmission, 

even with additional vaccines delivered, can lead to COVID importation into facilities.

Given that Dr. Talbot summarized the safety data and the VaST perspective, Dr. Oliver did notre-summarize it and did express appreciation for VaST’s thorough review of the safety data.
ACIP Meeting Summary September 22-23, 2021

37

In terms of next steps, in accordance with the standard process, FDA is carefully evaluating the 

data and will issue the regulatory allowance after their review. After FDA regulatory action, ACIP

will have additional discussion around recommendations for use. Dr. Oliver invited ACIP to 

comment on any additional data they may wish to review before discussions around COVID-19 

vaccine policy.

Open Discussion

Dr. Lee emphasized that the data presented were the data available at this point, but the 

COVID-19 Vaccine WG and VaST will continue to review emerging data as they become 

available. She invited ACIP members to provide input on key areas that might impact the 

discussion about the use of boosters in the US populations.

Ms. Bahta said she was grappling with what the goal was in terms of whether it was to just 

prevent disease, which Dr. Long pointed out is not possible. If the goal was to prevent severe 

disease, consideration must be given to how much would be gained by providing booster doses 

to certain individuals and how the benefit would weigh against political issues and ethical issues 

in terms of global partnerships. She also expressed concern that the data are small. Even the 

data for the 65-75 year old group was an N of 12. It was not clear whether this was a time of 

urgency for which they have to make a decision despite insufficient or lack of evidence.

Dr. Poehling reiterated the importance of being very clear about the goal if there is a 

recommendation for a booster. She thought it would be helpful to see the epidemiology on 

breakthrough infections and the anticipated benefits and potential side effects by age, race, and 

ethnicity.

Dr. Chen observed that in discussion COVID-19 booster doses, they seemed to be constrained 

by existing recommendations that seemed to lock a person into whatever primary series of 

vaccine they received. It would be beneficial for a booster dose to be agnostic to the primary 

series, allowing for the ability to administer boosters feasibly and in a way that does not require 

knowledge of the primary series. This would be his preference for the ease of implementation of 

booster doses.

Dr. Kotton agreed with Dr. Chen regarding making a booster as feasible and available as 

possible. Currently, there are a lot of combinations of vaccines being given as far as second or 

third doses depending upon the series. Some flexibility needs to be incorporated, but with an 

appreciation for the law, licensure, approval, EUA, et cetera. Even with a third dose, many 

immunocompromised patients (~3% of the US population) still remain not well-protected against 

COVID-19. The recommendations have been that they should be very carefully following 

infection control measures, so they still are living such that they cannot have life back yet. Better

primary vaccination of the overall population definitely would help curtail the pandemic and 

would better help protect them. Thinking about the nursing home or LTCF model presented, it 

was not clear whether booster doses would help protect this population. She would be optimistic 

that immunocompromised individuals would be better protected if the overall population was 

better protected.

Dr. Sanchez agreed with clearly establishing the goal for the third/booster dose. With a 

respiratory virus, the goal really needs to be prevention of severe infection as defined by 

hospitalization and/or death—not just asymptomatic or mild infection. With hospitalization, it is 

really hospitalization due to COVID—not just those who are hospitalized for other purposes and 

found by screening to be positive upon admission. The safety presented thus far has been 
ACIP Meeting Summary September 22-23, 2021

38

somewhat limited, especially for booster doses. For the Pfizer product, there are no data for 

those less than 18 years of age. He agreed with a recommendation for a third dose for 

immunocompromised individuals. He would argue more for age rather than just risk of 

exposure. In addition, there are differences between the Pfizer and Moderna mRNA, which may 

need to be assessed further for ultimate recommendations. Data are needed on the Janssen 

product. Patients who have received the Janssen product have been left out not only for the 

consideration of boosting, but also the consideration for a third dose for immunocompromised 

persons. Janssen has second dose data now, which ACIP has not yet seen. They do need to 

comment on those who received the Janssen product and the availability of mRNA vaccine.

Dr. Daley expressed appreciation for the line of discussion that vaccination is not going to 

eliminate transmission. He also would add that it is possible that booster doses could decrease 

transmissibility, but that is an unknown and in that case would be the societal benefit of 

someone getting a booster. In terms of the individual risk-benefit calculus, most people probably 

have multiple considerations in terms of making a decision about getting a booster, but are likely 

thinking about their individual risk-benefit. The unknown about transmissibility is difficult to factor 

in there, because they may not directly benefit from that reduction in transmissibility even 

though others in their community may.

Regarding Dr. Sanchez’s earlier comment, Dr. Loehr indicated that a large number of the 

hospitalizations with COVID-19 in his community are incidental findings of people getting 

admitted for something like a knee replacement, but testing positive for COVID upon admission.

He asked the WG whether it would be possible to tease out hospitalizations due to COVID 

versus COVID as an incidental secondary diagnosis, which would help him to make a decision.

Dr. Talbot indicated that the COVID-NET hospitalization network is able to differentiate to some 

degree, but it is not easy to do and incidental cases tend to be the minority of cases. In addition, 

she thought the purpose of vaccinating HCP was not to prevent mild disease but to reduce mild 

disease so that HCP can return to work. There are not enough HCP in some areas to take care 

of unvaccinated, who just keep coming even though many have to be turned away in areas 

where there are not enough beds. When there are beds, there often are not enough staff. The 

idea of vaccinating HCP would be different from vaccines in the general population.

Dr. Duchin (NACCHO) observed that much of the data they saw during this session were 

categorized by age groups, 50-65 and 65 and older, and asked for additional information about 

how confident ACIP feels about where the line is drawn in terms of age and putting that in the

context of the continuum of risk that exists above 50 years of age for instance.

Dr. Bell agreed that it is extremely important to have clarity about the issue of heterologous 

boosting and whether they were considering recommendations directed only toward people who 

received the primary series of the Pfizer vaccine or a much broader population of people with 

other characteristics as candidates. Second, the point about the objectives is pivotal and she 

agreed that the objectives here were about preventing serious illness and death. In that context, 

she reiterated that if they were considering HCP and other occupational groups, they would 

need to be giving some thought to a different objective of preventing absenteeism and 

workforce issues. Third, it is extremely important to keep in mind that ACIP would be making

recommendations for now. Based on the data presented, they were not hearing about major 

gaps in data at the moment. There remain many data gaps and a huge number of moving parts

such that things could change substantively in a relatively short period of time. She emphasized 

that these are interim recommendations and there may be data forthcoming in the near future 

that may change those recommendations.
ACIP Meeting Summary September 22-23, 2021

39

Dr. Long stressed that ACIP had only the Pfizer vaccine data in front of them and it did not 

appear that they would hear any data on mixing and matching vaccine product, meaning the 

possibility that ACIP would recommend being boosted with what was received in the primary 

series. While she did not have a strong opinion about this theoretically, it would leave half of the 

people immunized in this age group being told that they are at risk for waning immunity and 

hospitalization but unable to receive a booster. That is a public health panic they would like to 

avoid. ACIP needs data for the Janssen recipients because it is not clear whether they would 

need 2 doses if they received a completely different product. She wondered how long it would 

be before ACIP could expect to see data from NIH and before FDA would see Moderna’s 

information. Given that the dose for the Moderna booster may be different, that will result in 

further complications in terms of mixing and matching. Therefore, ACIP probably should make a 

decision about mixing and matching before making a recommendation about Pfizer at all. She 

asked whether anyone over 65 years of age had been on a ventilator and died because of a 

breakthrough case of COVID, given that there are many reasons to hospitalize people at this 

age.

Dr. Link-Gelles indicated that there have been cases of fully vaccinated individuals 65 years of 

age and older who had a breakthrough case and died. A couple of VE studies are underway, 

but the numbers are small so it will take a while to get actual VE estimates.

Dr. Sanchez raised the issue of whether individuals who have had symptomatic disease should 

receive a third dose.

Dr. Lee agreed that goals of the vaccination program and being very clear about it would be 

very important in helping to explain any ACIP recommendations. She believes the goals of the 

vaccination program will be dynamic over time depending on the status of the vaccination 

program. A substantial number of individuals are still unvaccinated, but the hope is to be in a 

different place in a few months in which case the goals may change or shift accordingly. 

Second, while ACIP has considered the product-by-product benefit-risk assessment and given 

dynamics of COVID in the moment the data are being reviewed, at some point ACIP will have to 

shift to a model like that for influenza to provide overarching recommendations that make sense 

for the overall population from clinical, population, and public health perspective and then 

explain any nuances under the overarching recommendations. Third, she feels that some of the 

struggle she has in terms of a path forward is the balance of ensuring the safety of vaccines in 

the population, ensuring access to vaccines for individuals, and addressing and maintaining a

focus on equity. Specific to equity particular to the Janssen population, they also have to make 

sure that what they do makes good clinical sense for individuals and that they are not looking at 

everything in silos.

Dr. Brooks suggested that part of the deliberations should focus on what would cause the ACIP 

to adjust or revise any recommendations made during the next day of the meeting, given that 

these would be interim recommendations. They should go on record to state specifically what 

those parameters would be.

Circling back to the question about hospitalizations and whether they were attributable to 

COVID-19 or COVID-19 was incidentally diagnosed, Dr. Link-Gelles differentiated between a 

couple of the platforms. Platforms that have individual-level data have individual clinical 

information on cases such that they can include CLI as part of their case definition, so it is pretty 

reasonable to assume that those cases are actually hospitalizations associated with a COVID 

illness. Surveillance platforms generally do not have that ability and usually require a SARSCoV-2 test within a certain timeframe of hospitalization.
ACIP Meeting Summary September 22-23, 2021

40

Dr. Beigel (NIH) indicated that the full dataset for Pfizer, Moderna, and Janssen boosts would 

not be available until later in the fall. That will include Day 15 and Day 29 immunogenicity and T 

cell work that is planned, though he did not have a timeline on that. The enrollment was for 

Moderna boost first, then Janssen, and then Pfizer. The Pfizer data are probably the last that 

will be available to them. It would be helpful to discuss what datasets would be beneficial, and 

perhaps it would not be necessary to wait for the full dataset. Discussion might be easier offline 

or in the WG in terms of timelines, data within those that might be informative to ACIP, and how 

to present those data.

Dr. Weiser (IHS) asked whether there is a way to obtain more data that would look at other risk 

factors in addition to age for AI/AN populations, such as race for teasing out the interplay 

between race and comorbid conditions.

Dr. Cohn reminded everyone that if the FDA issued an EUA, ACIP policy would have to align 

with the language of the conditions of use. The data presented by Pfizer earlier in the day and 

the data that the FDA reviewed were all based on the Pfizer primary series with a Pfizer boost. 

She emphasized the importance of the issues pertaining to equity and not leaving groups of 

people behind, but this is a rapidly moving issue and data on the other vaccine series are 

rapidly behind Pfizer. FDA will be deliberating as fast as they can, but people do need to 

consider all of these as interim policies that will be adapted and responded to as epidemiologic, 

safety, and effectiveness data emerge on these vaccines. ACIP is fortunate to be able to return 

anytime there are new data to support changing policy.

Dr. Long requested that Dr. Lee ask Dr. Fink whether there is any timeline for Moderna filing for 

EUA for a booster. She also expressed an interest in seeing an estimate of what the downside 

would be of not recommending a booster for those ≥65 years of age at this time and instead 

waiting if they thought “rapidly emerging” meant that there would be a Moderna authorization

within a month.

Regarding the question about Moderna filing for EUA of a booster dose, Dr. Fink (FDA) said he 

thought that Moderna stated publicly that they filed a submission. FDA is working as rapidly as 

possible to review that submission. In terms of the question pertaining to heterologous boosting, 

he reiterated that there are no data from the FDA’s perspective to inform interchangeability of a 

booster dose of one vaccine with a primary series of another vaccine. However, he appreciated 

the concerns with regard to flexibility and timing of availability of other authorized vaccines for a 

booster dose. In order to ensure that he could be as accurate as possible in addressing these 

concerns, he indicated that he would need to seek input from FDA leadership as to the legal 

considerations for that question for which he hoped to provide a response the next day.

Ms. McNally requested clarification on whether Dr. Fink was speaking about the Public 

Readiness and Emergency Preparedness Act (PREP Act) immunity issue, and on whether the 

Countermeasures Injury Compensation Program (CICP) program also was considering the 

issue of heterologous boosting.

Dr. Fink (FDA) clarified that he was speaking specifically of the FDA legal interpretation of the 

condition of an EUA should the Pfizer vaccine be authorized for use of a booster dose following 

a Pfizer vaccine primary series. There are other considerations such as the PREP Act that also 

would need to be addressed.
ACIP Meeting Summary September 22-23, 2021

41

Dr. Rubin (HRSA) added that the PREP Act is very specific in the declaration in terms of 

countermeasures for COVID-19 vaccines that have FDA EUA or Biologics License Application 

(BLA) approval. CDC/ACIP recommendations do not affect what is covered under the CICP.

Dr. Loehr asked what the implications would be if the ACIP decided to table the vote for a third 

dose for a month or two.

Ms. Howell (AIM) commented on the implementation of third doses, especially in terms of going 

to a number of LTCFs across the US. The vast majority of North Dakota LTCFs administered 

Moderna and Pfizer products, so it was not clear whether returning with different brands would 

be feasible. Similar to the recommendation for the additional dose for immunocompromised 

individuals, she wondered whether either brand could be used for a third dose in a LTCF. She 

also wondered whether individuals ≥65 years of age could be included with 

immunocompromised individuals as needing an additional dose, which would give individuals 

who received either Moderna or Pfizer access to third doses. North Dakota also has a lot of 

people who already had COVID, so more data would be helpful on how many doses people who 

have had COVID need to reduce their chance of reinfection.

Dr. Oliver indicated that after FDA had taken a regulatory action on this, they would be able to 

have an open discussion using the EtR Framework. She reminded everyone that the EtR 

Framework would include not only an assessment of the public health problem regarding 

whether booster doses are needed, but also the benefits and harms, values and acceptability, 

feasibility, resource use, and equity.

Pregnancy: Safety Monitoring in v-safeSM

Dr. Christine Olson (CDC/NCEZID) presented results from CDC’s results from the v-safeSM

COVID-19 vaccine pregnancy registry, one of the vaccine safety monitoring systems for COVID19 vaccination during pregnancy. To provide an overview of the enrollment process, people who 

use the v-safeSM after vaccination health checker indicate whether they are pregnant at the time

they received a vaccine or if they become pregnant after vaccination at later check-in points. 

They are screened for eligibility for the pregnancy registry based on whether they were either 

pregnant at the time of vaccination or were vaccinated in the pre-conceptual period, defined as 

the 30 days before the first day of the last menstrual period before the pregnancy. Eligible 

individuals are then consented for pregnancy registry enrollment and are interviewed at 

designated time periods. The active follow-up for pregnancy registry participants includes

interviews during each trimester after being enrolled, during the postpartum period, and during 

early infancy. Not all participants will be interviewed during all trimesters of pregnancy, but they 

may enter the registry at any point in the continuum if they meet eligibility criteria.

The current distribution of the 5096 enrolled pregnancy registry participants by vaccine 

manufacturer as of September 13, 2021 included 2584 (5.7%) Pfizer-BioNTech, 2236 (43.9%)

Moderna, and 276 (5.4%) recipients. In terms of timing of the first COVID-19 vaccination during 

periconception or pregnancy among v-safeSM pregnancy registry participants, there is 

distribution of vaccination across all pregnancy time periods. About 5% of participants were 

vaccinated in the peri-conceptual period, 28% in the first trimester, about 42% in the second 

trimester, and about 25% in the third trimesters. By the end of September 2021, about 75% of 

the first approximately 1400 women who received vaccination in the first trimester or periconception women enrolled in the pregnancy registry will have reached their estimated dates of 

delivery. These participants will have postpartum follow-up interviews typically conducted 

between 4 and 8 weeks after delivery and an infant follow-up after infants have reached 3 
ACIP Meeting Summary September 22-23, 2021

42

months of age. Therefore, completed infant follow-up interviews for the majority of these 

pregnancies are not expected until November 2021 through January 2022.

In terms of the characteristics of the enrolled pregnancy registry participants, the demographics

largely reflect the people who were initially prioritized for vaccination when vaccines first 

became available and those who chose to enroll in v-safeSM following vaccination. Most 

participants were 25 to 35 years of age, with a very low proportion under 25 years of age. For 

reference, over 20% of live births in the US are to women under 25 years of age. Participants 

were predominantly non-Hispanic white. Over time, those enrolling in v-safeSM have become 

more racially and ethnically diverse. The v-safeSM pregnancy registry participants’ occupations 

were derived from the question asking about vaccination priority group showed that the majority 

of those who received the mRNA vaccines identified as HCP. That was the least represented 

group among those who received J&J vaccine. There are several reasons likely contributing to 

this, including that much of the initial vaccination of HCP occurred before the J&J vaccine 

received its EUA and that the J&J vaccine with less stringent storage requirements made it 

more likely to be used outside of large healthcare settings.

A recent v-safeSM publication36 focused on an analysis of early pregnancy losses. The objective 

in this analysis was to assess among the registry participants the cumulative risk of 

spontaneous abortion (SAB) for pregnancy loss occurring at less than 20 weeks gestation. The 

analysis included 2456 pregnant people enrolled in the v-safeSM registry who had received at 

least 1 dose of an mRNA COVID-19 vaccine peri-conceptually or during pregnancy prior to 20 

weeks of gestation who had not had a pregnancy loss before 6 weeks of gestation. Lifetable 

methods were used to examine the cumulative SAB risk by gestational week in this cohort.

Recipients of the J&J vaccine were not included in this analysis because as mentioned earlier, 

only about 5% of registered participants received that vaccine. Results showed an unadjusted

cumulative risk of SAB after mRNA COVID-19 vaccination of 14.1%. Because most of the 

registry participants are over 30 years of age and therefore slightly older than the general US

pregnant population, the investigators age standardized using a reference population study on 

the risks of SAB according to maternal age group and found a slightly lower risk of SAB of 

12.8%. As expected, the cumulative risk of SAB increased with maternal age. These risk 

estimates fall within published baseline estimates of SAB of 11% to 22%. This provides 

additional evidence that mRNA COVID-19 vaccines in pregnancy are not associated with SABs.

A sensitivity analysis was conducted of the 65 participants who met inclusion criteria for this 

study, but who could not be reached for the second trimester follow-up and thus for whom it was 

not possible to ascertain pregnancy status as of 20 weeks gestation. Under the extreme 

assumption that all 65 of these individuals have had an SAB, the cumulative risk of SAB was 

18.8% before and 18.5% after age standardization. In terms of the weekly cumulative risk for 2 

published historical cohorts37 representing the lower and upper ranges of SAB risk, the results 

for both the primary analysis and the sensitivity analysis fell within the bounds of these 2 

historical cohorts representing the expected risk range.

36 Zauche et al. Receipt of mRNA Covid-19 Vaccines and Risk of Spontaneous Abortion. N Engl J Med. 2021 Sep 8. doi: 

10.1056/NEJMc2113891

37 Mukherjee et al., 2013 and Goldhaber and Fireman, 1991
ACIP Meeting Summary September 22-23, 2021

43

Regarding v-safeSM pregnancy registry infant outcomes at birth for which CDC has preliminary 

information based on participant self-reported data and focusing on results for 1613

pregnancies, this analysis began with the 5096 enrolled participants and was limited to those 

who had an estimated date of delivery (EDD) before May 15, 2021. This was done to allow 

enough time for postpartum interviews to be conducted in the typical timeframe after delivery 

and data to be cleaned, reviewed, and analyzed. Among this group, approximately 500 were still 

pending follow-up and 63 were determined to be lost to follow-up. The resulting 1613 

pregnancies produced 1634 live-born infants, 32 of whom were the results of twin gestations. Of 

this participant cohort, 70% received COVID-19 vaccine in the third trimester and 30% in the 

second trimester. Information is included about the participants in the registry who received 

vaccine earlier than the second trimester of pregnancy, which currently includes 1428

participants. These pregnancies and follow-up are ongoing and therefore data are incomplete at 

this time. However, the outcomes of these pregnancies will be included in future reports. Infant 

outcomes of interest among the 1634 live-birth infants included preterm birth, small-forgestational-age, admission to the Neonatal Intensive Care Unit (NICU) after birth, and neonatal 

or infant death. The proportions of these outcomes in this birth cohort are consistent with or 

below the reference background rates.

To provide some context now on registry participant self-reported birth defects, most birth 

defects arise in the first trimester. However, there are only sufficient data at this time to report

on birth defects among participants who were vaccinated in the second and third trimesters. As 

shown earlier, pregnancies among participants vaccinated in the first trimester are either still 

ongoing or have not yet had ample time to schedule follow-up interviews and data review. 

These data will be presented in the future as they become available. Data in the registry are 

self-reported by participants during the postpartum interview. Participants responded to the 

question, “Was your baby diagnosed with a birth defect?” Reported birth defects were reviewed 

by birth defect experts to assess whether they met inclusion criteria and were then categorized. 

Birth defects were defined as a structural abnormality, chromosomal anomaly, or genetics

syndrome. The types of birth defects reported following vaccination in the second and third 

trimesters are consistent with what would be expected based on population-based birth defect

surveillance systems. For example, heart defects are the most common type of birth defect. 

Among those, septal defects predominate. No unusual birth defect types of clusters of birth 

defects have been noted. Because pregnancies where vaccination was received in the first 

trimester were not included in this current cohort and because the reported number of infants 

with birth defects was small, these current data are not sufficient to assess an association 

between birth defects and COVID-19 vaccination. However, these reported birth defects by 

participants do indicate that the registry is identifying this important outcome and the distinct 

types, which is needed to address the larger question.

In terms of concluding thoughts regarding the information reviewed, there are accumulating data 

from the pregnancy registry on the safety of COVID-19 vaccination during pregnancy.

Specifically, the currently available registry data have been reviewed and no evidence has been 

found of any increases in spontaneous abortion rates or of any disproportionate negative infant 

birth outcomes. CDC will continue to closely monitor the safety of COVID-19 vaccination during 

pregnancy and will provide updates as more data become available. The pregnancy registry is 

continuing to enroll participants, with the goal of enrolling up to 20,000 participants for each 

vaccine type.
ACIP Meeting Summary September 22-23, 2021

44

Discussion Points

Dr. Daley observed that the pandemic has shown that what was thought to be impossible or 

hard to do is really possible. This is an example in which a surveillance system has been able to 

recruit and enroll women and then follow them over time. It is known that there are a number of 

difficulties of enrolling pregnant women in initial Phase 3 clinical trials, but it is very fortunate 

and important to have these data. He found the Zauche et al. data on Slide 14 to be very 

reassuring in the sense that the sensitivity analysis is the most conservative and even that is 

below Muckherjee et al. He wondered whether it would be possible to put the Goldhaber and 

Fireman data into some context in terms of whether they used very different methods or that 

SABs have increased in the last 30 years, which is possible given how demographics have 

changed and other things.

Dr. Olson indicated that interestingly, the data behind the historical reports and reports over time 

of SABs vary quite a bit—probably more than one might have expected before diving into the 

literature. There is considerable variability in the populations reported upon and the 

ascertainment of diagnosis of pregnancies and how losses are identified and confirmed. While it 

is difficult to compare studies directly to each other, they felt it was important to look at the 

range of SAB reports, evaluate the methodologies, and select the ones that seemed the most 

appropriate and similar to what they were trying to do. However, there still are variations among 

them. They were fortunate to be able to obtain the input of one of the leading subject matter 

experts (SMEs) in this area who contributed greatly to the methodology and the literature on this 

assessment.

Dr. Goldman (ACP) noted that a lot of times vaccine-hesitant male patients are concerned about 

male fertility and there is a lot of disinformation. He wondered whether there are data along that 

line or if this could be assessed in terms of tackling the social media and disinformation that is 

occurring regarding this issue.

Dr. Olson acknowledged the concern that has been expressed about fertility and that has taken 

off within social media. This study did not assess vaccine-hesitant male patients because all of 

the participants are already pregnant. They have assessed some preliminary data reported into 

v-safeSM at the 3- and 6-month check-in points in the symptom tracker. For individuals who 

answered the question at the 42-day mark and indicated that they were not pregnant, over 

20,000 participants in the v-safeSM symptom tracker have reported positive pregnancy tests 

beyond the point at which this question is asked. They do not have any information that she is 

aware of about males and fertility issues.

Given that more than 80% of participants were HCP and do not reflect the general population, 

Dr. Cineas asked whether any subgroup analyses were performed in the non-HCP participants.

Dr. Olson indicated that this has not been done to date. As they are continuing to enroll, the 

proportion of HCP will decrease. They are aware that the study population demographics are in 

the process of shifting because of the time course. They are following the pregnancies as they 

move along, with the initial group being followed being comprised of those who received vaccine 

when it was first available and prioritized for HCP. Additional steps are being taken to ensure 

that they have a better balanced study population in addition to the fact that the population pool 

from which they are drawing for interviews has changed over time.
ACIP Meeting Summary September 22-23, 2021

45

Pregnancy: Safety Monitoring in the Vaccine Safety Data Link (VSD)

Dr. Elyse Kharbanda (HealthPartners Institute) presented VSD data on the safety of COVID19 vaccines before and during pregnancy, spontaneous abortion following COVID-19 

vaccination, and stillbirth surveillance. As a reminder, the VSD is comprised of 9 integrated 

health systems working in collaboration with CDC. Of these health systems, 8 are data

contributing sites. These sites create standardized files using data from EMR, claims, and 

administrative databases with weekly updates. Sites also create more comprehensive data files, 

which include birth records. These are updated on an annual basis.

Before presenting the data, Dr. Kharbanda described the algorithms that are the critical 

underpinnings of this work. Previously, the VSD developed and validated the pregnancy 

episode algorithm (PEA). This algorithm is applied to the VSD annual data files and is used to 

identify completed pregnancies. The PEA is the algorithm that was used in prior VSD studies of 

maternal Tdap and maternal influenza vaccine safety. Recently, an enhanced pregnancy 

algorithm was developed and validated known as the dynamic pregnancy algorithm (DPA). The 

DPA incorporates data from the standardized VSD files with weekly updates and is used for 

identifying ongoing pregnancies.

The DPA has made work on the safety of COVID-19 vaccine and pregnancy possible. Using the 

DPA, it is now possible to track receipt of COVID-19 vaccines before and during pregnancy in 

the VSD in near real-time. Data on COVID-19 vaccines administered between December 14, 

2020 and July 31, 2021 showed that there were 122,998 pregnancies in the VSD. There were 

10,178 pregnancies in women who received ≥1 COVID-19 vaccine dose prior to pregnancy and 

6,792 pregnancies with 2 vaccine doses prior to pregnancy. As of July 31, 2021, there have 

been 31,080 pregnancies with ≥1 vaccine during pregnancy and 23,310 pregnancies with 2 

vaccine doses during pregnancy.

Turning to current data from a recently published study on SABs following COVID-19 

vaccination during pregnancy38, SABs and ongoing pregnancy were identified for 6-19 weeks

gestation. SABs were assigned to a single 4-week surveillance period. Ongoing pregnancies,

including pregnancy time before SAB, was assigned to one or more surveillance periods. For 

these SAB cases and ongoing pregnancy period controls, GEE was used to calculate the odds 

of exposure to a COVID-19 vaccine in the 28 days prior to the SAB compared to the odds of 

exposure to a COVID-19 vaccine in the 20 days prior to an index date in the ongoing 

pregnancies, while adjusting for gestational age groups, maternal age groups, receipt of 

prenatal care, race, ethnicity, and VSD site.

For COVID-19 vaccines received before 20 weeks, data were available for 105,446 unique 

pregnancies included in the cohort from December 15, 2020 to June, 28, 2021 and were 

stratified by ongoing pregnancy versus SABs. Most vaccines received were mRNA. Ongoing 

pregnancies could contribute data to more than one surveillance period so during that same 

timeframe, there were 264,104 pregnancy-periods. Receipt of COVID-19 vaccines in the prior 

28 days was stratified by ongoing pregnancies versus SABs. Across all pregnancy-periods and 

strata, 8.0% of ongoing pregnancies and 8.6% of spontaneous abortions received a COVID-19 

vaccine in the prior 28 days. These same comparisons were assessed by gestational age 

groups, maternal age groups, race/ethnicity, number of antenatal, and by surveillance period. 

Most vaccinations occurred between March and May. For the full population, the adjusted odds 

38 Kharbanda et al. Spontaneous Abortion Following COVID-19 Vaccination During Pregnancy. JAMA. 2021 Sep 8. doi: 

10.1001/jama.2021.15494.
ACIP Meeting Summary September 22-23, 2021

46

of COVID-19 vaccination in the 20 days prior to SABs as compared to ongoing pregnancy

controls was 1.02 with a 95% confidence interval of 0.96 to 1.08. Odds ratios varied slightly 

when stratified by gestational age. There was no difference in the odds ratios when stratified by 

vaccine manufacturer. Adjusted odds ratios were not calculated for the Jansen vaccine due to 

the small number of exposures.

A few limitations should be noted. First, SAB cases were not chart-confirmed and dating may be 

inaccurate early in pregnancy. Second, it was not possible to adjust for some potential 

confounders, including prior pregnancy history. Nevertheless, in summary the investigators 

found that among women with SABs, the adjusted odds of a COVID-19 vaccine exposure were 

not increased in the prior 28 days as compared to women with ongoing pregnancies. Next, they 

are planning to conduct an individually matched case-control study with all SAB cases chartconfirmed. 

In terms of updates on monthly surveillance for stillbirths following COVID-19 vaccination, 

potential stillbirths with COVID-19 vaccine exposures are identified monthly from the DPA. To 

increase sensitivity for finding stillbirths, late SABs also were identified. All potential cases were 

chart-reviewed by sites and then adjudicated by the Yale Obstetrics Team. The goals of chart 

review and adjudication were to confirm the outcome, estimate the date and gestational age at 

fetal demise, and identify possible etiology for the stillbirth. For confirmed stillbirths using the 

adjudicated date and gestational age at fetal demise, timing of any COVID-19 vaccine 

exposures were then reviewed.

During the surveillance period from December 2020 through July 2021, there were 11,300 live 

births in the VSD who received at least one COVID-19 vaccine dose during pregnancy. Among 

those, 670 possible stillbirths were identified to date using the DPA. Of these, 92 had a possible 

COVID-19 vaccine exposure during pregnancy. These 92 cases were chart-reviewed and 

adjudicated, with 66 for excluded for the following reasons: SAB (n=41) ongoing pregnancy 

(n=2), live birth (n=10), ectopic pregnancy (n=1) therapeutic abortion (n=9), and records not 

available (n=3). The majority were SABs rather than stillbirths, with 26 cases confirmed as 

stillbirths with one or more COVID-19 vaccine received during pregnancy.

To provide additional information on these 26 cases, the mean gestational was 29.5 weeks with 

a standard deviation of 6.6 weeks and the range of 20 to 40 weeks gestation. Of the 26 

stillbirths after chart review and adjudication by the Yale Obstetrics Team, 25 had at least one 

complication associated with stillbirth. Most common among these were umbilical cord or

placental complications, obstetric complications, and maternal comorbidities. In terms of timing 

between vaccinations and stillbirths for the full 26 cases, stillbirths occurred between 8 and 140 

days following Dose 1. For the 16 cases who received 2 vaccine doses in pregnancy, the timing 

between Dose 2 and stillbirth ranged from 3 to 112 days. In terms of the distribution of timing 

between vaccinations and stillbirths by manufacturer, 4 cases occurred following the J&J 

vaccine, 17 following Moderna, and 21 following Pfizer.

Of note, stillbirth surveillance is descriptive and there is no comparison group. In summary, 

monthly stillbirth surveillance was chart-reviewed and adjudication identified 26 stillbirths 

following COVID-19 vaccination from December 2020 through July 2021. Nearly all cases had 

one or more stillbirth risk factors. No concerning patterns were identified related to the timing of 

vaccine exposures or stillbirth etiology. A future case-control study is planned.
ACIP Meeting Summary September 22-23, 2021

47

Open Discussion

Ms. Hayes (ACNM) observed that having the racial diversity in VSD that is not available in vsafeSM is reassuring. In terms of the stillbirths that occurred with the Janssen vaccine, she asked 

whether there were any data on the links and if any clots formed among the women who 

received this vaccine.

Dr. Kharbanda indicated that she did not have the etiology in front of her for the stillbirths 

associated with the Janssen vaccines, but will follow-up with this information.

Dr. Ault recalled that there were data from the last pandemic showing that influenza vaccination 

actually protected against stillbirths. Therefore, he would be curious to see data in the future 

pertaining to whether COVID-19 vaccine also protects against stillbirths. In the news the week 

before, public health officials in Mississippi noticed a spike in stillbirths over the summer 

correlating with pregnant women getting COVID-19 disease. Rather than looking for negative 

associations, he would be interested in seeing positive associations in future research.

Dr. Poehling noted that as she is taking care of newborns, she is seeing an increase in maternal 

infections. The gestalt is that they seem to be more severe than they were earlier in the 

pandemic. She asked whether there are analyses underway about the impact of COVID-19 

infection in pregnant women in the VSD.

Dr. Olson indicated that Dr. Meaney-Delman would be presenting on some of the current 

epidemiology of pregnancy related to COVID-19 infections, which might help to answer this 

question.

Dr. Kharbanda added that as part of VSD’s safety work, they will be assessing infant outcomes.

Specifically, there are some studies looking at infant infections in the first 6 months of life.

Dr. Sanchez commented that they always have allowed rooming in with mothers and babies 

and anecdotally, it appears that slightly more of their newborns are testing positive at 24 to 48 

hours.

VaST WG Summary on Pregnancy

Dr. Keipp Talbot (VaST Chair) indicated that since February 2021, VaST initiated monthly and 

bi-monthly sessions with additional experts to review data on vaccine safety and pregnancy.

This is especially important as pregnant women were excluded from the original vaccine 

studies. There have been 6 maternal immunization-focused sessions during the VaST calls to 

date. VaST has reviewed data from VAERS, v-safeSM, v-safeSM pregnancy registry, VSD special 

studies, manufacturer data, and plans for further study.

VaST first reviewed data on vaccination of pregnant women from v-safeSM and the v-safeSM

pregnancy registry, and VAERS. VaST assessments conclude that a large number of pregnant 

women have chosen to receive COVID-19 vaccines in the US. A novel pregnancy registry in vsafeSM was established to monitor pregnancy and birth outcomes. Similar to non-pregnant

adults, pregnant women commonly report local and systemic reactogenicity, pain, fatigue, and 

headache. Pregnancy and birth outcomes following COVID-19 vaccination appear similar to 

rates reported in the literature. In April, May, and June 2021, VaST reviewed data from VSD that 

contributed to data from v-safeSM and VAERS showing no safety concerns. Specifically, SAB is 

from near real-time surveillance, stillbirth surveillance, and acute event surveillance.
ACIP Meeting Summary September 22-23, 2021

48

Maternal vaccination safety data from multiple sources are regularly reviewed in collaboration 

with pregnancy experts. VaSt is reassured about safety and maternal immunization. More data 

are emerging on the risk of COVID-19 for pregnant women, which can further inform the 

assessment of the risk and benefit of vaccination of this population. VaST will continue to review 

data on maternal vaccination and update the ACIP COVID-19 Vaccines WG, the ACIP 

Secretariat, and ACIP on a regular basis. 

Updates on COVID-19 and Pregnancy

Dr. Dana Meaney Delman (CDC/NCBDDD) provided updates on COVID-19 disease and 

pregnancy, including recent epidemiologic trends, VE, and CDC’s vaccine recommendations.

She noted that the term “pregnant people” would be used in this presentation as much as 

possible, but would maintain the term “pregnant women” for publications in which that term is 

used.

Beginning with recent trends in the epidemiology of COVID-19 among pregnant people, the 

epidemic curve of pregnant people with laboratory-confirmed SARS-CoV-2 infection reported 

through the National Notifiable Diseases Surveillance System (NNDSS) as of September 20, 

2021 reflects that 123,633 laboratory-confirmed SARS-CoV-2 infections had been reported 

among pregnant people. These case counts are likely an under-estimate of the true number of 

SARS-CoV-2 infections because pregnancy status is not known for all cases reported to CDC. 

Several things to note are that the case trend mirrors that of the non-pregnant population shown 

earlier in the day, with a clear fourth wave of infection associated with the Delta variant. The 

recent peak in pregnant cases began at the end of June and was higher than the Spring peak in 

cases seen in March. More than 1000 cases were reported among pregnant people weekly 

during the month of June. Case data does not routinely capture vaccination status. However, 

clinical partners have shared anecdotally that the majority of cases receiving care are 

unvaccinated pregnant persons. CDC hopes to have the vaccination status of cases in the 

future. It is important to note that there is a 2- to 4-week data delay. Therefore, the decrease in 

cases at the tail end should be interpreted with caution.

39

Overlaying the number of Intensive Care Unit (ICU) admissions and deaths among pregnant 

people on the epidemic curve, two very concerning trends have been observed and highlighted 

in recent news reports and in some of the conversations earlier. The first is the recent increase 

in ICU admissions. While the number of pregnant people admitted to the ICU was highest early 

in the pandemic and subsequently declined, there was an increased number of pregnant people 

admitted to the ICU in July and August. CDC is hearing from clinical partners that this trend in 

ICU admissions is continuing through September. Second, the number of deaths among the 

pregnant people has increased. The deaths reported in August represented the highest number 

of deaths reported in any month since the start of the pandemic. While CDC does not have the 

vaccination status for pregnant persons admitted to the ICU or for those who have died at this 

time, they do have preliminary data from other sources suggesting that these are predominantly 

unvaccinated person. For example, data in COVID-NET from 2021 indicate that approximately 

97% of pregnant women hospitalized with confirmed SARS-CoV-2 infection are unvaccinated.

These data may be under-estimates due to lag time in death reporting.

39 https://covid.cdc.gov/covid-data-tracker/#pregnant-population
ACIP Meeting Summary September 22-23, 2021

49

Increased ICU admissions and deaths are not entirely unexpected. It is known that pregnancy is 

associated with severe COVID-19 illness and that COVID-19 is associated with adverse

maternal, pregnancy, and neonatal outcomes. Based on forest plots from the living systematic 

review (LSR) by Allotey et al. and some additional data from a systematic review by Wei et al., 

pregnant women with COVID have statistically significant higher odds of ICU admission, 

ventilation, and extracorporeal membrane oxygenation (ECMO) compared with non-pregnant 

women of reproductive age with covid-19. Pregnant women with COVID-19 have a higher risk of 

maternal death, preeclampsia, preterm birth, and stillbirth than pregnant women without COVID. 

Neonates born to pregnant women with COVID-19 have higher risks of neonatal ICU admission 

when compared to those born to women without COVID-19. Of note, the absolute numbers of 

maternal deaths and stillbirths were low so the findings should be interpreted with caution.

In a CDC publication that assessed the risk of severe illness among symptomatic pregnant 

women with COVID-19 compared to symptomatic non-pregnant women with COVID-19 among 

approximately 400,000 women of reproductive age with laboratory-confirmed SARS-CoV-2

infection approximately, approximately 5.7% were pregnant. This analysis, which adjusted for 

age, race, ethnicity, and underlying medical conditions found a statistically significant increased 

risk of death for symptomatic pregnant women with COVID-19 compared to non-pregnant

symptomatic persons with COVID.

40 In addition to these findings, perinatal infection is another 

outcome of interest for pregnancies affected by SARS-CoV-2 infection. A recent analysis 

examined the results of SARS-CoV-2 PCR testing among approximately 26,000 neonates. 

Among these, 30% of neonates underwent testing and 4% of neonates born to women with 

SARS-CoV-2 infection were positive.

41 Other cohorts have estimated perinatal infection rates at 

approximately 1% to 2%.

42 While perinatal infection among neonates appears to be a rare 

outcome, it is yet another outcome to consider in the risk-benefit analysis of vaccination during 

pregnancy.

In terms of recent data on COVID-19 VE and pregnancy, there have been two published reports 

on VE and pregnant people from Israel.43 Both assess receipt of the Pfizer-BioNTech vaccine 

and matched vaccinated pregnant people 1:1 to unvaccinated pregnant people by 

demographics and clinical characteristics. The first study by Goldshtein et al. examines the 

cumulative incidence of infection over time. This is a retrospective cohort study from a large 

state-mandated Health Care Organization (HCO) in Israel. There were 202 SARS-CoV-2 

infections in the unvaccinated group and 118 in the vaccinated group. The authors concluded 

that mRNA vaccination compared with no vaccination was associated with a significantly lower 

risk of SARS-CoV-2 infection among pregnant people. The second study by Dagan et al. was 

an observational cohort study of pregnant women aged 16 years or older with no history of 

SARS-CoV-2 infection. Approximately 10,800 vaccinated pregnant women were matched 1:1 to 

unvaccinated pregnant controls. Looking at cumulative incidence of infection curves of SARSCoV-2 infection over time, the vaccinated and unvaccinated groups are similar until about Day 

14 post-vaccination when the incidence of infection in the vaccinated group begins to decline. In 

total, there were 235 infections in the unvaccinated group compared to 131 infections in the 

vaccinated group. The authors estimated that VE after the second dose 7 to 56 days later was 

40 Zambrano LD, Ellington S, Strid P, et al. Update: Characteristics of Symptomatic Women of Reproductive Age with LaboratoryConfirmed SARS-CoV-2 Infection by Pregnancy Status — United States, January 22–October 3, 2020. MMWR Morb Mortal Wkly 

Rep. ePub: 2 November 2020. DOI: http://dx.doi.org/10.15585/mmwr.mm6944e3external icon. 

41 Data from Surveillance for Emerging Threats to Mothers and Babies Network https://www.researchsquare.com/article/rs491688/v1

42 Mullins E, Hudak ML, Banerjee J, et al. Pregnancy and neonatal outcomes of COVID-19: coreporting of common outcomes from 

PAN-COVID and AAP-SONPM registries. Ultrasound Obstet Gynecol. 2021;57(4):573-581. doi:10.1002/uog.23619

43 https://jamanetwork.com/journals/jama/fullarticle/2782047; https://www.nature.com/articles/s41591-021-01490-8
ACIP Meeting Summary September 22-23, 2021

50

96% for any documented infection, 97% for symptomatic infection, and 89% for COVID-19

related hospitalizations. Overall, the VE estimate for pregnant women was not lower than that 

for the general population. More data are forthcoming on VE during pregnancy from CDC.

In addition to examining VE for preventing maternal infection, there is great interest in 

understanding if maternal vaccination confers immunity to the fetus or neonate. Current data 

from Gray et al.44 indicate that for pregnant people who have received an mRNA COVID-19 

vaccine during pregnancy, immunogenicity is similar to that observed in non-pregnant women. 

In addition, antibodies have been identified in umbilical cord blood and breast milk. These 

findings are encouraging, but not unexpected. More data are needed to determine whether 

maternal vaccination at different points during pregnancy can provide immune protection to 

neonates. NIH is beginning a multi-site study on this topic in which researchers will evaluate 

antibody responses in vaccinated participants and their infants among 750 pregnant individuals 

and 250 postpartum individuals. Participants and their infants will be followed through the first 

year after delivery. Antibody testing will be done on umbilical cord blood, breast milk, and blood 

from infants at 2 and 6 months after delivery. While immune protection to the neonate conferred 

by maternal immunization is an important area of study, it is important not to lose sight of the 

importance of protecting pregnant persons themselves. It is known that a healthy mother is 

critical for a healthy pregnancy and a healthy infant.

With respect to CDC’s updated clinical considerations for COVID-19 vaccine in pregnancy 

released on August 11, 202145, CDC made a strong recommendation for COVID-19 vaccination 

in pregnancy:

▪ COVID-19 vaccination is recommended for all people aged 12 years and older, including 

people who are pregnant, breastfeeding, or who trying to get pregnant now or might 

become pregnant in the future.

▪ Consistent with recommendations from professional medical organizations

This recommendation aligns with recommendations recently released from several clinical 

organizations, including the American College of Obstetricians and Gynecologists (ACOG), the 

Society for Maternal-Fetal Medicine (SMFM), and over 20 clinical professional organizations 

that have signed on to indicate medical consensus. These recommendations are based on the 

evidence to date on the safety, effectiveness, and health benefits of vaccination. It is known that 

pregnancy increases the risk for severe illness from COVID-19 and that COVID-19 is associated 

with adverse maternal, pregnancy, and neonatal outcomes. 

To summarize, there is evidence on the safety of mRNA COVID-19 vaccines during pregnancy,

and the information to date has been reassuring. There are recent studies on vaccine VE

demonstrating that vaccination during pregnancy reduces the risk of infection and 

hospitalizations. There also are studies that have identified vaccine antibodies in cord blood and 

breast milk, which are promising signs with regard to the potential for immune protection for the 

neonate. Despite all this information, current coverage with COVID-19 vaccination among 

pregnant people is very low.

46 Based on coverage of COVID-19 vaccination among pregnant

people reported to CDC’s VSD described earlier, only 30% of pregnant people were fully

vaccinated against COVID-19 prior to and during pregnancy as of September 11, 2021. While 

the overall trend in vaccination is upward, vaccination coverage both before and during 

44 https://pubmed.ncbi.nlm.nih.gov/33775692/

45 https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html#pregnant

46 https://www.cdc.gov/coronavirus/2019-ncov/vaccines/planning-for-pregnancy.htm
ACIP Meeting Summary September 22-23, 2021

51

pregnancy is far lower than hoped would be achieved. These low coverage rates are particularly 

concerning in light of the recent increases in cases, ICU admissions, and deaths among 

pregnant people.

47

CDC and its clinical partners are committed to improving vaccine coverage for pregnant people,

including encouraging vaccinations prior to, during, and after pregnancy. To highlight a few 

concrete efforts, CDC is assessing the reasons for vaccine hesitancy and planning to share 

personal stories of families. One of the most common reasons for vaccine hesitancy is concern 

about safety and theoretical risks of the vaccines. As evident from the presentations during this 

session, CDC is making every effort to disseminate information rapidly and broadly at ACIP, on 

the CDC website, through social media, and through CDC partners. The agency continues to 

address vaccine access issues and is working with clinical partners to encourage more 

clinicians caring for women to become vaccine providers. In addition, CDC is continuing to 

develop and provide resources to assist HCP and others who are having conversations with 

pregnant people about vaccines. Finally, the agency is working closely with clinical and public 

health partners to ensure consistent messaging about the need for COVID-19 vaccinations and 

to dispel myths about vaccines.

Taking off her CDC hat and putting on her clinical OBGYN hat, Dr. Meaney-Delman said she 

wanted to speak directly to the public listening during this meeting. It is known that pregnant 

people with COVID-19 can become very sick, some will die, and many will experience 

pregnancy and neonatal complications. It also is known that because of COVID, some children 

will grow up without their mothers. COVID-19 vaccines are known to be safe and effective. Dr. 

Meaney-Delman implored those who are pregnant, postpartum, breastfeeding, trying to get 

pregnant now, or might become pregnant in the future to please get vaccinated. 

Summary of Discussion

Dr. Ault noted that vaccine uptake in Black communities is about half of what Dr. MeaneyDelmand showed, so specific outreach is needed to this group who suffers from very high 

morbidity and mortality already at a baseline—specifically for subgroups of women who are 

under-vaccinated.

Dr. Meaney-Delman indicated that the highest uptake observed among pregnant people was 

among those who are Asian Non-Hispanic at 35.7%, the lowest uptake was observed among 

Black Non-Hispanic at 13.5%, uptake among Non-Hispanic Whites was 27.2%, and uptake 

among Hispanics was 21%. Everyone is interested in whether the Delta variant is associated 

with more severe disease in pregnancy. The only data she is aware of is from the UK, which 

does not have genomic sequencing and is basically time-series. The question remains 

regarding whether the Delta variant is associated with more severe illness or higher rates of 

perinatal infection. Right now the message is that people absolutely must be encouraged to get 

vaccinated.

Dr. Kotton noted that in general for the VSD and the v-safeSM registry, Black women were 

under-represented and she asked whether there are any plans to try to enhance that given how 

much the community has been impacted.

47 https://covid.cdc.gov/covid-data-tracker/#vaccinations-pregnant-women
ACIP Meeting Summary September 22-23, 2021

52

Dr. Olson responded that this is recognized as a deficiency of the current population pool on 

which they present data for the pregnancy registry. There are active plans to try to prioritize 

some groups who are significantly under-represented by the nature of how people enrolled and 

became participants of v-safeSM.

Dr. Kharbanda commented that for VSD, the data are based on members of the integrated 

health systems. The VSD as a whole has worked to increase diversity in the population. Denver 

Health was added as a VSD site and other sites that may be joining would increase diversity, 

but their data are yet to be included in the VSD work.

Dr. Sanchez observed that the adverse outcomes such as low stillbirths remained somewhat 

controversial in terms of the relationship, given that some of the studies have not shown that 

association in pregnant women with COVID-19 infection. If a booster dose is recommended for 

high-risk individuals, he wondered whether pregnant women would be included in that category.

In terms of stillbirths, Dr. Meaney-Delman indicated that they assessed the studies that were 

included in the Allotey systematic review. Many of those studies are from countries that have 

much better stillbirth surveillance than the US. She agreed that this question still remains, but 

the studies conducted in countries with better stillbirth surveillance are interesting albeit small 

numbers. Nevertheless, there are some concerns. She does not see a clear and compelling 

reason for this to be different than it is for the primary vaccine series, but she thought they 

would have to see what ACIP recommended. At this point it seemed premature to make specific 

recommendations for pregnant women.

Dr. Kharbanda added that in the VSD early in the pandemic CDC published some data in the 

MMWR on COVID infection and outcomes in pregnant women. One of the issues that has been 

discussed was assessed in a very small sample of women admitted for delivery who were found 

to have COVID infection versus women who showed symptomatic. In that sample, the 

proportion of women with stillbirths was higher than the VSD background rate. The VSD is again 

looking at continuing that surveillance and those data are currently being collected. It is

important to be careful in these evaluations during pregnancy to understand the right 

comparison group, because some of these observational systems are missing COVID infections 

that are asymptomatic during the course of pregnancy, but are capturing the more severe 

infections very well. They will continue to learn from that data, which continue to evolve.

Dr. Poehling reiterated that COVID infection during pregnancy is associated with increased 

negative maternal outcomes (ICU admissions, maternal deaths, stillbirths, increased NICU 

admissions for newborns, increased prematurity, increased preeclampsia). The data shown 

previously indicate that vaccine does not increase any of these outcomes. As Dr. Ault noted, 

there are data from influenza showing that vaccine actually reduces these. That highlights the 

importance of equitable access to COVID vaccines, encouraging persons who have increased 

risks for these negative outcomes to get vaccinated, and making sure everybody is captured.

Dr. Sanchez added that the data presented are very important and concerning, and pointed out 

that some of the consequences of prematurity actually may be unrelated to fetal or perinatal 

infant infection. Even the inflammatory changes that occur secondary to a COVID infection may 

result in placental inflammation, fetal inflammation, and prematurity leading to adverse 

consequences beyond some of the pregnancy outcomes that also should be evaluated.
ACIP Meeting Summary September 22-23, 2021

53

Dr. Meaney-Delman agreed and pointed out that the other thing they have to keep in mind is 

that if moms are really sick, sometimes delivering them is necessary to improve the ability to 

treat them. There is an element of iatrogenic preterm birth as well.

Dr. Fyhofer (AMA) said that speaking as a mom who hopes to be a grandmother very soon, she 

is very disappointed by the 30% uptake of the vaccine by pregnant women. Dispelling the myth 

that COVID vaccines are related to infertility has been one of the major challenges she has had 

in trying to overcome vaccine hesitancy. Many people do not understand that these vaccines 

actually protect moms during pregnancy. She greatly appreciates the outreach and consistent 

messaging and also thinks that a strong recommendation from CDC, ACOG, SMFM, and the 

other medical organizations has been very powerful.

Dr. Meaney-Delman agreed that it is incredibly important to continue with outreach and 

consistent messaging to address the myths. “Infertility” is defined as a year of trying to get 

pregnant unsuccessfully. It is hard to dispel that myth when there has not been sufficient time to 

conduct longitudinal studies on fertility, but it is known than many women have gotten pregnant 

subsequent to vaccination. There is not a biologically plausible reason to expect there to be an 

infertility concern associated with these vaccines, yet the myth has taken off.

Dr. Poehling highlighted the point that an increasing number of people have received vaccine 

before pregnancy. She emphasized that they all have a role in the effort to increase equitable 

distribution of vaccine, which will have a huge impact.

Dr. Cohn indicated that if there was an FDA authorization by noon the next day, the second day 

of the ACIP meeting would be convened as scheduled. If not, rescheduling information would be 

posted on the ACIP website. With no further business on the agenda, ACIP stood in recess for 

the day. 

Thursday: September 23, 2021

Welcome, Roll Call, Opening Remarks by Drs. Fink and Walensky 

Dr. Cohn (ACIP Executive Secretary, CDC) welcomed everyone to the second day of the 

September 22-23, 2021 ACIP meeting and noted that the updated agenda had been posted to 

the ACIP website.

Dr. Grace Lee (ACIP Chair) called to order and presided over the second day of the 12th ACIP 

meeting convened in 2021. She called the roll and established that no new COIs were 

identified/declared.

Dr. Dorin Fink (FDA Ex Officio ACIP Member) announced that late the previous day, FDA 

amended the EUA for the Pfizer-BioNTech COVID-19 vaccine to include use of a single booster 

dose administered at least 6 months after the primary series in the following populations: 

Individuals 65 years of age and older, individuals 18 through 64 years of age at high risk of 

severe COVID-19, and individuals 18 through 64 years of age whose frequent institutional or 

occupational exposure to the SARS-CoV-2 virus puts them at high risk of serious complications 

of COVID-19, including severe COVID-19. This was a regulatory action that followed FDA’s 

comprehensive and independent review of clinical trial data submitted by the vaccine 

manufacturer, as well as additional information concerning VE from real-world evidence and

observational studies inside and outside of the US presented and discussed at the VRBPAC
ACIP Meeting Summary September 22-23, 2021

54

meeting the previous Friday. Additionally, the FDA decision and construction of the authorized 

population for the booster dose took into account the feedback and recommendations that FDA

received from the members of the VRBPAC. 

Dr. Rochelle Walensky (CDC Director) made the following remarks: Good afternoon, 

everyone. Let me start with just a huge thank you to all of you. Over the past year, you have met 

18 times, mostly focused on COVID-19 and recommendations for vaccination. This is a 

tremendous amount of work, a tremendous amount of data to review, and in truth, a tremendous 

service. So, thank you. You’re tasked with difficult decisions, weighing the risks and benefits, 

extrapolating from sometimes a wealth and sometimes a paucity of data available, applying an 

equity lens to your actions, and doing all of this while reflecting on your own experiences on the 

pandemic frontline. What’s been your North Star and what drives my own thinking every day is a 

commitment to follow the science to improve the health of as many Americans as possible. Like 

you, I’m approaching this decision with an interest in doing what’s right for the public health and 

like you, I can’t close my eyes to my experience as a clinician. Collectively, we want to do what 

is right for the millions of Americans over the age of 65 and in LTCF who are at high risk of 

severe complications of COVID-19. Like you, I am also thinking about the 25-year-old man with 

cystic fibrosis who may walk into our clinic nervous about his risk for one more hospitalization

and also of the 35-year-old pregnant resident physician working in a Tennessee emergency 

room with a 1-year-old at home. It is in these complicated decisions where ACIP has always led, 

evaluating safety, equity, and access for those at risk. It is here where I am most grateful for 

your guidance.

I appreciate your meticulous review of the data available from CDC’s own cohort studies, from 

FDA’s review of Pfizer studies, and from public health partners and institutions around the 

world. These data are not perfect, yet collectively they form a picture for us and they are what 

we have in this moment to make a decision about the next stage in this pandemic. Thank you 

for leaning into this complexity, trying to fit the pieces together, and to come to the best 

conclusions. I’ve spoken with you previously and I hope some of you have heard some of my 

other public remarks. What you’re doing today is an essential part of the process. A thorough 

evaluation of data by this full committee is how we maintain a system that maximizes safety,

ensures effectiveness, lets data drive our decisions, and provides confidence to the American 

people. It is also how we strive to implement interventions that are equitable. Back in December

before I was even here, you created a blueprint for the country and the world—one that makes 

sure those at greatest risk for disease whether because of their age, underlying conditions, or 

occupational exposure had access to the most effective intervention we have to prevent 

symptomatic disease, severe disease, illness, and death from COVID-19.

Now, you have an opportunity to again lead our public health response with recommendations 

on how we can best utilize the tools we have to protect those at greatest risk. As you continue 

your discussion today, I make three commitments to you. First, as we move into a new stage of 

this pandemic and our vaccination program, I will not lose sight of our collective goal to protect 

as many people as possible from COVID-19 infection, hospitalization, and death. That means 

that as we operationalize a plan to provide booster doses to Americans, we remain committed 

to continuing our robust efforts to vaccinate as many people as possible here in America and 

around the world, and to continue to support and disseminate the public health interventions 

that we know work best to prevent disease. I see these as complementary. One can simply not 

replace the others. Second, we all recognize that the science and data of COVID-19 are moving 

faster than any data we have ever seen before. While I recognize the tremendously heavy lift of 

the past year, we all know that the pace is unlikely to let up anytime soon. We will continue this 

dialogue. You will have more data to review and more recommendations to make, and I will be 
ACIP Meeting Summary September 22-23, 2021

55

here with you. Third, the discussion of the data is critical. My clinical experience reminds me 

that in my most challenging cases, I learn more and make better clinical decisions by discussing 

with my colleagues and by hearing their points of view from their own clinical experience and 

review of the medical literature that I might not have considered. My academic experience

reminds me that in every research conference, I was enriched by hearing diverse perspectives. 

While we all plan to provide clear and aligned recommendations, the underlying discussion of 

diverse opinions and interpretations of the data only serves to strengthen our ultimate guidance.

You have a busy afternoon ahead of you, a lot of data to review, and a robust discussion to 

ensue. I will let you get to it and I will be watching and listening. Know that I am grateful for your 

efforts and that I so appreciate your expertise, your counsel, and your partnership. 

Coronavirus Disease 2019 (COVID-19) Vaccines

Introduction

Dr. Matthew Daley (Chair, ACIP COVID Vaccines WG) indicated that during the September 

23, 2021 COVID-19 Vaccines session, there would be presentations on the following topics:

❑ Public Comment

❑ Benefit/Risk Analysis of COVID-19 Vaccine Booster Doses 

❑ EtR Framework 

❑ Clinical Considerations

❑ Policy Options

❑ Votes on a BNT162b2 COVID-19 Vaccine Booster Dose

Public Comments

The floor was opened for public comment on September 23, 2021 at 12:20 PM ET. Given that 

many more individuals registered to make oral public comments than could be accommodated, 

selection was made randomly via a lottery. The comments made during the meeting are 

included here. Members of the public also were invited to submit written public comments to 

ACIP through the Federal eRulemaking Portal under Docket No. CDC–2021–0104. Visit 

http://www.regulations.gov for access to the docket or to submit comments or read background 

documents and comments received. 

Mr. Kermit Kubitz

Individual

Good afternoon. Thank you. My name is Kermit Kubitz. I look at things from the point of view of

a scientifically trained graduate of Cal Tech a long time ago. I believe booster shots of mRNA 

vaccines are valuable, safe, and justified relying principally, for example, today on Gruber's 

September 22nd slides CC7 and CC8 showing a large increase in protection after the third dose 

within seven days and a further increase one month after the third, including against the Delta 

variant as shown on slide CC8. I previously testified in support of EUA of the Pfizer vaccine in 

December 2020 and subsequently received the Moderna vaccine at a San Francisco VA 

hospital facility in Ft. Miley in February 2020. I have two sisters in their late 80s who have been 

vaccinated. One, immunocompromised with rheumatoid arthritis (RA), received a booster dose 

with no significant adverse effects, so I also rely on that personal experience. My friend Chuck 

Wolf from Caltech (California Institute of Technology) pointed out to me that we need to plan for 
ACIP Meeting Summary September 22-23, 2021

56

the logistics of boosters with three priorities: 1) the unvaccinated, 2) children 6 to 11, and 3)

boosters for other people. Approval of phased boosters for those over 65 and high risk, 

including from occupational exposure is not inconsistent with President Biden’s goal of boosters 

for all Americans because HCW, the elderly, first line essential workers, and those who are at 

high risk easily exceed 150 million people, which will take time to roll out. So we should plan,

and the CDC and FDA should plan for vaccination of HCW in groups, long-term care facilities in 

groups, and other rollouts. That is the most expeditious way of getting a boosters out there, 

including, for example, to my veteran friends at the veterans clinics across the country. I want to 

thank the ACIP for their work and suggest that it is important to also approve the Moderna 

mRNA vaccine as soon as possible so that the logistics of boosters can be easily accomplished 

for the maximum number of at risk people at the earliest possible date. Thank you very much. 

Mr. Edward Nirenberg

Individual

Good afternoon, everyone. I have had the honor of addressing you before and I am grateful to 

be able to speak to you again. I want to thank every member of ACIP once more for their 

stalwart efforts in leading us through these trying times, but I would like to draw attention to how 

those who wish to keep a pandemic burning through the US are exploiting public comments.

There are deceptive videos and papers featuring overconfident, undereducated, well-funded 

charlatans who use the opportunity of public comments to advance arguments that ACIP and 

VRBPAC meetings as those of authority. Some of the videos in particular use FDA or CDC 

logos to provide the similitude of authenticity. All use the docket number format of bringing

comment submissions and provide the .gov URL as a way to convince their acolytes that their 

counterfactual presentations are bombshell revelations from the government rather than the 

sophomoric meanderings of desperate hucksters that they actually are. It is heartbreaking to me 

that in my outreach for vaccination I’ve yet to encounter someone who has refused vaccination 

on the basis of a true premise. With the remainder of my time, I’d like to address some of these. 

The misuse of VAERS reports is salient. VAERS is a critical component of our vaccine safety 

network and they do a solid job of flagging adverse events for investigation in more robust 

systems like the VSD. But evidently that giant disclaimer that one must assent to have read 

before accessing VAERS is falling on deaf ears. VAERS is primarily for hypothesis generation,

early warnings, potential safety signals, and not a tool to investigate something in and of itself

as reports may be incomplete, coincidental, or even reflect phenomena which never occurred. 

The “Incredible Hulk Vaccine Side Effect” is a famous example. On a less lighthearted note, a 

VAERS report was issued months ago describing the death of a 3-year-old girl in Virginia 

following an mRNA vaccine for COVID-19 after a prolonged hospitalization. However, the 

vaccination in question could not record because it was done before clinical trials were even 

initiated for age groups. Similarly, many coincidental events will occur. Follow any random group 

of 10 million Americans for 2 months and you will see 4,000 heart attacks; 4,000 strokes; 60 

diagnoses of multiple sclerosis; 9,500 diagnoses of cancer; and 14,000 deaths. We have now 

vaccined 182.4 million Americans—a number that is still far too low. A great many coincidences 

will occur and seeking a causal link is best left to the experts. The spike protein is not toxic at 

concentrations in which is induced by vaccination. It would need to be roughly 10,000 to 

100,000 times greater in concentration than has been found in the plasma of vaccinated people

to start to reproduce the toxicities associated with it. Similarly, the mRNA vaccines are not 

associated with blood clots. The Johnson & Johnson vaccine is associated with what we are 

calling the disorder TTS at a frequency of about 7 per million doses and being greatest in the 

females younger age groups. There is no biological plausibility by which these vaccines can 

spontaneously exert or adverse effects months to years after vaccination. The lifetime of any 

vaccine component is a number measured in hours to days and the adverse effects should be 
ACIP Meeting Summary September 22-23, 2021

57

apparent by then. But out of an abundance of caution, EUA required immediate and 8 weeks of 

follow-up. Despite the first individuals receiving their vaccinations in March in the clinical trials, 

there are no credible reports of spontaneous adverse events outside that 8-week window, nor in 

anyone else, because this is a fantasy invented by anti-vaccine activist to scare people,

because when the facts don’t support your agenda and you’re an amoral narcissist, you lie. 

Thank you for this time. Please be safe. Please get vaccinated.

Mrs. Erica DeWald

Director, Strategic Communications and Partnerships

Vaccinate Your Family

Thank you so much. Good afternoon. I’m Erica DeWald, Director of Strategic Communications 

and Partnerships of Vaccinate Your Family (VYF). Thank you for the opportunity to address this 

committee today. Vaccinate Your Family watches each of your meetings with deep interest as it 

is our organization’s policy to follow ACIP recommendations. They’re the basis for our 

communications to both the public and our immunization partners. Throughout the development 

of the COVID-19 vaccines, the ACIP and FDA’s VRBPAC members have remained true to the 

science. That’s no small feat given the many pressures to move quickly and exercise every 

possible tool to end this devastating pandemic. Once again as pressure and confusion mount 

about the need for a booster dose of COVID vaccine, the VRBPAC and ACIP have proven the 

independence to science by not getting ahead of the data available to us. In order to make an 

informed decision about boosters, however, we need to understand the goals of a booster 

program in the US. We appreciate that Dr. Walensky, the CDC, and this committee are focused 

on that very issue. Setting a goal can help us better understand the role of a booster program, 

both for Pfizer and new future recommendations for Moderna or Janssen vaccines. It can also 

help us better design studies to identify whether our vaccination programs are moving us toward 

that goal. Additionally, clearly defined goals will help organizations, institutions, and health care 

providers combat misinformation around COVID-19 vaccines and all vaccines for that matter.

We also need to encourage politicians to support, not direct, public health. When the 

Administration announced boosters, the data to support or reject a booster was not yet publicly 

available and neither FDA nor CDC had even scheduled meetings of their independent advisory 

committees. That led to a lot of confusion and some communities’ mistrust. It further hurt our 

efforts to promote science-based public health recommendations, including vaccination. 

Confusion among the public will continue with announcements from political leaders perceived 

as independent bodies of the FDA and CDC. It also makes our work communicating clearly 

about the safety and necessity of vaccines even more difficult because it makes room for 

division and politicization of a critical public health issue. Now, to avert this confusion, we need 

ACIP to provide us clear direction around the definitions of those who are considered high risk 

and high occupational risk. We’re going to need very clear guidelines on who should receive a 

booster to prevent further confusion among the public and ensure an efficient, timely rollout of 

these boosters. It’s on ACIP’s recommendations to uphold rigorous processes and 

communicate the science clearly. This will ensure that the public continues to have faith in the 

overall vaccination program. Thank you for your careful deliberations and transparency. I 

appreciate your time.
ACIP Meeting Summary September 22-23, 2021

58

Dorit Reiss, JD

Professor of Law

University of California

Hastings College of the Law

My name is Dorit Reiss. I’m a Professor of Law at the University of California, Hastings College 

of the Law and a vaccine advocate. First, thank you for your thorough, transparent, and careful 

work on vaccines generally and COVID-19 vaccines specifically. I want to echo what my 

colleague Erica said that sticking to the science is not an easy thing these days. Your 

presentations provide substantial insight, a lot of information, and I know I always learn a lot as 

a lay person—even if most days like today you insist on having them at unreasonable East 

Coast times. I want to reiterate the point made to you by my friend and colleague Dr. Eve 

Switzer’s about 2 years ago. It’s when the science is uncertain that we need your guidance even 

more when the evidence can go either way. We are hearing experts disagree on the booster 

question, but a decision is needed one way or the other. I appreciate your willingness to face 

the hard decision and make recommendations. I hope that you consider equity at home and 

abroad when you do that and not just effectiveness. I want to follow up both on yesterday’s 

pregnancy data and on Erica’s point about the need for a clear definition by asking you to 

consider whether pregnant women should be considered high risk when you make your booster 

recommendation, even if they don’t really fit clearly into other categories. Two suggestions that 

are not about boosters: 1) If you’re looking for a place to increase transparency, the online 

advocates could use a more comprehensive discussion on VAERS on the back end. What 

happens to reports after they are submitted? How are they investigated? How do you avoid 

duplicates? Because that comes up quite a bit in questions from the vaccine-hesitant; and 2) 

I’ve said this before, transparency does not require you to provide a forum for all comments. I 

know that you get a lot of really helpful comments and I’ve read many of them, for example, Dr. 

Plotkin’s comments last week. I know many of the comments have been very valuable, but we 

also know that the opportunity to comment has been systematically misused by anti-vaccine 

advocates and activists to create propaganda videos that they use to promote misinformation

under the guise of comments to the CDC. Just this week, a comment to your sister committee 

VRBPAC misrepresenting COVID-19 vaccine as having high risk has been shared as, “the FDA 

said.” We know comments here were used same way. You’re not increasing transparency by 

allowing that. If you want to increase transparency, why not an alternative? You can, for 

example, set aside half an hour to address the major issues raised in the written comments and 

potentially also correct major errors like the federal government does in rulemaking. That will not 

only allow you to address comments, it will show that you’ve heard the comments and give your 

members an opportunity to consider the issues. Thank you.

Kevin Kavanagh, MD, MS

Health Watch USA

Thank you very much. Last Friday’s meeting to the FDA’s Vaccine and Related Biological 

Products Advisory Committee regarding boosters for the Pfizer-BioNTech vaccine resulted in 

recommending authorization of boosters for those 65 years of age and older along with those 

individuals who are at high risk for severe COVID-19. After the formal vote, a poll was taken and

the committee unanimously agreed that this recommendation should be extended to HCW and 

those who are high risk of occupational exposure to SARS-CoV-2. Thus, initially the committee 

focused on vaccinated individuals who are biologically at high risk of developing severe COVID19, but finally also recommended boosters for those at high risk of SARS-CoV-2 exposure. 

However, the degree of exposure is like being pregnant—you either are exposed or you are not. 

During a raging pandemic, action is needed now. We do not have the luxury of waiting for the 
ACIP Meeting Summary September 22-23, 2021

59

results of randomized controlled trials. I would like to encourage the committee to broaden the 

FDA’s recommendations. The following should be considered. First, at least one FDA 

committee member indicated that the main goal was to prevent severe disease which is defined 

as “hospitalizations or death.” However, this ignores the lasting and debilitating effects of Long 

COVID which can afflict 10% to 30% of those with even mild to moderate infections and pose a 

significant risk to our population. Second, Dr. Alroy-Preis, Israel’s Director of Public Health 

Services, testified that the Pfizer booster created a 10-fold increase in protection in 40 to 60 

year olds. With the disease profile of Delta markedly shifting to younger age groups, providing 

boosters to a wider range of individuals would be good public health policy. Finally, the United 

States has administered over 386 million doses of vaccines with an extraordinarily good safety 

record. The FDA committee had concerns regarding myocarditis in the young. However, this is 

a rare event occurring in approximately 1 in 5,000 young individuals. As stated by Dr. AlroyPreis, 95% of these cases were not severe. There is a much higher incidence of myocarditis in 

those who contract COVID-19. In view of the above, I would like to recommend reconsideration 

of offering Pfizer boosters to all who are 16 years of age or older or at least offering boosters to 

those who are 30 years of age and older, plus all individuals who are at risk of SARS-CoV-2

exposure. As a side note, we encourage the flu vaccine to be taken by all, not just those at high 

risk of severe disease or disease acquisition. We need to be consistent with our messaging. 

Thank you.

Laura Burns

Transplant Vaccine Study Group

Hello, my name is Laura Burns. I’m a double lung transplant recipient and a participant in all 

four of the Johns Hopkins studies on vaccine efficacy from first dose to fourth. I’m also a 

member of the Transplant Vaccine Study Committee Group originally formed by study 

participants, now with over 700 members. On behalf of myself and the group, I want to thank 

you from the bottom of my heart for authorizing additional doses last August. Indeed, many of 

us have been blessed with a dramatic response. Sadly, however, many remain with little or no 

response and all are still wary. Dr. Kotton spoke eloquently to our situation yesterday. If the 

committee should decide, as was suggested, that the goal of boosters is to prevent 

hospitalization and death, not infection, please remember that of the fully vaccinated, we are the 

ones who most likely would be hospitalized and die. Our families are scared to death that they 

could come home with a mild case and that so-called “mild case” will put us in the hospital. 

According to the FDA’s press release yesterday, those covered under today’s EUA are HCW, 

teachers, day care staff, grocery workers, among others. I’d like to address the term “among 

others” and hope you will give it wide latitude. Our families, friends, and colleagues are asked to 

cocoon us—to protect us by being fully vaccinated. With their immunity waning, that means 

boosters for them not just additional doses for us. One of our members writes, “Our family 

should get boosters. It’s critical to us that they don’t bring a breakthrough case into our homes.” 

Another, my husband, is not quite 65 but lives with me, an immunocompromised person. Sadly, 

his secretary refuses to get vaccinated. Will he be able to access a booster? Yet another, if a 

person feels that they need a booster to provide more protection for someone vulnerable to their 

household, then they should be able to do so without them having to go through all kinds of 

hoops. I agree and I urge you to implement this policy through self-attestation as you did for the 

immunocompromised. I also hope there will be a speedy way to get a Moderna booster, 

especially for the elderly. One way would be to simply include the 65 and over among the 

immunocompromised. The evidence you saw yesterday certainly supports that. Then they could

qualify under the current EUAs for both Moderna and Pfizer and get their boosters right away. 

One last word. Please get some help soon to the immunocompromised who got the J&J. They 
ACIP Meeting Summary September 22-23, 2021

60

have been left stranded. Thank you so much for all you do and for keeping us in mind during 

your deliberations. Thank you.

Ms. Katherine Falk

Parent and Vaccine Advocate

Hello, once more. I’m having a sense of déjà vu. My name is Katherine Falk and as always, I’m 

a parent and vaccine advocate from Oakland, California. Thank the committee again for all your 

hard work. I hope you’ll be able to continue independently assessing the data and making 

decisions free of pressure. In a way, it’s a more challenging time than it was before. In the last 

Administration, we had someone so hostile to public health. But now we have a President who 

is in some ways a little too enthusiastic. I would happily get a booster if that ends up being the 

best course of action, but as a layperson member of the public, I really look to the experts to 

look at what the data show, not just what I wish it would show or fear that it shows. In deciding 

on who should get boosters, I hope the committee will also keep equity in mind so immunity 

doesn’t become an even greater divide between haves and the have nots. I am glad to see you 

look specifically at how boosters might impact people in nursing homes. I hope there will also be 

efforts to look at boosters for other vulnerable segments of the population. Thank you. 

Harald Schmidt, PhD

Assistant Professor, Medical Ethics and Health Policy

Perelman School of Medicine, University of Pennsylvania

Next. We'll move on to Harold Schmidt. My name is Harald Schmidt and I’m an Assistant 

Professor of Medical Ethics and Health Policy at the University of Pennsylvania. I’d like to 

congratulate the ACIP chairs, members, and especially also staff for once more laying out with 

such clarity the hard tradeoffs we are facing. I’m also grateful to have the opportunity to share 

two recommendations that I believe matter for allocating boosters in ways that reduces rather 

than further increases inequity. Dr. Walensky rightly emphasized the importance of equity 

earlier. First, we should allocate boosters by universalizing the use of disadvantage indices such 

as the CDC Social Vulnerability Index. Secondly and directly related, we should recognize that 

the vast majority of people eligible for boosters are likely trusted vaccine ambassadors and draw

on them and the booster rollout to increase initial vaccinations in disadvantaged areas. At 

ACIP’s last meeting, several members rightly recognized that ethically, the case for boosters

can be near impossible to justify given the global vaccine access disparities. I emphatically 

agree with the sentiment and there is a clear moral imperative to keep up the pressure for global 

access and to learn the lessons for the next pandemic. That said, global allocation is not within

the ACIP’s agreements. Unfortunately, not recommending boosters in the US does not translate 

into vaccines where they are needed more. Still, ACIP’s recommendations do intersect with 

global and national equity and here is how. On April 19th when the entire US became vaccineeligible, the difference between fully vaccinated people in most of these disadvantaged groups

using the CDC’s Social Vulnerability Index was 4.5%. Currently, it is twice that rate and stands 

at 9%. Now in the worst case, these inequities are exacerbated if the US’s most privileged 

people quickly snap up boosters as they are made available while the more disadvantaged 

people fall further behind—whether we are talking about the most disadvantaged among the 65 

year olds or among high-risk groups since neither of these groups is homogeneous. The same 

applies once eligibility is widened to other groups. Alternatively, boosters can be used to reduce 

inequities and help achieve a less unfortunate scenario in terms of global disparities. We can 

still close the vaccine equity gap using the very metric that shows the disparity. Colleagues and 

I showed in Nature Medicine earlier this year that in the initial vaccine rollout, the majority of 

states use disadvantage indices in different ways, including increasing amounts of vaccines for 
ACIP Meeting Summary September 22-23, 2021

61

more disadvantaged areas, planning vaccination site locations, and targeted outreach and 

partnership. It would be useful for ACIP to recommend that all jurisdictions now adopt 

disadvantaged indices to promote equity. Plus, we now have tools such as Ariadne Labs’ free 

vaccine equity planner that can identify vaccine deserts and identify facilities in more 

disadvantaged areas that could potentially serve as vaccination sites. Access is still an issue. 

Finally, everyone who is eligible for vaccine is a potentially trusted ambassador. My expertise is

not in snappy slogans, but a campaign on the title such as, Get your booster and bring an 

unvaccinated friend or something better should be explored as a priority. Passing up the 

opportunity to increase first and second doses in rolling out boosters will not help equity. It is 

important to see the booster opportunity to close the gap in vaccination access across social 

disadvantage, especially also because it . . . [time expired].

Ms. Lynda Dee, JD

AIDS Action Baltimore

Hi. I’ve been with AIDS Action for 34 years and have learned the importance of evidence-based 

medicine the hard way. I’ve been a community rep on many FDA CDER antiviral advisory 

committee hearings, provided written comments for both VRBPAC and ACIP COVID-19 

meetings, and oral comments for all but one FDA COVID VRBPAC hearing. I’ve been very 

impressed with ACIP’s deliberations and decision-making process. The committee drills down 

into many real-world issues and provides answers to extremely important pragmatic questions

using a very organized process. That being said, we must acknowledge that the country is 

trapped in a COVID-19 nightmare. Americans are dazed and confused by vast amounts of data,

as well as mis- and dis-information. While it is not ACIP’s role to create policy, your decisions 

definitely promote policy. I’m here to ask you to help prevent severe COVID and death, 

transmission, vaccine hesitancy, booster confusion, and possible vaccine administration chaos. 

ACIP can help promote sound public health policies as well as maintain scientific integrity. You 

can accomplish this by recommending that the CDC’s current list of people with certain medical 

conditions who are more likely to experience COVID be used as the eligibility criteria for third 

doses of 162b2. This will provide the states with a familiar framework for booster eligibility, as 

well as more clarity for healthcare providers and a better understanding of complicated 

information from their communities. We need as much uniformity as possible so as not to further 

confuse the states and more importantly, the public. I would be remiss if I did not mention that 

people with HIV would have been entirely excluded, or almost entirely excluded, from COVID-19 

vaccine access without the actions of HIV activists. People with HIV were initially excluded from 

the Pfizer and Moderna Phase 3 trials. They were not included in the CDC’s vaccination

prioritization category until a few weeks before vaccines were available to the general public. 

Only a limited portion of people with HIV are included in the current immunocompromised list for 

third vaccinations. Inclusion of people with HIV and their advocates in ACIP or public comment 

sessions has also been minimal. I urge you to recommend that people with HIV and the many 

others listed in the current CDC medical conditions criteria for people who are more likely to 

experience severe COVID be included as one of your eligibility recommendations for third doses 

of 162b2. I only have time to address one eligibility recommendation. All of the 

recommendations based on the FDA EUA are provided in my written comments. I do support 

broad eligibility criteria for all FDA indications and for people of color based on many of the 

reasons that have already been discussed here today. I’d like to thank you for your dedication 

and commitment and for the opportunity to comment.
ACIP Meeting Summary September 22-23, 2021

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Mr. Brian Wilkins

Founder, COVID Legal USA

Editor-in-Chief, The COVID Blog

Journalist

I am Brian Wilkins, Founder of COVID Legal USA, Editor-in-Chief of The COVID Blog, and a 

longtime journalist. Everything I’m about to say can be verified and further researched that 

thecovidblog.com. Drene Keyes age 58 died 3 hours after her first Pfizer mRNA injection 

January 30, 2021 Gloucester, Virginia. Sara Stickles age 28 died 5 days after her second Pfizer

nRNA injection February 11, 2021 Beloit, Wisconsin. Benjamin Goodman aged 32 died 24 

hours after the Johnson & Johnson viral vector DNA injection March 14, 2021 New York, City. 

Cameron Thomas age 16 developed blood clots and died 11 days after her first Pfizer mRNA 

injection March 30, 2021 Waunakee, Wisconsin. John Francis Foley age 21 died 24 hours after 

the Johnson & Johnson viral vector DNA injection April 1, 2021 Cincinnati, Ohio. Griselda Flores

age 61 died 48 hours after her second Moderna mRNA injection May 3, 2021 Orange, 

California. Jacob Clynick age 13 developed myocarditis and died 3 days after his second Pfizer

mRNA injection June 16, 2021 Zilwaukee, Wisconsin. James Cooper Sawyer age 77 died 8 

days after his third Pfizer mRNA booster August 28, 2021 Cookeville, Tennessee. The list goes 

on and on and this happens in every country across the globe. The CDC chalks all of these 

deaths up as pure coincidence. The CDC’s own database, the Vaccine Adverse Event

Reporting System, has recorded 14,506 post-injection deaths in 2021 alone. But now, the CDC 

says their own databases are unreliable. The Nobel Prize-winning drug Ivermectin is now 

dismissed as “horse dewormer” by mainstream doctors and media, but there are more than 66 

peer-reviewed studies proving that Ivermectin is a highly effective treatment and prophylaxis 

against COVID-19. If you truly cared about public health, you would recommend Ivermectin for 

treatment and prevention protocols and stop the propaganda against this drug. But the CDC 

receives hundreds of millions of dollars from Pfizer, Baer, Merck, and other pharmaceutical 

companies so you cannot admit the truth and ruin your partners’ Emergency Use 

Authorizations. Further, the FDA receives 45% of its funding from user fees, meaning that these 

pharmaceutical companies pay the FDA while seeking approval of their drugs and medical 

devices. The conflicts of interest are blatant and frankly criminal pursuant to Title 18 of US Code 

Section 208. It’s indisputable fact on statistics from the CDC and Johns Hopkins University that 

a positive correlation exists between vaccination rates and COVID cases. As the previous rises, 

the latter rises. In sum, I pray that there’s enough humanity and critical thinking left on Earth for 

all involved in this global genocide to face Nuremberg-type trials. Again, visit thecovidblog.com

for more information on everything I just said. Thank you very much for giving me the 

opportunity to speak.

Ms. Sarah Barry

Pro-Vaccine Activist

My name is Sarah Barry. I am a pro-vaccine activist from Ohio, although some of you might 

know me better by my online handle, 42believer. Thank you all for continuing to dedicate your 

time and energy on this critical issue. I’m grateful to share my perspective with like-minded 

people while simultaneously drawing the ire of the exact same anti-vaccine activists who 

inspired me to start requesting a spot for public comment in the first place. In my past public 

comments, I’ve shared with you all the lengths anti-vax lobbyists went to in an attempt to censor 

me. Today, I’d like to share with you just how strong a hold anti-vax lobbyists are having on the 

legislative process in Ohio and update you on what the future holds for anti-vaccine legislation 

in the Buckeye State. First, HB248. HB248 is a bill that would make it illegal for anybody to 

require any vaccine—not just a COVID vaccine. A FOIA request revealed that not only would
ACIP Meeting Summary September 22-23, 2021

63

the language of HB248 created with the help of anti-vaxxers, but the amendments made to the 

bill were also made because of anti-vaxxers. Further FOIA requests of text messages combined 

with some Facebook posts proved to me that not only was the language of the bill written by 

anti-vaxxer lobbyists, but they were significantly involved in the hearing process for HP248. On

May 21st, Representative Jennifer Gross texted the Chairman of the Health Committee, Scott

Lipps, referencing the anti-vaxxer lobbyists. She claimed that they are, “picking and choosing 

and promising witnesses without discussing it with me” and also that they “decided the 

schedule.” After reviewing Facebook comments, a member of that same lobbyist group who 

attended a meeting with Gross and Lipps said that the changes to testimony protocol were

discussed in that meeting. Every time I went to submit my own testimony for HB248, I was 

denied the opportunity to give in-person testimony. Although I don’t have direct evidence of 

them using this new process to censor me yet again, I’m smart enough to read between the 

lines. Fortunately, HB 248 is dead thanks to Sherri Tenpenny turning Ohio into a national 

laughingstock with her unhinged testimony and the subsequent infighting amongst the antivaccine lobbyists. Unfortunately, anti-vax sentiments are still percolating in the Ohio legislature. 

Multiple other bills targeting vaccine requirements have been introduced and as I speak, there 

are plans by the Republican leadership to introduce their own version of such a bill. I have even 

heard that they plan to bring this new bill to a floor vote “as early as next week,” which would 

certainly not give me or anybody else the requisite time to speak in opposition. Since I feel I 

have no other option, this is my public plea to Representative Bob Cupp, Representative Tim 

Ginter, Representative Bill Seitz, Representative Rick Carfagna, Representative Don Jones, 

and Representatives Cindy Abrams. I was born and raised in Ohio and I’ve watched with 

dismay as anti-vax lobbyists plant misinformation in the minds of your colleagues. I urge you to 

reject anti-vax legislation that goes against public health and that includes any bill that interferes 

with employers’ right to keep the workers and customers safe. I thank ACIP once again and I 

urge all Americans to pay attention to their state legislatures, lest they become as anti-vaccine 

as Ohio has. 

COVID-19 Vaccine Booster Doses: Benefit-Risk Discussion

Dr. Megan Wallace (CDC/NCIRD) presented on the benefits and risks of the Pfizer-BioNTech

vaccine booster doses. To assess the benefit-risk balance of a booster dose, a direct estimation 

approach was used similar to that presented to ACIP in previous benefit-risk discussions. 

Benefits were calculated per million doses of Pfizer-BioNTech COVID-19 vaccine booster. The 

analysis was stratified by 4 age groups: 18-29 years, 30-49 years, 50-64 years, and ≥65 years. 

A 180 day time horizon was used. Calculations for the benefits of vaccination were based on

age-specific case incidence data from CDC48 and hospitalization data from COVID-NET.

49 For 

VE for the primary series, age-specific pre-booster EV estimates were averaged from 4 

platforms. Given that VE after a booster dose is unknown, post-booster VE was assumed to be 

95% for hospitalization and 90% for infection for this analysis. For the point estimates for the 

current age-specific VE for hospitalization, estimates were averaged from 4 platforms: COVIDNET50, Scobie et al.51, VISION52, and IVY Network53 for the base case. For harms, the analysis 

focused on the risk of myocarditis following a booster dose. While it is acknowledged that there 

may be other risks such as anaphylaxis, they were not considered in this analysis. Like benefits,

harms were calculated per 1 million booster doses. Because myocarditis incidence following a 

48 https://covid.cdc.gov/covid-data-tracker/#trends_dailycases

49 https://gis.cdc.gov/grasp/COVIDNet/COVID19_3.html

50 https://www.medrxiv.org/content/10.1101/2021.08.27.21262356v1

51 https://www.cdc.gov/mmwr/volumes/70/wr/mm7037e1.htm?s_cid=mm7037e1_w

52 https://www.cdc.gov/mmwr/volumes/70/wr/mm7037e2.htm. Using Pfizer specific estimate.

53 https://www.cdc.gov/mmwr/volumes/70/wr/mm7034e2.htm
ACIP Meeting Summary September 22-23, 2021

64

third dose is unknown, input was based on VAERS data post-Dose 2. In terms of reporting rates 

of myocarditis following Pfizer-BioNTech COVID-19 vaccination per million doses administered 

by age and dose number in the 7-day risk period following vaccination, the incidence of 

myocarditis was higher among young males following Dose 2.54 Sensitivity analyses were 

performed to account for the large amount of uncertainty in the model input. Estimates were 

varied for how much a booster dose would increase VE and for current VE and modeled 

increased VE waning by decreasing the current VE estimate by 5% intervals. Finally, variable 

risk was modeled by considering myocarditis incidence seen after Dose 2 and 2 times that seen 

after Dose 2.

The framework by which the booster dose benefit-risk analysis was approached was first to 

evaluate the benefits versus the risks of the COVID-19 booster dose. Then the differential 

benefits of booster doses were analyzed by age groups. Finally, the differential benefits of 

booster doses were compared with the primary series. This presentation followed the same 

sequence. In the base case scenario for benefits and risks after Pfizer-BioNTech COVID-19 

booster dose, the VE for hospitalizations averaged from the 4 platforms was used. It was 

assumed that a boost would bring VE to 95% and that the myocarditis risk would be equivalent 

to that seen after Dose 2. For all age groups, more COVID-19 hospitalizations would be 

prevented than myocarditis cases expected. However, this is particularly true for those aged 65 

years and older. Building upon the base case, it was next assumed that myocarditis risk was

double that seen after the second dose. Assuming this higher incidence of myocarditis, more 

hospitalizations were still prevented than myocarditis cases expected for each age group.

However, it is important to note that myocarditis risk was not evenly distributed by sex after

Dose 2. When the risk distribution seen after Dose 2 is applied, 4 cases of myocarditis per 

million doses would be expected among females aged 18-29 years and 48 per million doses 

among males.

The scenario to further explore the benefits and risks after Pfizer-BioNTech COVID-19 boosters

for persons aged 18-29 years with varying pre-booster VE by sex, hypotheticals were used and 

pre-booster VE was varied for hospitalization. COVID-19 hospitalization rates were stratified by 

sex and it was assumed that the booster dose would bring VE to 95%. The myocarditis risk was 

assumed to be equivalent to the risk seen after Dose 2. To acknowledge the variability of 

myocarditis risk by age, a range of risks was presented which showed a risk in 25-29 year olds 

on the low end and an 18-24 year old risk seen on the high end. When taking sex-specific 

hospitalization rates and myocarditis risk into account, more COVID-19 hospitalizations were 

expected in cases of myocarditis for all but the highest starting VE. A limitation of this model is 

that a constant incident was assumed over the 180 day time horizon. To address this, another 

scenario was run in which incidence rates were 1/3 of the current rate and were similar to the 

rate seen in June and July of this year. In the scenario of lower incidence, a lower pre-booster

VE is needed for the benefits of a booster dose to clearly outweigh the risks in males aged 18 to 

29 years.

COVID-19 infection prevented is another potential benefit of COVID-19 boosters. In this

analysis, potential cases prevented were included by assuming a current VE for infections of

around 78% from Scobie et all.

55 and a boosted VE against infection of 90%. When considering 

infections as the benefit of interest, giving a million booster doses could prevent between 7,500 

to 10,000 infections over the next 6 months, with the most infections prevented among those 

aged less than 50 years.

54 Data as of August 18, 2021: https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2021-08-30/03-COVID-Su-508.pdf

55 https://www.cdc.gov/mmwr/volumes/70/wr/mm7037e1.htm?s_cid=mm7037e1_w 
ACIP Meeting Summary September 22-23, 2021

65

Looking more explicitly at the differential benefits and risks of booster doses in persons aged 

18-29 years compared with those aged 65 years and older, the analyses continued to build on 

the base case for pre-booster VE against hospitalization. While the benefits outweigh the risks 

for most potential post-booster VE estimates, the benefits obtained by those aged 65 and older 

were an order of magnitude larger than benefits obtained by those aged 18 to 29 years. Another 

way to think about this is the number needed to vaccinate (NNV). The NNV with a booster dose 

to prevent 1 hospitalization over 6 months in those aged 65 years would be 481 people.

Prevention of 1 hospitalization in persons aged 18-29 years would require vaccinating 8,738

people. Prevent 1 hospitalization, 19 times as many 18-29 year olds would need to be 

vaccinated compared to those aged 65 and older. As mentioned previously, the scenario is 

based off of current incidents, which is high. As incidents decreases, the NNV will increase. The 

NNV is substantially lower and more evenly distributed by age for infections compared to 

hospitalization.

In the scenario looking at the relative benefits of booster doses versus primary series 

vaccination with Pfizer-BioNTech COVID-19 vaccine, the base case VE for hospitalization was 

used that was averaged from the 4 platforms and the VE for infections estimated from Scobie et 

al. It was assumed that a booster dose would bring VE to 95% for hospitalization and 90% for 

infection. To calculate hospitalizations prevented by a primary series, it was assumed that 1

million doses were used to provide 500,000 primary series and that the primary series provides 

95% VE for hospitalization and 90% for infection. The NNV was substantially lower for all age

groups for the primary series as compared to the booster dose. For those aged 65 and older, 10 

times as many people would need to be vaccinated with a booster dose to prevent 1 

hospitalization compared with primary series vaccination. For persons aged 18-29 years of age, 

the NNV was 22 times as high for booster compared with the primary series vaccinations.

This analysis has several important limitations. The benefit-risk analyses are very sensitive to 

pre-booster VE estimates and effectiveness estimates for Delta variants are limited. The 

available age-specific US data are based on month of COVID-19, not on duration since 

vaccination. The preferred pre-booster data would measure effectiveness by duration since 

second dose. Post-booster effectiveness and post-booster myocarditis risks are unknown and 

are based on available evidence from the primary series. Early data have corroborated these 

estimates. Finally, the model assumes static incidence and VE over a 6-month period.

In summary, this is a direct benefit-risk assessment for Pfizer-BioNTech COVID-19 vaccine 

booster and myocarditis, which considered individual benefits of vaccination versus individual 

risks. Using current VE estimates, the benefit-risk balance is most favorable for adults 65 years 

of age and older and shows smaller benefit for the population less than 65 years of age. The 

benefits increase in scenarios with lower VE for prevention of hospitalization in cases, which 

could be seen with those at higher risk of severe disease. The risk of myocarditis after a third 

dose of mRNA vaccine may vary by age and sex. The highest rates of myocarditis after the 

second dose were seen in younger males. This presentation focused on the benefits and risks 

of the Pfizer-BioNTech COVID-19 booster dose by age. For benefits, the focus was on the 

prevention of COVID-19 hospitalizations in cases, but there may be other additional benefits 

such as prevention of deaths and possible prevention of transmission. For risks, the focus was 

on the risk of myocarditis following vaccination. However, there may be other risks such as 

other rare events after mRNA vaccines and short-term reactogenicity.
ACIP Meeting Summary September 22-23, 2021

66

Discussion Points

Dr. Maldonado (AAP) noted that in California it is known that among Latinos, 39% of deaths 

occurred among those under 65 years of age as compared to 15% among White individuals and 

31% among Black individuals. In terms of the data on race and ethnicity, there may be a 

disproportionate number of deaths and potentially hospitalizations for under-represented 

minority groups under 65 years of age. With that in mind, she wondered whether the modeling 

team was able to parse the data out to look at race and ethnicity.

Dr. Wallace indicated that while this was not covered in this analysis, it would be covered more 

explicitly in the upcoming EtR presentation.

Regarding the comment at the end of the presentation that the risk of transmission was not 

considered in the modeling, Dr. Gluckman (AHIP) recalled that in the approvals pertaining to 

Prevnar dosing in the elderly, it was eventually concluded that the biggest impact had to do with 

immunization using that vaccine in younger people. He asked whether there would be a way to 

think about the extrapolation about the benefits in people at higher risk by reducing the amount 

of circulating virus and whether that is important.

Dr. Wallace agreed that while this is an important observation, at this point there are no data on 

transmission or how booster may impact transmission.

EtR Framework: Booster Doses of Pfizer-BioNTech COVID-19 Vaccine

Dr. Sara Oliver (CDC/NCIRD) presented the EtR Framework for Booster Doses of PfizerBioNTech COVID-19 Vaccine. She reminded everyone that the EtR Framework is the structure 

to describe information considered before ACIP makes vaccine recommendations. This 

provides transparency around the impact of additional factors on deliberations when considering 

a recommendation. Because questions around the vaccine policy for booster doses are 

complex, some adaptations were required of the standard EtR recommendation framework. The 

standard EtR domains include: Public Health Problem, Benefits and Harms, Values, 

Acceptability, Feasibility, Resource Use, and Equity.

This presentation walked through the through the public health problem to evaluate whether 

booster doses are needed, the balance of benefits and harms for booster doses by age, values 

and acceptability in terms of whether people want a booster dose, feasibility in terms of how 

booster doses would be implemented, resource use with regard to the costs associated with 

booster doses, and the equity considerations for booster doses. FDA issued a regulatory 

allowance the previous evening, for which ACIP would now consider recommendations for use.

This presentation focused on who should be recommended to receive a Pfizer-BioNTech 

COVID-19 booster dose under the current EUA based on the balance of benefits and risks.

Turning to the public health problem regarding whether booster doses of COVID-19 vaccines

are needed, the US is currently experiencing a large surge second only to the one seen in the 

past winter. The recent surge may have peaked, especially in some states that experienced

their Delta surgery earlier.

56 Over 182 million people in the US are fully vaccinated with a 

COVID-19 vaccine primary series.57 Comparing COVID-19-associated hospitalization rates 

among the vaccinated compared to the unvaccinated population, among adults 65 years of age

56 https://covid.cdc.gov/covid-data-tracker/#trends_dailycases; Accessed September 22, 2021

57 https://covid.cdc.gov/covid-data-tracker/#vaccinations_vacc-total-admin-rate-total; Accessed September 22, 2021
ACIP Meeting Summary September 22-23, 2021

67

and over, the incidence was 13 times higher in unvaccinated. For those less than 65 years of 

age, the hospitalization rates are 22 to 23 times higher in unvaccinated individuals.58 In terms of 

comparing incidence rates for COVID-19 hospitalizations in the US with severe disease in Israel 

among vaccinated people, July 2021 was when overall case rates were beginning to increase in 

both countries. The rates for Israel were approximately 2 to 5 times the rate for the US.59

Regarding whether VE rates are waning by age in the US, some decreases have been seen in

VE estimates for the last 1 to 2 months. This could be due to both waning immunity due to time

since primary series and the impact of the Delta variant. In late May, Delta was around 7% of 

sequenced isolates. By mid-July, it was 94% a sequenced isolates. To summarize VE by age in 

the US over time, significant declines have occurred in VE against infection in individuals ≥65 

years of age for mRNA products in the Delta period. Smaller declines were observed in VE 

against hospitalization in individuals ≥65 years of age, but were more substantial than in 

younger populations. Among adults <65 years of age, vaccines remain effective in preventing 

hospitalization and severe disease. However, the vaccines may be less effective in preventing 

infection or symptomatic illness due to waning over time and the Delta variant.

60

In terms of whether VE is waning for those with underlying medical conditions, there is not a 

significant difference among VE over time for medical conditions that had enough persons able 

to provide an estimate.61 Another study evaluated VE against infections among US veterans 

with underlying medical conditions in the pre-Delta time period. At that time, VE was high for 

both those with a low CCI and a higher CCI.

62 To summarize VE by underlying medical 

condition, there are currently limited data to evaluate VE by a variety of underlying medical 

conditions. The current data show limited waning in those with at least one underlying medical 

condition. However, it is important to note that these estimates exclude immunocompromised 

individuals. In addition, the estimates may not represent effectiveness across all underlying 

medical conditions. VE studies cannot produce estimates for rare and possibly more severe

underlying condition. There is a spectrum of underlying medical conditions with a range of 

severity, and many have a varying impact in effectiveness and are not fully represented in the 

estimation here.

58 Havers et al. https://medrxiv.org/cgi/content/short/2021.08.27.21262356v1. COVID-19-associated hospitalizations among 

vaccinated and unvaccinated adults ≥18 years - COVID-NET, 13 states, January 1-July 24, 2021 0 20 40 60 80 100 120 Rate per 

100,000 population Week ending 0 20 40 60 80 100 120 140 160 180 200 Rate per 100,000 population Week ending Vaccinated 

vs. Unvaccinated † 23x higher 22x higher 13x higher 1

59 Scobie HM, Johnson AG, Suthar AB, et al. Monitoring Incidence of COVID-19 Cases, Hospitalizations, and Deaths, by

Vaccination Status — 13 U.S. Jurisdictions, April 4–July 17, 2021. MMWR Morb Mortal Wkly Rep 2021;70:1284–1290. Goldberg 

et al. Waning immunity of the BNT162b2 vaccine: A nationwide study from Israel.

https://www.medrxiv.org/content/10.1101/2021.08.24.21262423v1.full-text

60 Rosenberg ES, Holtgrave DR, Dorabawila V, et al. New COVID-19 Cases and Hospitalizations Among Adults, by Vaccination 

Status — New York, May 3–July 25, 2021. MMWR Morb Mortal Wkly Rep. ePub: 18 August 2021; Nanduri S. Effectiveness of 

Pfizer-BioNTech and Moderna Vaccines in Preventing SARS-CoV-2 Infection Among Nursing Home Residents Before and During 

Widespread Circulation of the SARS-CoV-2 B.1.617.2 (Delta) Variant; National Healthcare Safety Network, March 1–August 1, 

2021. MMWR Morbidity and Mortality Weekly Report. 2021 2021;70.; Fowlkes A, Gaglani M, Groover K, et al. Effectiveness of 

COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Frontline Workers Before and During B.1.617.2 (Delta) Variant 

Predominance — Eight U.S. Locations, December 2020–August 2021. MMWR Morb Mortal Wkly Rep. ePub: 24 August 2021; 

Puranik A, Lenehan PJ, Silvert E, et al. Comparison of two highly-effective mRNA vaccines for COVID-19 during periods of Alpha 

and Delta variant prevalence. medRxiv 2021.08.06.21261707; Keehner J, Horton LE, Binkin NJ et al. Resurgence of SARS-CoV2 Infection in a Highly Vaccinated Health System Workforce. NEJM, September 1, 2021. DOI: 10.1056/NEJMc2112981

61 CDC unpublished, IVY Network

62 Butt AA, Omer SB, Yan P, Shaikh OS, Mayr FB. SARS-CoV-2 Vaccine Effectiveness in a High-Risk National Population in a Real

World Setting. Ann Intern Med. 2021;M21-1577.
ACIP Meeting Summary September 22-23, 2021

68

Regarding whether VE is waning for those with high-risk occupations, VE against infection has 

waned in recent months among HCP, first responders, and frontline workers.63 To summarize 

VE by high-risk occupation, effectiveness among healthcare and other frontline essential 

workers is similar to estimates for the general population for the same age where declines have 

been seen against infection recently. Severe disease among vaccinated essential workers is 

rare. The previous data demonstrated that VE is waning against infection in this population. It is 

known that the impact of a lower VE against infection may be different among healthcare and 

other frontline essential workers. It also is known that many in this group were prioritized for 

early doses of COVID vaccine and will have had longer duration since their primary series.

With regard to how these data vary by vaccine, data show that VE varies by initial vaccine type. 

Protection against hospitalization for mRNA vaccines is high, though it is known that this may 

vary somewhat by age. Protection against infection is lower for all vaccine types.

To summarize for the public health problem, hospitalization rates are 10 to 22 times higher in

unvaccinated compared to vaccinated adults. Over 182 million people are fully vaccinated in the 

US. Although COVID-19 continues to be a public health problem, among persons who have 

received a primary series, data support continued protection against hospitalization and death. 

Long-term outcomes among infections after vaccination must continue to be followed.

Turning to the balance of benefits and harms for booster doses by age, the first question 

regards whether booster doses of the COVID-19 vaccine safe and immunogenic, which is the 

GRADE aspect of the EtR. In terms of the PICO question for GRADE, the population included 

persons 18 years of age and over who completed a primary series at least 6 months prior. The 

intervention was a single dose of the Pfizer vaccine and the comparison was no booster dose. 

The outcomes included: Symptomatic laboratory-confirmed COVID-19, hospitalization due to 

COVID-19, death due to COVID-19, transmission of SARS-CoV-2 infection, SAEs, and 

reactogenicity. In terms of evidence retrieval, 2 WHO records were identified from International 

Vaccine Access Center (IVAC) systematic review of COVID-19 vaccine literature and 2 were 

identified through other sources. All 4 were assessed for eligibility and all 4 were included in the 

evidence synthesis.

There were 2 available observational studies for booster doses, both from Israel.64 Israel began 

administering a third dose for immunocompromised individuals on July 12, 2021 and for all 

residents 60 and over on August 1, 2021. Both studies used large data systems and included 

individuals who had received their second dose at least 5 months prior to booster 

administration. For both studies, the control population were individual who had completed a 2-

dose series—not the unvaccinated population. Both studies have limited follow-up periods, with 

a maximum of 21 days for documented infection and 16 days for severe disease. For GRADE 

purposes, pooled estimates were not generated because the 2 studies had overlapping study 

populations. The most representative study, Bar-On et al., was used for GRADE assessments. 

One study was peer-reviewed and one was a preprint. Both studies were conducted in Israel, 

which required a minimum interval of 5 months following the second dose for booster dose 

eligibility. The first study by Bar-On et al was used for GRADE because it included nationwide 

63 Fowlkes A, Gaglani M, Groover K, et al. Effectiveness of COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among 

Frontline Workers Before and During B.1.617.2 (Delta) Variant Predominance — Eight U.S. Locations, December; 2020–August 

2021. MMWR Morb Mortal Wkly Rep. ePub: 24 August 2021; Keehner J, Horton LE, Binkin NJ et al. Resurgence of SARS-CoV-2 

Infection in a Highly Vaccinated Health System Workforce. NEJM, September 1, 2021. DOI: 10.1056/NEJMc2112981

64 Bar-On et al. BNT162b2 vaccine booster dose protection: A nationwide study from Israel. medRxiv preprint Autust 31, 2021. doi: 

ttps://doi.org/10.1101/2021.08.27.21262679; and Patalon et al. Short Term Reduction in the Odds of Testing Positive for SARSCoV-2; a Comparison Between Two Doses and Three doses of the BNT162b2 Vaccine. MedRxiv, August 31, 2021
ACIP Meeting Summary September 22-23, 2021

69

data. The VE comparing booster dose to a 2-dose series was 91%, with a 95% confidence

interval of 90.4% to 91.9%.

The GRADE evidence types for the outcome symptomatic lab-confirmed COVID started at 1. 

Very serious risk of bias was present. The Phase 3 trial among adults 18-55 years had 306 

participants and the Phase 1 trial among adults 65-85 years had 12 participants. Although a 

subset of participants were randomized to a booster dose or other investigational vaccine, none 

was randomized to placebo. The only data available for GRADE were from a pre/post booster 

analysis and not according to randomization. Very serious indirectness was also noted because 

VE was inferred from immunobridging to the same participants after Dose 2 and because the 

formal immunobridging analysis was only performed on participants ages 18-55 years, which 

may not be representative of older participants. The ratio of GMTs of neutralizing antibodies at 1 

month after booster dose was noninferior to the GMT detected at 1 month after dose 2. The 

evidence was Type 4, or very low, for this critical outcome.

The observational study for symptomatic laboratory-confirmed COVID-19 started at an evidence 

level Type 3, or low. Very serious concern for indirectness was noted because the study 

outcome was any SARS-CoV-2 infection, which was an indirect measure of the PICO outcome 

of symptomatic COVID. Additionally, the short duration of follow-ups likely limited an accurate 

assessment of VE. No serious concerns for risk of bias, inconsistency, or imprecision were

noted. The relative risk of 0.09 favors a booster dose vaccination. However, the absolute effect 

was small with an estimated 277 fewer cases per 100,000. The evidence type was 4, or very 

low, for this observational study data.

One observational study provided data for the outcome of hospitalization for COVID. The initial 

evidence type of 3 was downgraded for very serious indirectness. The outcome of the study 

was severe COVID, which is an indirect measure of the PICO outcome for hospitalization for 

COVID. Additionally, the short duration of follow-up likely limited an accurate assessment of VE. 

The relative risk of 0.05 favored vaccination. However, the absolute effect was small with an 

estimated 26 fewer cases of severe COVID per 100,000. The evidence type was 4, or very low,

for this critical outcome. 

Phase 3 RCT data provided information for SAEs and reactogenicity. For both outcomes, a very 

serious risk of bias was present because a non-random subset of participants who received the 

booster dose are compared to the safety population from the 2-dose efficacy trial at the time of 

the BLA. For SAEs, there also was serious concern for indirectness and very serious concern 

for imprecision. The relative risk was 0.02 with wide confidence intervals that did not rule out

harms. The evidence was Type 4, or very low, for this critical outcome. For reactogenicity, there 

was serious concern for indirectness and imprecision. The relative risk was 0.06, indicating a 

lower risk of Grade 3 reactions in the booster compared to the primary series. The evidence 

type was 4. or very low.

While not specifically included in GRADE, a finding mentioned by Pfizer the previous day was 

noted. There were 5% percent of individuals in their Phase 3 trial who received the booster 

doses that reported lymphadenopathy. This was all axillary lymphadenopathy, and only 1 

severe event of lymphadenopathy was noted. This was reported more frequently following 

booster doses at 5.2% compared to 0.4% after the primary series.65

65 Clinical trial data requested by CDC
ACIP Meeting Summary September 22-23, 2021

70

The experience from Israel can also be used to inform knowledge about the safety of booster 

doses. Again, the rollout initially began with adults over 60 years of age and was expanded to 

those over 12 years of age at the end of August. Around 2.8 million third doses have been 

administered to persons 12 years of age and over, but most of those doses currently have been 

given to persons over 60 years of age. The rates of reported systemic, local, neurologic,

allergic, and other reactions were lower after Dose 3 than after Dose 1 or 2, but there is likely

under-reporting. Israel has noted one case of myocarditis to date after a booster dose in an 

individual 30 years of age and over. Due to limited follow-up time, it was not possible to 

determine the rates of myocarditis in younger adults from the Israeli data that is available to 

date.66

To summarize the GRADE assessment for the Pfizer-BioNTech COVID-19 vaccine for persons

18 years of age and over who completed a COVID primary series 6 months ago or more, in 

terms of benefits beginning with the prevention of symptomatic laboratory-confirmed COVID, the 

available data indicate that the Pfizer-BioNTech booster dose induced an immune response 

non-inferior to those following Dose 2. Observational data suggest an increased protective 

effect against any SARS-CoV-2 infection. The evidence type was 4. For hospitalization due to 

COVID, the observational data suggest a protective effect against severe COVID and the 

evidence type also was 4. No other data were available on the important outcomes of death due 

to COVID or transmission of SARS-CoV-2 to infection.

To discuss the benefit/risk assessment by age, the NNV with a booster dose to prevent 1 

hospitalization over 6 months varies substantially by age. Over 19 times more individuals 18-29

years of age would need to be vaccinated to prevent 1 hospitalization compared to those 65 

years of age and over. The benefit/risk balance among the younger population variers by sex, 

the VE after the booster dose, rates of myocarditis, and incidence. As incidence declines, there 

will be more uncertainty around the balance of benefits and risks. To summarize the benefit/risk 

assessment, the risks of myocarditis after a third dose of mRNA vaccines are unknown. It is 

known that after the second dose, the risk varies by age and sex, so similar patterns may be 

seen after a booster dose. The benefit/risk balance is the most favorable for adults 65 years of 

age and overusing current estimates of VE. The benefit/risk balance among younger 

populations varies by sex, VE after the booster dose, rates of myocarditis, and incidence. In

addition, if COVID incidence increases, the benefits would increase. But as incidence declines,

there would be more uncertainty around this balance of benefits and risks.

Moving to the summary of benefits and harms by age and population, the data from the clinical 

trial are limited in size and age. The booster dose of the Pfizer-BioNTech COVID-19 vaccine 

increases the immune response in those who have completed a primary series approximately 6

months previously. Again, the individual balance of benefits and risks varies by age. The largest 

benefit of vaccination is in individuals 65 years of age and over. The benefits to the other ages 

are incrementally smaller given higher VE currently maintained from the primary series.

However, it is known that even within those age categories there is likely variation within the 

balance of benefits and risks given risk of exposure, medical conditions, and sex. The analysis 

of the benefits and risks also may be unable to account for other benefits. There may be a 

possible impact on rates of community transmission as well.

66 https://www.fda.gov/media/152205/download
ACIP Meeting Summary September 22-23, 2021

71

Values and acceptability were assessed in terms of whether people want a booster dose. In 

public surveys completed in August, 76% to 87% of vaccinated adults reported that they would 

get a booster dose if available. In one survey, this increased to 93% of adults if it was 

recommended by their primary care provider (PCP).

67 According to detailed data from an 

unpublished survey in which vaccinated respondents were asked if they would receive a booster 

dose, around two-thirds said they would get one soon as possible. Others said they would wait 

to see if it works or if it is safe. Only 2% of vaccinated respondents said that they would 

definitely not get a booster. When unvaccinated respondents were asked about boosters,

around one-third of unvaccinated respondents said that a recommendation for COVID-19

booster doses would make them less likely to get vaccinated at all. In this survey, individuals 

also were asked who they believe should be prioritized for early receipt of COVID-19 booster 

doses. Most individuals highlighted HCW, LTCF residents, and those 75 years of age and over. 

These individuals felt that essential workers, those age 65 to 74, and other countries should be 

prioritized for vaccines. Adults less than 65 years of age were the least prioritized group.

68 In 

summary, at least two-thirds of vaccinated adults are willing to receive a booster dose and

survey respondents prioritized older adults and HCW for booster doses, while younger adults 

were less prioritized.

Moving to feasibility and implementation, consideration was given to how booster doses would 

be implemented. Looking at completed primary vaccination series by week for those who 

completed the primary series 6 months or more, adults ≥65 years of age were prioritized for 

early vaccine doses. Overlaying those who would have completed the primary series 6 months 

and more, those who received their primary series prior to 3/19/21 would be eligible for a 

booster dose. This table shows the number of people who would be eligible in millions for a 

booster dose on September 27, 2021:

≥6 months after primary series

Age Group Pfizer-BioNTech Moderna Janssen/J&J Total

18-29 years old 2.0 1.5 0.3 3.9

30-49 years old 5.5 4.4 0.9 10.8

50-64 years old 5.3 4.4 1.2 11.0

65+ years old 13.6 12.9 0.8 27.4

Total 26.4 23.4 3.3 53.0

67 1) Axios Ipsos Poll. August 2, 2021; 2) Axios Ipsos Poll. August 30, 2021; 3) Marist Poll. September 3, 2021; 

https://maristpoll.marist.edu/polls/npr-pbs-newshour-marist-national-poll-covid-september-3-2021/; 4) Morning Consult Poll. 

August 25, 2021. https://morningconsult.com/2021/08/25/covid-booster-shot-poll/; 5) Reuters/Ipsos Poll. September 1, 2021. 

https://www.reuters.com/business/healthcare-pharmaceuticals/most-vaccinated-americans-want-covid-19-booster-shotsreutersipsos-poll-2021-09-01/

68 CDC/University of Iowa unpublished data, August 2021
ACIP Meeting Summary September 22-23, 2021

72

Of the total of 53 million individuals who would be eligible for a booster as of September 27, 

2021, over 27 million are 65 years of age and over. It is known that the jurisdictions have begun 

preparing for implementation of booster doses. Booster doses will be given in a variety of 

settings, including: pharmacies, provider offices, health departments, occupational clinics, and 

federal programs such as the LTCF Program. Over 70% of current COVID vaccine 

administration is occurring in pharmacies. Many jurisdictions are known to be experiencing a 

surge in cases of COVID-19, while continuing to engage in outreach for unvaccinated 

individuals to receive a primary series and beginning the fall and winter influenza campaigns.

There is known to be variation in what has been received as a primary series. There are 3

vaccines currently being administered in the US. For additional doses of mRNA vaccines in 

immunocompromised persons, the current recommendation states that an additional dose 

should be the same product as the primary series. If the product given for the first 2 doses is not 

available, the other products may be administered. However, the evidence reviewed by FDA 

only evaluated a booster dose of Pfizer-BioNTech vaccine after completion of a Pfizer vaccine. 

LTCF can arrange for on-site vaccination clinics or can help residents access vaccines in a local 

community. The federal LTCF program can help implement vaccination in these LTCF settings.

It is known that 8.1 million doses were administered during the original LTCF program from 

December 2020 through March 2021. Of those doses, 6.2 million (76%) were Pfizer-BioNTech

and 1.9 million (24%) were Moderna. In addition, those in LTCFs now may not be the same 

individuals who were there 6 months ago due to substantial turnover over time. Studies have 

previously demonstrated turnover of 30% per month for residents and 100% per year for staff. 

To highlight an issue that could impact implementation, the definition of “fully vaccinated” in the 

current CDC clinical considerations

69 state, “For public health purposes, immunocompromised 

persons who have completed a primary vaccine series (i.e., 2-dose mRNA vaccine series or a 

single dose of the Janssen vaccine) are considered fully vaccinated ≥2 weeks after completion 

of the primary series.” Based on current data, the definition of “fully vaccinated” would remain 

the same after recommendations for a booster dose. The “fully vaccinated ≥2 weeks or more 

after completion of the primary series” can be evaluated as additional information is learned 

over time. 

To summarize feasibility and implementation, 220 million doses of the Pfizer vaccine have been 

administered in the US to date, demonstrating that the vaccine is feasible to implement. Over 

2.25 million individuals already have received an additional dose. Over 27 million adults ≥65 

years of age completed their primary series 6 months ago and 50 million adults ≥18 years of 

age completed their primary series 6 months ago. Pharmacies are delivering the majority of 

COVID-19 vaccines currently. Recommendations that are clear and simple will facilitate 

implementation.

In terms of resource use or the cost associated with booster doses, all COVID vaccines, 

including booster doses, will be provided free of charge to the US population. However, health 

systems or health departments could incur costs for vaccination program planning and 

implementation. Fees for administration of COVID-19 vaccines recommended by the ACIP are 

reimbursable by insurance or other federal programs. The WG has expressed that costeffectiveness analyses will be important in the future when vaccine is not purchased and

distributed by the federal government.

69 https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html
ACIP Meeting Summary September 22-23, 2021

73

With respect to the equity consideration for booster doses, Hispanic or Latino, Black or African 

American, and AI/AN populations have been disproportionately affected by the COVID-19

pandemic. These populations experience higher rates of infection and mortality compared with 

the non-Hispanic White population and greater excess mortality, which is the percentage 

increase in the number of persons who have died relative to the expected number of deaths for 

a given place and time. In terms of annual excess death incidence rates for persons aged 25-64 

years by race and ethnicity in the US during the COVID-19 pandemic in 2020, AI/AN and Black 

populations had the highest annual excess mortality incidence rates.70 As of mid-September

2021, AI/AN and Black and Hispanic populations had the highest COVID-19-associated 

hospitalization rates compared to the overall population; whereas, White and Asian Pacific 

Islander populations had the lowest.

71

As of mid-September, AI/AN and Native Hawaiian or other Pacific Islanders and Asians have 

the highest percentage of those who have received at least 1 dose of vaccine, while the Black 

population has the lowest at 34%. There has been variation over time for the vaccination rates 

by race and ethnicity. AI/AN populations have consistently had the highest percentage among 

those who have received at least 1 dose of the COVID vaccine. Hispanic or Latino populations

started at a lower proportion, but has increased faster than other races over recent months.

72

Among VE platforms able to provide specific evidence for VE by race or ethnicity, no differences 

were noted. Overall VE against hospitalization among adults ≥50 years of age was 89% (95% 

CI: 87-91%), for Black individuals was 86% (95% CI: 75-92%), and for Hispanic individuals was 

90% (95% CI: 85-93%). VE against hospitalization among VA centers was 86% (95% CI: 77-

93%) for Black individuals and 88% (95% CI: 77-94%) for White individuals.

73 To summarize 

equity, COVID-19 disease and COVID-19 vaccination varies by socioeconomic and 

sociodemographic groups. However, VE does not vary by race and ethnicity. While the equity

gap in vaccines administered by race is closing, disparities were more pronounced this spring,

which would be individuals who would be 6 months or more after their second dose.

In terms of the WG’s interpretation, the WG continues to emphasize that the top priority should 

be continued vaccination of unvaccinated individuals. In addition, jurisdictions have a variety of 

vaccination and disease control priorities such as surges in COVID-19 cases and delivery of 

primary COVID-19 vaccine and influenza vaccine. The WG discussed that the balance of 

benefits and risks vary by age. Adults ≥65 years have the clearest benefit/risk. The benefit to 

other age groups is incrementally smaller, given the high effectiveness maintained from the 

primary series. The WG discussed the goal of the booster program to be prevention of severe 

disease. They also recognized that other considerations are important, such as maintaining

workforce and healthcare capacity, prevention of transmission, and the individual benefit/risk 

balance.

70 Rossen LM, Ahmad FB, Anderson RN, et al. Disparities in Excess Mortality Associated with COVID-19 — United States, 2020. 

MMWR Morb Mortal Wkly Rep 2021;70:1114–1119. DOI: http://dx.doi.org/10.15585/mmwr.mm7033a2

71 CDC. https://covid.cdc.gov/covid-data-tracker/#covidnet-hospitalization-network. Accessed September 21, 2021

72 CDC. https://covid.cdc.gov/covid-data-tracker/#vaccination-demographics-trends as of September 20, 2021, and US Census 

Bureau National Population Estimates

73 M Thompson et al. NEJM https://www.nejm.org/doi/pdf/10.1056/NEJMoa2110362?articleTools=tru
ACIP Meeting Summary September 22-23, 2021

74

Interim Clinical Considerations for Pfizer-BioNTech COVID-19 Vaccine Booster Doses

Dr. Kathleen Dooling (CDC/NCIRD) reviewed the existing interim clinical considerations for the 

use of Pfizer-BioNTech COVID-19, as well as the proposed groups for whom a booster may be 

considered. For public health purposes, people who have completed a primary series of a 

vaccine (i.e., 2-dose mRNA vaccine series or a single dose of the Janssen vaccine) are 

considered fully vaccinated ≥2 weeks after completion of the primary series. This definition 

applies to all people, including those who receive an additional dose as recommended for 

moderate to severely immunocompromised people and those who may receive a booster dose 

in the future.74

Pfizer-BioNTech COVID vaccine (BTN162b2) is administered as a 0.3 ml intramuscular 

injection. It should be noted that this is the exact same formulation, dose, and route as has been 

previously authorized and approved for the Pfizer COVID vaccine. With regard to the timing of a 

booster dose, a single dose should be given at least 6 months or more after completion of the 

primary series. It is important to note that immunity wanes gradually over time. Therefore, it is 

not necessary for the booster dose to be given exactly at 6 months. In fact, a booster dose may 

be given at a period of 6 months or more after the primary series. In terms of co-administration,

Pfizer-BioNTech COVID vaccine booster may be given with other vaccines without regard to 

timing. This includes simultaneous administration of COVID-19 with a Pfizer vaccine and other

vaccines on the same day.

To review the groups at risk for severe COVID-19 or SARS-CoV-2 infection even after 

vaccination with a primary series, increasing age is a strong risk factor for severe COVID. 

People ≥ 65 years who are fully vaccinated are at an increased risk for severe COVID-19, 

including hospitalization and death, compared to younger fully vaccinated people. In addition,

waning of COVID-19 VE against severe disease has been observed in people ≥ 65 years of age 

and older. While most residents of LTCFs facilities are over 65 years of age, this is a risk-based 

group and would include any residents 18 years of age and older. There is likely an increased 

risk of severe COVID-19 (including hospitalization and death) among fully vaccinated residents 

compared to fully vaccinated people who are living independently. Waning of COVID-19 vaccine 

protection against infection and has been observed in LTCF residents. In addition, congregate

living settings are associated with increased risk for COVID-19.

The next group is risk-based by occupation or settings. This group includes people 18 years of 

age and older who are fully vaccinated and may be at increased risk for SARS-CoV-2 infection 

due to frequent exposure in their occupation or other settings. Moreover, an individual who is 

absent from their occupations due to SARS-CoV-2 infection may hinder societal functions. 

Examples include but are certainly not limited to essential frontline and non-frontline workers,75

paid and unpaid caregivers of frail or immunocompromised persons, paid and unpaid workers 

who interact within less than 6 feet of others, and people who live in congregate settings (e.g., 

homeless shelters or correctional facilities).

74 nocompromised people and those who receive a booster dose https://www.cdc.gov/coronavirus/201 9-ncov/vaccines/fullyvaccinated.html

75 https://www.cisa.gov/publication/guidance-essential-critical-infrastructure-workforce
ACIP Meeting Summary September 22-23, 2021

75

The final risk-based group is people 18 years of age and older with underlying medical 

conditions and fully vaccinated people with underlying medical conditions who may be at risk for 

severe COVID-19 if they become infected with SARS-CoV-2. Examples of underlying medical 

conditions associated with severe COVID include, but are not limited to: cancer, 

cerebrovascular disease, chronic kidney disease (CKD), chronic obstructive pulmonary disease 

(COPD), diabetes mellitus type 1 and type 2, heart conditions (such as heart failure, coronary 

artery disease, or cardiomyopathies), obesity (BMI ≥30 kg/m2), pregnancy and recent 

pregnancy, and current/former smoking.

76

Looking at the factors for considerations for the individual level assessment of benefits and risks

of a COVID-19 vaccine booster dose, the potential benefits to an individual are that a booster 

may confer reduced risk of infection and severe disease. The strongest evidence for the benefit 

of reduced risk of severe disease is in older adults. The VE of an mRNA primary series remains 

high in younger age groups. A booster dose of COVID vaccine may confer reduced risk of 

SARS–CoV-2 infection. Waning of vaccine protection via a combination of factors such as time

since vaccination and Delta variant has been observed in most age groups. It is important to 

note that infections may be symptomatic or asymptomatic. A booster may reduce work absence 

and preserve the capacity of important sectors. Stated another way, prevention of infection may 

protect healthcare capacity and other essential services for the COVID-19 response and 

maintain the overall functioning of society.

To review the potential risks to an individual that should be considered, myocarditis and 

myopericarditis are very rare but may occur following an mRNA vaccination. It is more common 

in younger ages, particularly males younger than 30 years old. Most patients with myocarditis 

have been hospitalized for short periods, the majority of whom achieve resolution of their acute 

symptoms. The rate of myocarditis following a booster dose is not yet known. Anaphylaxis, 

although very rare, may occur following a COVID mRNA vaccination. The rate of anaphylaxis 

following a booster dose is not yet known. Reactogenicity, including transient local and systemic 

symptoms, are common following mRNA vaccines. The third dose of Pfizer-BioNTech COVID19 vaccine appears to have similar reactogenicity as the second dose.

When assessing the benefits and risks, individuals should consider their own risk of SARS-CoV2 exposure. For example, individuals can assess their risk of excessive exposure in 

occupational, living, and transportation settings. Consideration should be given to their ability, 

for example, to consistently wear a mask, maintain social distance, and other mitigation 

measures. In addition, consideration should be given to rates of SAR-CoV-2 infection in the 

community. Individuals also can consider their risk of developing severe COVID-19 if infected. 

This may be influenced by underlying medical conditions, particularly if those conditions are not 

well-controlled. Individuals also can consider their personal circumstances, such as living with or 

caring for a frail or immunocompromised person or the consequences of the inability to meet 

personal or occupational obligations due to SARS-CoV-2 infection.

Consideration also must be given to contraindications, precautions, and other AEs following 

immunization. The contraindications and precautions would be the same for booster doses as 

for the primary series of a Pfizer COVID-19 vaccine. A contraindication may include severe 

allergic reaction (e.g., anaphylaxis) after a previous dose or to a component of the Pfizer 

BioNTech COVID-19 vaccine, or an immediate allergic reaction of any severity to a previous 

dose or known diagnosed allergy to a component of the vaccine. Polysorbate allergy is a 

precaution to mRNA COVID-19 vaccinations. If myocarditis or myopericarditis occurs following a 

76 https://www.cdc.gov/coronavirus/2019-ncov/hcp/clinical-care/underlyingconditions.html
ACIP Meeting Summary September 22-23, 2021

76

dose of mRNA vaccine, it is recommended to defer a subsequent dose. People who choose to 

receive a subsequent dose should wait until myocarditis or myopericarditis has completely 

resolved. It should be noted that the aforementioned conditions, certainly the ones that result in 

contraindication or precaution, are extremely rare. Many resources can be found on the “Clinical 

Considerations” section of the CDC website. Those include information about anaphylaxis and 

its management in the vaccine setting.

77

Types of Recommendation ACIP Could Make

Dr. Sara Oliver (CDC/NCIRD) reviewed the types of recommendations ACIP can make, as well 

as what this recommendation would mean for the balance of benefits and risks. The 

recommendation options are:

❑ ACIP does not recommend the intervention: This would occur when it is felt that across 

the population, the risks outweigh the benefits. 

❑ ACIP recommends the intervention: This would be used when the benefits clearly 

outweigh the risks in the population. 

❑ ACIP recommends the intervention for individuals based on assessment of benefits 

and risks: This could be used when there is diversity of the benefits and risks within a 

population. This type of vote could allow for flexibility across the population when there is 

more variation around the balance of benefits and risks.

The WG proposed two policy options for ACIP’s consideration shown in the following tables, 

with some of the pros and cons identified for each:

Policy Question #1:

Should adults ≥65 years of age and LTCF residents receive a Pfizer-BioNTech COVID-19 

vaccine booster dose?

PROS CONS

• Highest risk of severe disease

• Largest impact in waning VE against severe 

• disease

• Prioritized for early doses of COVID-19 

vaccines (longer duration since primary series)

• Age cut-off may not represent continuum of risk

77 https://www.cdc.gov/vaccines/covid-19/downloads/IntermConsid-Anaphylaxis-covid19-vaccine-sites.pdf 
ACIP Meeting Summary September 22-23, 2021

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Policy Question #2:

Should adults 18–64 years of age at risk for severe COVID-19 due to underlying medical 

conditions or at risk of SARS-CoV-2 exposure due to occupation/setting receive a PfizerBioNTech COVID-19 vaccine booster dose?

Type of 

Recommendation

PROS CONS

Standard 

recommendation

• Simple

• Reduces barriers for 

individuals who may have 

increased risk of disease

• Reduction in infection could 

reduce work absenteeism

• Not strong evidence of 

increased risk of 

hospitalization or death in all 

individuals

• Balance of benefits and risks 

likely varies

• Large number of people 

initially eligible (>50 million)

Recommended for 

individuals based on 

assessment of benefits 

and risks

• Reduces barriers for 

individuals who may have 

increased risk of disease

• Reduction in infection could 

reduce work absenteeism

• Reflects uncertainty in current 

balance of benefits and risks 

in this population

• Large number of people 

initially eligible (>50 million)

• More complicated to 

implement

Discussion Points

Dr. Poehling emphasized that ACIP would consider persons who have completed the primary 

series as being fully vaccinated. This is an important point in that it gives people an opportunity, 

but not a requirement. She indicated her support for Policy #1 as it was clear from the data that 

the risk of hospitalization was increasing among those ≥65 years of age and LTCF residents, 

and that the benefits outweigh the risks. In terms of Policy #2, she thinks a lot about the 

immunocompromised such as children under 12 years of age for whom there is not yet a 

vaccine and adults in the full spectrum. It appeared to her that immunocompromised people and 

their caregivers would be included under this setting. For instance, the caregiver of a child who 

is medical fragile or immunocompromised would be included. In terms of the two 

recommendations, it seemed to her that the intent was to allow availability without mandating.

Dr. Oliver confirmed that this would be correct. Settings were drawn to be broad and include 

settings in which someone is a caregiver for an immunocompromised or frail person.

Dr. Kotton emphasized that for Policy Question #1, making the age cutoff of ≥65 years of age

creates an equity issue because this age is not equal across all racial groups. Different 

outcomes have been observed at different ages across different races with COVID, so this 

proposed cutoff may not meet the intent for trying to ensure as much equity as possible. She 

also suggested that perhaps Policy Question #2 should be divided into two separate questions 

in that it may hard to reach agreement on the two areas of underlying medical conditions and 

occupation/setting.
ACIP Meeting Summary September 22-23, 2021

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Dr. Cohn reminded everyone that these policy questions are based on the language that were in 

the conditions of use from the FDA authorization from the previous evening. Therefore, they did 

not have flexibility in terms of Policy Question #1 to shift the age group from ≥65 years of age. 

Policy Question #2 certainly could be split into a discussion on underlying medical conditions 

and exposure to occupation/setting. That question did allow for an opportunity to shift some of 

the ages around. For instance, individuals at a lower age who are at severe risk for disease 

could have a full recommendation as compared to the more individual level recommendation for 

other types of groups. Therefore, one way to address the equity issue that could not be 

addressed in Policy Question #1 would be to shift things around in Policy Question #1.

Dr. Talbot pointed out there are data showing some decline in VE for the Pfizer BioNTech 

COVID-19 vaccine, and there are reasons for that, including the shorter interval between Doses 

1 and 2 compared to the other mRNA vaccine. To her, the most important policy question 

pertains to the Janssen/J&J vaccine. That vaccine has much lower VE and she worried that they 

were getting distracted by the question of the Pfizer BioNTech booster when they really need to 

figure out what to do in the pandemic. Along the lines of fighting the continued pandemic, it is 

not because people got 2 doses—it is because people are unvaccinated. While giving booster 

doses to already vaccinated people may move the needle a little bit, the fact is that this is now a 

pandemic of the unvaccinated and the hospitals are full of people who are not vaccinated. Care 

is being declined to people who deserve care because hospitals are full of unvaccinated 

COVID-positive patients. Giving boosters to people is not really the answer to this pandemic.

Dr. Ault noted that as far as knowledge gaps for Policy Question #2, there are pregnant women 

and those who have underlying medical conditions who are at risk for worsening disease. There 

also are HCW who are skewed toward younger and female individuals, so this means hundreds 

of thousands of pregnant and lactating HCW at any one time. There are complicated questions 

to answer for people who fall within this category, and numerous pregnant women have 

received zero doses. That also will have to be addressed somehow.

Dr. Sanchez agreed that they must remember that they are talking about booster doses for 

individuals who already have agreed to receive a vaccine and to be fully vaccinated, so he 

thought the equity issues were somewhat different. That said, he agreed with Policy Question 

#1 and had some issues with Policy Question #2 in that it should be further separated out as 

mentioned by others. He did not think Policy Question #2 helped parents or others who are 

caring for immunocompromised persons at home if the parents/caregivers are less than 65 

years of age and otherwise healthy. While this could be read into the setting, it is not explicitly 

stated that healthy parents/caregivers less than 65 years of age may need to be vaccinated for 

the sake of a fragile child. The FDA states that, “Individuals 18 through 64 years of age whose 

frequent institutional or occupational exposure to SARS-CoV-2 puts them at high risk of serious 

complications of COVID-19 including severe COVID-19.” Policy Question #2 seemed to be 

expanding that, which would be fine if allowed. However, he thought that was somewhat 

different in terms of HCW and younger people who may not be at high risk of severe disease.

Dr. Brooks agreed with Policy Question #1. He emphasized that the evidence for African 

Americans shows that their increased risk for death and hospitalization increases dramatically at 

age 50. It is likely that a lot of that is related to underlying medical conditions, so adoption of

these policy questions in any fashion would mitigate some of that. He reminded everyone that it 

was important to remember that these recommendations were only for those who received the 

full series of the Pfizer vaccine. In addition, a lot of this would be based on the availability of 

vaccine. About 76% to 93% of people who had two doses expressed a willingness to get a 

booster, so those who want a booster should be able to get it. Importantly, no major risks were 
ACIP Meeting Summary September 22-23, 2021

79

identified either. One concern was that one-third of the unvaccinated said that a booster would 

make them less likely to get vaccinated, so a recommendation for a booster might reduce the 

ability to get the unvaccinated to get vaccinated. On balance, he thought that Policy Question #2 

and a flexible recommendation would have a lot of positivity, but if done as a full 

recommendation it might be perceived as a mandate and that could be somewhat problematic.

Dr. Oliver noted that receipt was broken out by primary series in the presentation. With 6 

months or more after the primary series, 26 million received Pfizer and 13 million of those are 65 

years of age and over.

Dr. Cohn noted that their FDA colleagues could answer specific questions about the EUA. The 

issue of people who are living in the home of immunocompromised persons, the language in the 

FDA EUA states “occupational or institutional risk.” The proposed ACIP language is a little 

different from the FDA, but is believed to have the same intent. From that perspective, she 

asked the ACIP members to not worry about how this discussion aligned exactly with the intent 

of the FDA EUA. CDC will make sure that they are within the conditions of use before issuing 

any final recommendations. She noted that the questions had now been separated into 3. While 

they could split the ages of 18–64 years to have different recommendations for different ages, 

but they certainly want to try to keep the recommendations reasonable from a simplicity 

perspective.

Ms. Bahta noted that there was nothing in the clinical guidance to address the mixing of vaccine 

products. She also expressed concern that the policy questions sent a message that the primary 

series was not enough and people would need more. She also agreed that boosters would not 

end the pandemic, and pointed out that many of those who did get vaccinated abandoned other 

mitigation measures. With unvaccinated individuals becoming very ill and vaccinated people 

were also getting sick, which reduced the confidence people have in the vaccine. With that in 

mind, she supported Policy Question #1 and thought Policy Question #2 should be adjusted to 

include a more equitable consideration. They must ensure that they talk about this as only one 

measure in the midst of a pandemic and explain what everyone needs to do whether they are 

vaccinated or unvaccinated. In terms of age group, she thought 50-64 years would be suitable 

because it is known that there is a large group of individuals in that age range who have similar 

risks. She emphasized that they should not imply that they are not protected, because most 

people are.

Dr. Long emphasized that it is imperative to protect people from death and hospitalizations. She 

agreed that people of different races and ethnicities age differently, but there were absolutely no 

data to suggest that there was a diminution of vaccine protection or antibody responses based 

on race or ethnicity. Although there may be more severe disease in people under 65 years of 

age, she had not seen the data in breakthrough disease to suggest that this is the case—at 

least to any extent. She also assumed that in addition to LTCF as done previously, Policy 

Question #1 would apply to everyone in congregate living. She wondered whether Policy 

Question #1 would be a preference for everyone who received Pfizer vaccine, but an allowance 

for those who received Moderna or Janssen/J&J. She supported Policy Question #1, but 

thought it would be anathema to preclude people from getting Pfizer if they had a different 

primary series. For Policy Question #2, there did not seem to be evidence showing that 

underlying medical conditions reduce protection. There did not appear to be substantial waning 

in the younger age groups. Risk for severe disease did not seem to extend from caretakers to 

the people they take care of. Policy Question #3 seemed rather thorny to her.
ACIP Meeting Summary September 22-23, 2021

80

Dr. Daley expressed strong support for a full standard recommendation for Policy Question #1. 

His interpretation of Policy Question #2 differed from Dr. Long’s and he fully supported a full 

recommendation for those 50-64 years of age with underlying medical conditions for several 

reasons. First, that is a group who has underlying medical conditions and some 

immunosenescence. Second, the risk of myocarditis did not appear to be elevated in this group. 

Therefore, the benefits for booster in that group are likely to outweigh any risks. Third, that 

approach may achieve greater equity as mentioned by others. He was contacted by a colleague 

who reached out with the observation that many in the AI/AN population do not reach the age of 

65 years due to underlying medical conditions and the effects of social determinants of health 

(SDOH). He preferred to hear more about those 18-49 years of age with underlying medical 

conditions and what type of recommendation would be most appropriate for that group. He 

tabled his comments for Option #3 for later.

Dr. Fink walked the ACIP through the authorized population and the FDA’s rationale for that in 

order to help answer some of the questions raised. The statutory requirements for EUA would 

require FDA to find that a booster dose may be effective to prevent a serious disease or 

condition. FDA also has to evaluate the benefit of a booster dose in relationship to whatever 

benefit exists from the primary series, because anyone being considered for a booster dose will 

have received a primary series. They heard evidence during the VRBPAC presentation the 

previous Friday that FDA thought clearly enough demonstrated a risk of hospitalization and 

severe COVID (e.g., a serious condition) among individuals 65 years of age and older who had 

passed some time since their primary series. That was the rationale for including that age group. 

They did not see evidence presented to support that younger age groups in the general 

population were at increased risk. In fact, they also did not see evidence to support that specific 

subgroups within the younger population were being hospitalized at higher rates. However, they 

did consider that individuals who at baseline were at increased risk of severe outcomes from 

COVID-19 would reasonably be expected to be at higher risk of severe outcomes and 

hospitalization even following the primary series with protective immunity. This was the rationale 

for including in the authorized population individuals 18-64 years of age at high risk of severe 

COVID, whether that risk is due to underlying medical conditions or some other factor. 

Regarding the third component of the authorized populations, FDA also considered that frequent 

and unavoidable exposure to SARS-CoV-2 would increase the risk of symptomatic COVID that 

would carry increased risk of serious complications of COVID (e.g., severe presentation of 

COVID; long COVID). It was with this thinking in mind and considering groups that have both 

frequent and unavoidable exposure to SARS-CoV-2 that the FDA decided to authorize the 

booster dose in institutional or occupational settings. This construction differentiates those 

groups who have frequent and unavoidable exposure to the virus in institutional and 

occupational settings from the general population. The VRBPAC did not find that the totality of 

evidence supported the use of a booster dose in the general population of younger adults 16-64 

years of age.

Dr. Lee thanked Dr. Fink for clarifying FDA’s intent and pointed out that ACIP certainly wants to 

stay within the intent of the regulatory decision that FDA has made, so they would continue to 

discuss this robustly. She asked him to comment on the question that arose regarding the timing 

of availability of a booster dose of the Janssen/J&J vaccine and the gap that might emerge, 

recognizing that there had not been a submission.
ACIP Meeting Summary September 22-23, 2021

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Dr. Fink indicated that there were no data available to inform the interchangeability of authorized 

COVID-19 vaccines, either for completion of a primary series or for use of a booster dose. 

Consequently, the Pfizer-BioNTech COVID vaccine was authorized for use as a booster dose 

among certain individuals in the authorized population who completed the primary series of 

Pfizer-BioNTech COVID vaccine. FDA received Moderna’s EUA application for an amendment 

for a Moderna COVID vaccine booster dose, which is under review and they are working 

diligently to get that completed. He is also very sensitive to and understands the desire for 

flexibility regarding use of COVID vaccines, as well was the concern about individuals who 

received the Janssen/J&J vaccine. Data show that the Janssen/J&J vaccine continues to 

provide very good protection against severe outcomes, including hospitalization and death. 

Although notably its protection is not at the same level as the primary series of the mRNA 

vaccines. As a physician, he is frustrated with the lack of data that would allow for a regulatory 

allowance and for evidence-based recommendations from the ACIP for evidence-based 

practice. FDA is working diligently with vaccine manufacturers and its other partners the federal 

government, including the NIH, to arrive at a solution expediently to address the situation and 

provide a solution that will comply with legal requirements. 

Dr. Marks added that FDA understands the relative urgency of trying to have a solution for 

anyone who has been vaccinated with any of the authorized or approved vaccines. 

Unfortunately, they were not able to provide an exact timeline. However, they will proceed with 

all due urgency to try to get there as rapidly as possible working with the various vaccine 

sponsors and all of the available data to make a science-based decision so that there is 

something based on evidence to bring forward.

Dr. Lee emphasized that ACIP appreciates that everyone is working toward the intent of trying 

to protect the American public, and pointed out that the concerns raised by the committee were 

really ones of equity and ensuring that the FDA, CDC, all federal colleagues, clinicians on the 

frontline, and public health colleagues can make sure that they are working to achieve equity in 

all aspects of vaccine policy.

Dr. Bell observed that there has been some confusion and lack of clarity of about what the FDA, 

VEBPAC, CDC, and ACIP do. There is now an EUA from the FDA for giving a Pfizer/BioNTech 

booster to people who received a primary series under the EUA category, which means that this 

booster is available to people in the US. ACIP needs to consider the totality of evidence and 

think about what makes the most sense using the tools available, as Dr. Walensky said, to 

protect as many people as possible. In addition, ACIP must consider how to operationalize this 

considering other elements, such as feasibility. She stressed that the question before them was 

very narrow and that there were many moving parts, competing priorities, the issue that this 

recommendation is only for people who received a Pfizer/BioNTech primary series, potential 

vaccination authorization upcoming for children, et cetera. She urged committee members not to 

get stuck on trying to definitively answer a question and come up with policies now in the midst 

of all of the moving parts and remembering, as Dr. Talbot said, if they really want to move the 

needle with this pandemic, more people must be vaccinated with the primary series. That should 

be the focus of the public health infrastructure in her opinion. Given all of that, putting aside 

Policy Question #1, and since it appeared that there was no evidence of waning VE among 

people younger than 65 years of age with underlying medical conditions, she was concerned 

that any inconsistency might cause more problems than anticipated. There was nothing to 

preclude anyone with an underlying medical condition from getting a booster if they had a 

primary series with Pfizer/BioNTech. Therefore, she did not have a huge amount of enthusiasm 

for ACIP making a recommendation with no evidence to boost VE in some populations above 

that of others. In terms of Policy Question #3, she thought there was ample evidence that 
ACIP Meeting Summary September 22-23, 2021

82

people such as HCWs do not have repeated exposure in their workplace. They are using 

personal protective equipment (PPE) as they should and are following other policies within the 

healthcare setting. There is a lot of evidence to suggest that HCW who become infected 

become infected because of exposures in the community. Therefore, she did not believe the 

third statement to be scientifically correct and would say the same about teachers. As she 

mentioned the previous day, she thought a case could be made for vaccinating HCWs to reduce 

the incidence of infections that they get because of exposures in the community and to reduce 

absenteeism among vaccinated HCW. Otherwise, she was not ecstatic about voting for a 

booster dose in a population based on a rationale that she did not think was actually supported 

by evidence.

Dr. Loehr indicated that he was in favor of Policy Question #1, was against the standard 

recommendation for Policy Questions #2 and #3, but might consider a judgment call on those 

two. He felt that the goal was to decrease hospitalizations and that vaccinations would do that, 

but that they were getting too much ahead of themselves and placing too much hope on the line 

with boosters. He calculated the numbers and determined that even if boosters were given to all 

13 million people over 65 years of age who have had the Pfizer/BioNTech primary series, that 

might result in 200 fewer hospitalizations a day. While that is a lot, there are 10,000 

hospitalizations a day at this point, it is not that much compared to the goals of getting the 

unvaccinated and children vaccinated. Nevertheless, he emphasized that they should not let the 

perfect get in the way of the good. If they could do a little bit by giving boosters to those over 65 

years of age, he favored that. Regarding Policy Questions #2 and #3, it was clear from public 

comments and his own anecdotal experience that people want boosters. He agreed that there

are no data, so he was hesitant to make a standard recommendation. However, he could see 

making a recommendation based on clinical judgment.

Dr. Cohn stressed that this was an unusual situation that was not the typical vaccine policy 

development framework in that there were not public and private vaccines. All of the COVID 

vaccine had been purchased by the US government (USG). Because of that key difference, the 

FDA EUA alone is not sufficient to allow for access to population that are also covered by some 

sort of ACIP recommendation, be it a standard or more individual decision-making focused 

recommendation. For instance, a vote of “yes” to the first question and “no” to 2 and 3 would 

mean that only those 65 years of age and above would be eligible to get a booster dose at this 

time. She was hearing from everyone the very important and clear point that the public health 

goal right now should be to get people vaccinated who are unvaccinated, and recognized that 

there were multiple competing priorities at the public health level. In pre-COVID days, the way 

that ACIP framed a permissive, individual, or shared clinical decision-making recommendation 

was to think about it as a public health program for a full recommendation. A permissive 

recommendation for Policy Questions #2 and #3 would not require the same public health focus 

as a full recommendation. She imagined that individuals in those areas would get their booster 

doses if they chose to do that in pharmacies and other places that would not have a significant 

impact on all of the competing priorities of public health. While clearly this would have some 

impact on public health so she did not want to overstate that, the standard recommendation 

would be the goals of public health at this time, which is a primary series for all individuals 12 

years of age and older, a booster dose for all individuals 65 years and older if they voted “yes” 

to Policy Question #1, and the additional dose for immunocompromised persons.
ACIP Meeting Summary September 22-23, 2021

83

Dr. Cineas agreed with others that the top priority was to vaccinate the unvaccinated and that 

any recommendations should not detract from that priority and goal. For Policy Question #2, she 

thought that the language should be kept as simple and easy to implement for providers as 

possible, while allowing for some shared decision-making and discretion and flexibility for 

providers to provide the additional dose.

Dr. Sanchez agreed with Dr. Bell’s comments. He also asked whether pregnancy would be 

included in underlying medical conditions in Policy Question #2. His expressed concern that 

Policy Question #3 did not explicitly include vaccinating otherwise healthy individuals who 

themselves could become infected who are caring from someone at home who could not be 

vaccinated. While he knew they were addressing just the Pfizer vaccine, they could not continue 

to ignore the Janssen/J&J product and the individuals who received it. There are data from 

Europe with heterologous dosing with the adenovirus vector with the AstraZeneca (AZ) vaccine 

and mRNA vaccine that showed good boosting.

Ms. McNally asked CDC to comment on Policy Questions #2 and #3 in terms of 

communications and education materials for providers on the needs assessment, particularly as 

it relates to Question #3.

Dr. Cohn responded that there absolutely would be communications and education materials in 

the same way that CDC has provided these for individuals to help understand which vaccine 

may be best for them for the primary series, given the differences between the vaccine. There 

would be materials for HCP, public health, and the public to support this decision-making. The 

presentation that Dr. Dooling laid out would form the basis of some of those considerations if 

ACIP decided to make these recommendations.

In terms of Policy Question #2, Dr. Poehling agreed that VE remained robust when looking at 

the overall population with high risk conditions. While that is really good news, it is known from 

clinical experience that there are persons with high risk medical conditions who are very fragile 

and in whom the most minor cold can cause them to have significant disease that leads to 

hospitalization. She was struggling about how to make sure that those who are the most 

medically fragile and younger than 50 to 64 years of age still have access.

It was not clear to Dr. Long how later in the afternoon ACIP was going to tell people 65 years 

and older that they are at risk for severe disease and death, but that only half of them can 

protect themselves right now since only those who received the Pfizer primary series would be 

eligible for the Pfizer booster. It might be the right thing to do, but she might vote against it 

because it did not sound like a good public health policy. Pregnant women are at an age where

they have had robust responses to these vaccines and there is no evidence that they have 

substantial waning, so she would not include pregnant women in the booster recommendation 

at this time. She did not like the shared decision-making. Individualized decision-making would 

mean that people of education, wealth, and ability would go to a pharmacy or provider to get a 

dose without significant need. The FDA said, “If you were originally at risk for severe disease 

before you got vaccinated . . .” where she would say, “If you are significantly at risk for X and 

you are at risk for waning, the data are incomplete but ACIP thinks the benefits now would 

outweigh the risks.”

Dr. Eckert (ACOG) reported that the American College of Obstetricians and Gynecologists

(ACOG) had a call on September 20th during which the general consensus was that they feel 

positive about boosters. At the same time, they recognized that many of the initial pregnant 

individuals who were vaccinated were HCW and were in the first round. They may have been 
ACIP Meeting Summary September 22-23, 2021

84

delivered by now, so it could be somewhat time sensitive in terms of wondering who should and 

should not get boosters depending upon whether they are postpartum or lactating. While it is a 

complicated question, the general feeling was that given the severe disease and the fact that 

many of the pregnant individuals were in the earliest wave of vaccinees, that ACOG favors 

consideration of boosters.

Referring to Slide 12 of Dr. Oliver’s presentation showing the age-adjusted weekly COVID-19 

hospitalization rates, Dr. Lee noted that vaccinated versus unvaccinated for people 50 to 64 

years of age was 22 times higher compared to 13 times higher for people 65 years of age and 

older. However, the baseline rates of hospitalization were higher in the 50 to 64 year olds likely 

due to additional medical conditions.

Dr. Duchin (NACCHO) highlighted the equity issue illustrated in their own COVID-NET 

hospitalization rates where hospitalization rates among 50 to 64 year olds non-Hispanic, AI/AN, 

Black, and Hispanic or Latino people are higher than those among non-Hispanic whites and 

Asian and Pacific Islanders for 65 years of age and older. In the context of the third dose for 

immunocompromised persons there is clinical consideration language that set a rather high bar 

for defining who is immunocompromised. If they were going to consider a recommendation for 

people with underlying medical conditions, he encouraged ACIP to be clear about what is 

considered to be an immunocompromising condition. From the local public health perspective, 

despite the wicked complexity of this problem, simplicity is needed in the guidance for 

implementation success.

Ms. Howell (AIM) echoed the need for simplicity, including allowing people to self-report 

underlying conditions, go to large vaccination clinics, and not require proof or a prescription if 

Policy Question #2 was chosen. While they need to get more unvaccinated people vaccinated, 

there are many local areas in which a large proportion of the population is unvaccinated and 

there is a struggle with HCW infrastructure. Policy Question #3 could significantly assist with 

HCW infrastructure in areas that have large numbers of unvaccinated people and are 

experiencing outbreaks.

Dr. Goldman (ACP) expressed concern with these policy options because it was not clear to him 

that there was overwhelming evidence to recommend them compared to the great benefits of 

the primary series. This is a disease of the unvaccinated. From a boots-on-the ground 

perspective, he was concerned about the unintended consequences of Policy Questions #2 and 

#3 in that they may be completely irrelevant and superfluous if implemented. As soon as the 

Biden Administration advised that boosters would be a guarantee, he had patients who already 

got a booster dose without anyone asking why. Pharmacies and other vaccinators were giving it 

to patients without any reason whatsoever. From an equity standpoint, if this is put in place and 

some type of certification is required from a physician, patients who have diseases who cannot 

get into physicians because they are already in a health disparity situation to get a form signed 

to get a vaccine will not get the booster. If no proof is required, people will get vaccines without 

any reason and may misrepresent underlying conditions just to get a booster. For those 

reasons, he thought Policy Options #2 and #3 were fraught with peril and would create 

inequities and problems with implementation.

Dr. Shah (ASTHO) indicated that over the past few weeks, ASTHO has had a chance to speak 

with state health officials across the country in connection with boosters and the rollout, and two 

prevailing themes emerged. The first pertained to Policy Question #1 in terms of some 

permissive allowance for use of a mix and match strategy, particularly in LTCF. Boosters will be 

peaking around the same time that various states and vaccination forces will be asked and 
ACIP Meeting Summary September 22-23, 2021

85

pressed into service to provide first doses for children 5 to 11 years of age, to say nothing of 

influenza shots and other healthcare needs. Having to go back to a health facility or LTCF in a 

few weeks to pick up those who received Moderna will pose a significant operational challenge. 

He recognized that as Dr. Fink and others pointed out, there are not definitive RCT data on the 

efficacy of mixing and matching. State health officials requested that as ACIP has done with 

respect to severely immunocompromised people, making an allowance for a preference for the 

same vaccine, but if not possible, to allow the mix and match approach. There is good reason to 

believe that the mix and match strategy would be applicable. The second observation from state 

health officials was a request for extreme clarity, particularly on Policy Questions #2 and #3. 

Though he understood it on the screen before them, the language in practice would leave open 

a lot of questions. For example, the US CDC has 4 tiers for the risk of COVID for underlying 

medical conditions. It was not clear whether it would be all 4 of those tiers or only certain ones 

of them. If it would be all 4 tiers, it would include those who are overweight which is about 73% 

of the population. If the intent is for boosters to be somewhat narrowly construed in only those 

18 to 64, if all 4 tiers, soon they would get to the point where overweight + coronary artery 

disease + hypertension would mean that Policy Question #2 would encompass most of the 

population. Similarly, clarity around Policy Question #3 with respect to which occupations and 

which settings would help avoid the patchwork of different states taking different policy 

approaches as occurred earlier with respect to the primary series.

Dr. Maldonado (AAP) said that in terms of equity, the implication was the risk for underlying

medical conditions among under-represented minorities. Frankly, the vast majority of data 

pertain to frontline workers who are not HCW but who work in settings that put them at risk 

where they may not be protected by PPE and other practices available in healthcare settings, 

and who live in communities of high risk would be over-represented in high risk groups. It is 

known that household density, living conditions, et cetera for these individuals are already a risk. 

It is clearly not a biological driver for under-represented minorities. It is really about SDOH. This 

is driving the pandemic overall in addition to unvaccinated people. Vaccinated people in high 

risk groups who will not have access to boosters is going to further the inequities in those 

populations. Therefore, she made a case for considering under-represented minority groups 

who are primarily over-represented in lower socioeconomic groups who may drive the risk of 

transmission.

Dr. Weiser (IHS) expressed appreciation for the comments regarding booster doses and the 

impact of severe disease among minority populations, especially those under the age of 65 

years. Despite the lack of data on waning of the vaccines in these populations, there is evidence 

of severe disease occurring in younger ages in these populations. Policy Question #2 would 

give IHS clinicians the flexibility to provide booster doses to patients who are medically fragile, 

with multiple medical conditions that put them at high risk for severe disease. Regarding 

feasibility, the AI/AN population had the highest uptake of COVID vaccination. Many of these 

vaccines were delivered in IHS Tribal & Urban Indian Health Centers. Those who were going to 

IHS clinics also have a place they can go where their medical history is known. The ability to 

understand those who are most at risk and might need a booster dose increases the feasibility 

in the IHS setting. He suspected that the population who are accessing the Federally Qualified 

Health Centers (FQHCs) also would receive similar care in a similar setting where their medical 

history is known and they can receive their booster doses in a place where they know their PCP 

and have the ability to discuss whether they want to receive a booster dose. He thought booster 

doses would be very welcomed in the IHS population and they have a proven track record for 

feasibility in distributing doses.
ACIP Meeting Summary September 22-23, 2021

86

Speaking as a practicing physician, Dr. Fryhofer (AMA) urged the ACIP members to vote for 

permissive use. As Dr. Fink said, the statutory requirement is that the booster may be effective 

to prevent serious disease or condition. There is so much evidence and data coming in every 

day, physicians like herself who care for patients with multiple medical problems need flexibility

in being able to recommend a booster for patients. Policy Question #1 includes over 65 years of 

age and LTCF residents. Many patients could be in LTCFs who are not 65 years of age or who 

live at home. Without flexibility, patients in need will be deprived of something that could save 

their lives. While she understood the need for making public health decisions, but this vaccine 

has been paid for by the government with tax dollars. There are patients whose VE is 

decreasing who have multiple medical problems who are very likely going to be some of the 

ones who die if they get sick. There is so much about this pandemic that is out of control. They 

cannot make people wear masks or control everything that happens. Making vaccine available 

to those who want to get a booster is a way of supporting the people who have chosen to be 

fully vaccinated and appreciating the fact that they want to maintain their protection against this 

deadly disease.

Dr. Talbot pointed out that in reality, almost every American is at risk due to obesity or medical 

problems, and/or or live with someone who is high risk, and/or teach children who are not able 

to get vaccinated yet. While the FDA provided specific caveats, in some way it may make more 

sense to make it permissive for the US population. That way, patients can have conversations 

with their providers or pharmacists to think through those risks. She recognized that this would 

not be the way to stop hospitalizations, but for those who have been vaccinated and done their 

part it may be okay to say, “If you’re over 18 years of age and you would like a third dose, fine.”

Dr. Daley made a couple of broad and overarching comments before getting to the next stage of 

this conversation. One question he was asked in the last week or two regarded whether the 

recommendations made today reflect who they value in society. He wanted to be very clear in 

stating that they most certainly do not. The goal is to prevent serious illness from COVID-19 for 

everyone in the country. This is not about who deserves a booster, but instead about who needs 

a booster. If someone is in a group for whom boosters doses are not universally recommended, 

it is critically important to understand that the vaccine’s effectiveness against serious outcomes 

is already very high for those who received the primary series. He reiterated that the decision 

they would make would be interim decisions that could, would, and should be readdressed as 

the circumstances and data warrant. He was very concerned about the inability to explicitly 

address heterologous or mix and match vaccination during this meeting, but hopefully that can 

be addressed very soon.

Dr. Cohn emphasized that these are referred to as “interim recommendations” and will change 

in this ever-evolving situation.

Dr. Drees (SHEA) expressed appreciation for the fact that 2 doses were still considered to be 

fully vaccinated for HCW in particular versus stating that the booster dose is needed as well. 

That gives employers some flexibility as to whether to also require a third dose or not. She 

agreed that staffing is stretched and the resources are not available to do the mass vaccination 

clinics that were done in December and January for healthcare staff. Similar to Dr. Daley’s 

comments, the data really support lowering of protection for Pfizer and that may change for the 

others as well. Starting with Pfizer makes sense and is more manageable from a resource 

standpoint.
ACIP Meeting Summary September 22-23, 2021

87

Dr. Cohn emphasized that supply for Pfizer vaccine is not an issue right now. There is plenty of 

Pfizer supply to continue to give the primary series and booster doses. Regarding capacity and 

whether offering booster vaccine will push out others who still need to get the primary series, the 

first priority will continue to be focused on getting people their primary series regardless if how 

the votes turned out during this meeting. One of the important communication messages is that 

not everybody will need a booster at 6 months. The language in the FDA EUA says that the 

booster can be given at any time after 6 months. While protection starts to wane, people are still 

highly protected. Many people may choose to get a booster dose at 7 months, 8 months, 9 

months, or 10 months.

Motion/Vote #1

Dr. Oliver (CDC/NCIRD) posted the following proposed recommendation for ACIP Vote #1 

Interim Recommendation:

A single Pfizer-BioNTech COVID-19 vaccine booster dose is recommended for persons 

aged ≥65 years, and long-term care facility (LTCF) residents, at least 6 months after 

the primary series under the FDA’s Emergency Use Authorization.

Motion/Vote #1 Interim Recommendation

Dr. Ault made a motion, which Dr. Poehling seconded, to adopt the language for Vote #1 as 

presented. No COIs were declared. The motion carried with 15 affirmative votes, 0 negative 

votes, and 0 abstentions. The disposition of the vote was as follows:

15 Favored: Ault, Bahta, Bell, Brooks, Chen, Cineas, Daley, Kotton, Loehr, Long, Lee, 

McNally, Poehling, Sanchez, Talbot

 0 Opposed: N/A

 0 Abstained: N/A

Motion/Vote #2

Dr. Oliver (CDC/NCIRD) posted the following proposed recommendation for ACIP Vote #2 

Interim Recommendation:

A single Pfizer-BioNTech COVID-19 vaccine booster dose is recommended for persons 

aged 50-64 years with underlying medical condition at least 6 months after the 

primary series under the FDA’s Emergency Use Authorization.

Motion/Vote #2 Interim Recommendation

Dr. Poehling made a motion, which Dr. Daley seconded, to adopt the language for Vote #2 as 

presented. No COIs were declared. The motion carried with 13 affirmative votes, 2 negative 

votes, and 0 abstentions. The disposition of the vote was as follows:

13 Favored: Ault, Bahta, Brooks, Chen, Cineas, Daley, Kotton, Loehr, Lee, McNally, 

Poehling, Sanchez, Talbot

 2 Opposed: Bell, Long

 0 Abstained: N/A
ACIP Meeting Summary September 22-23, 2021

88

Motion/Vote #3

Dr. Oliver (CDC/NCIRD) posted the following proposed recommendation for ACIP Vote #3

Interim Recommendation:

A single Pfizer-BioNTech COVID-19 vaccine booster dose is recommended for persons

based on individual benefit and risk who are aged 18-49 years with underlying 

medical conditions, at least 6 months after the primary series under the FDA’s 

Emergency Use Authorization.

Motion/Vote #3 Interim Recommendation

Dr. Brooks made a motion, which Dr. Ault seconded, to adopt the language for Vote #3 as 

presented. No COIs were declared. The motion carried with 9 affirmative votes, 6 negative 

votes, and 0 abstentions. The disposition of the vote was as follows:

 9 Favored: Ault, Brooks, Chen, Cineas, Daley, Kotton, Lee, Poehling, Talbot

 6 Opposed: Bahta, Bell, Loehr, Long, McNally, Sanchez

 0 Abstained: N/A

Motion/Vote #4

Dr. Oliver (CDC/NCIRD) posted the following proposed recommendation for ACIP Vote #4 

Interim Recommendation:

A single Pfizer-BioNTech COVID-19 vaccine booster dose is recommended based on 

individual benefit and risk for persons aged 18-64 years who are in an occupational 

or institutional setting where the burden of COVID-19 infection and risk of 

transmission are high, at least 6 months after the primary series under the FDA’s 

Emergency Use Authorization.

Discussion Points

Dr. Long thought this proposed recommendation was very difficult to interpret and too openended in the way it was stated. These are properly vaccinated people for whom it is known that 

the risks of breakthrough and severe disease are very low. Moreover, there is a lack of data for 

need in any of these groups.

Dr. Sanchez agreed with Dr. Long and thought they might as well just recommend that the 

booster dose be given to everybody 18 years of age and older. They should not give the 

impression that the vaccine in not working. The Pfizer-BioNTech COVID-19 vaccine is highly 

effective and is working, though certainly some higher risk individuals have some waning 

immunity with time.

Dr. Lee emphasized to clinicians and the public that the benefit/risk balance is individualized. 

ACIP has previously discussed the risk of myocarditis following vaccination and the many 

uncertainties around that. She wanted to make sure that if individuals choose to receive an 

additional dose that they do weigh the benefits and risks to themselves, particularly if they are 

younger and male receiving an mRNA vaccine. There are many individual patients and 

scenarios for whom she does believe access would be helpful for them and their families. While 
ACIP Meeting Summary September 22-23, 2021

89

she also was torn about this recommendation, she favored it in part because she felt like in this 

case access and outstanding patient, public, and provider education are needed. If this all could 

be done together, it would preserve access for individuals and their families.

Dr. Brooks spoke in favor of the motion. He acknowledged that everything everyone had said 

thus far was basically true, what was the conundrum. Given that these are difficult decisions, an 

individual benefit and risk determination must be made. If someone who is 18 and works in a 

shelter feels that he or she needs a booster, that would be the individual decision. However, he 

does not believe everyone who is 18 who works in a shelter is going to go get a booster. Some 

who is 64 years of age working in a shelter might decide to get a booster. He thought the 

language of the proposed recommendation spoke to everything people were saying and 

reflected that this is where the pandemic is right now.

Dr. Kotton highlighted that while this is a huge category of people, it may be one of the ways to 

better protect the estimated 3% of the US population who are immunocompromised and at 

higher risk and may not be well-protected even after a third dose of vaccine. Better protecting 

the people around them, often referred to as “cocooning” the patient, may help protect them.

While she did not like the language proposed and preferred to delay on this recommendation, 

but would vote yes if they did take a vote at this time.

Dr. Sanchez pointed out that this proposed recommendation may not take into account the 

cocooning effect for pediatric patients, given that those parents or caregivers may not be in an 

occupational or institutional setting. With the vaccines mandates that are being proposed and 

implemented, including in healthcare settings, he thought it would be important if this 

recommendation passed, it would be necessary to ensure that a fully vaccinated person has 

received a booster dose.

Dr. Cohn reminded everyone that vaccine safety is the top priority. As individuals get boosters, 

vaccine safety data will be presented again to ACIP in the very near future. If there are any 

concerning signals for increased risk of myocarditis in younger persons who receive a booster, 

those data will be presented immediately to ACIP for consideration. Just like the original vaccine 

rollout, vaccine safety will remain a top priority.

Dr. Lee asked whether the word “institution” needed to be included or if they could state 

“occupation or setting where the burden of COVID infection and risk of transmission are high?”

Dr. Cohn said that they could change the language to state, “Recommended based on 

individual benefits and risks for persons aged 18-64 who are in an occupation or setting where 

the burden of COVID-19, acute infection, and risk of transmission are high.” They could vote on 

that language if ACIP preferred, but they would have to ensure that the language was wellaligned with the FDA language.

It appeared to Dr. Long that ACIP would be expanding on the FDA approval. While they could 

do this, it is very unusual for ACIP to let light shine between the FDA and the CDC in terms of 

expansion. This does not at all include the requirement as she understood it for risk of severe 

COVID disease. It is very unusual for ACIP to let individuals decide on vaccine policy.

Dr. Lee pointed out that they should vote the intent and then seek additional guidance from 

CDC and FDA colleagues to ensure that the intent was as written.
ACIP Meeting Summary September 22-23, 2021

90

Dr. Cohn added that to stay within the spirit and intent of the FDA language, she would like to 

keep “occupational or institutional setting.” She emphasized that these recommendations will 

continue to evolve.

Ms. McNally found this to be challenging because she thought they were making some 

assumptions about health literacy that may be problematic, and that implementation of this 

recommendation would be very challenging.

Dr. Lee agreed and stressed that she was struggling with how much to assume and enable or 

not enable access versus how much needs to be done to move forward and put out all tools 

possible, which will never be enough, to ensure that everyone is fully educated on the benefits 

and risks.

Ms. Stinchfield (NAPNAP) added that in terms of implementation, the proof of one’s risk in a 

clinical, public health, or pharmacy setting would be next to impossible to ascertain. She has 

done a lot of mass vaccination clinics for HCW and communities. The burden would be high and 

cause undue stress on a stressed out healthcare system if people have to go to their clinicians 

to acquire documentation and then take that to a community vaccine setting.

Dr. Dooling reminded everyone that approximately 70% of COVID vaccines are now given in the 

setting of a pharmacy. As with the primary series, any booster would require self-attestation and

no additional onus for documentation.

Dr. Chen said that he had been very uncomfortable with his own thinking through Vote #3, and

he was even more uncomfortable with Vote #4. The focus of this proposed recommendation 

was not really about direct benefit to the person being vaccinated, but instead focused on 

indirect benefit to the people surrounding them. It is known that indirect benefit is largely to be 

gained by getting their primary series. It is not the answer to give them boosters, especially for 

this age group that does not have underlying medical conditions or predictors that would put 

them at the highest risk for severe effects of COVID infection. Again, the implementation 

aspects of this would be fraught with such complexity such that people with great health literacy 

will get boosters even though they are not really the ones who will get incremental benefit from 

this or indirect benefit for the people around them.

Dr. Drees (SHEA) noted that from a healthcare workforce perspective, she agreed with Dr. Long 

that most of these people are not at risk for severe disease, they certainly have been getting 

infected at increasing rates over the last month or so even though they are fully vaccinated. It is 

difficult to predict which ones will develop long COVID symptoms. They have been on the 

frontlines from the beginning and even though they have and use PPE to protect themselves, it

is very frustrating and demoralizing to them to get COVID anyway. Therefore, she thought it was 

reasonable to include them in this vote.

Dr. Long emphasized that the goal should be use the vaccines in hand to immunize everyone in 

order to protect people from severe morbidity and death and not have to worry about who has 

coronavirus, who cannot go to school, et cetera. Primary prevention and prevention of the worst 

cases must be dealt with, which are no doubt going to be the most contagious. She did not think 

this vaccine would protect against acquisition or transmission for more than a couple of 

months—even the booster.
ACIP Meeting Summary September 22-23, 2021

91

Dr. Cohn emphasized that this was not an either/or vote. The primary focus of public health is 

and will remain on the primary series and there is ample vaccine supply. She appreciated all of 

the very important concerns raised, but reiterated that this vote would be to allow an individual 

in one of these settings make a decision to have access to and be vaccinated with a booster 

dose.

Dr. Shah (ASTHO) commented that from a state health department perspective, this would be 

exceedingly challenging from an implementation perspective. The analysis required to 

effectuate this recommendation proceeds along two axes. The first is the pros and cons of the 

individual benefit determination and then secondarily or in concert with that is the nature of the 

occupational and institutional risk. Many patients themselves may not know exactly what the 

components of the individual risk information, let alone their occupational risks. Even if a patient 

were to know that information, the staff in a pharmacy or a largescale vaccination site on a 

given day may themselves not have the wherewithal to make that determination and effectuate 

it in the manner that ACIP may intend. He certainly agreed with the public health spirit 

underlying the proposed recommendation, but posited that this would result in the inevitable 

confusion and patchwork that occurred back in January and February.

Dr. Zahn (NACCHO) said that speaking from the local public health standpoint, this 

recommendation would be extraordinarily difficult to implement. It essentially would convey to 

individuals to assess their own situation and get vaccinated with a booster if they think it is 

appropriate. As Dr. Chen noted, people are vaccinated to protect themselves. In most of the 

high risk situations mentioned, people actually acquire infection at home or in the community. 

For instance, the primary risk for HCW acquiring COVID-19 is in the community. From a public 

health standpoint, it is important to convey that a vaccine is being recommended to protect the 

recipient rather than making them more consistently available as part of a workforce.

Dr. Talbot emphasized that HCW are getting COVID in the community and their children are 

going back to school and cannot yet be vaccinated. The longer that HCW are symptomatic or 

have even a mild COVID illness, they cannot go to work and hospitals cannot be sufficiently 

staffed. Many states are experiencing this issue and having the option to give HCW a third dose 

will help to maintain staffing. While there are caveats and groups who may not be the best fit for 

this recommendation, HCW are critical and cannot be forgotten.

Dr. Goldman (ACP) said he thought this was a solution looking for a problem that would not 

address the issue of the pandemic and that would create more confusion for providers at the 

implementation level. In addition, he thought it was going far afield of the data and what they are 

trying to accomplish from a public health perspective.

Dr. Lee made a personal comment that she did not support this as a full recommendation 

because of all of the concerns raise throughout the day. She has cared for children who have 

died from COVID, whose family members wished that they had extra protection for their children 

because they were not symptomatic and no one else was sick at home. Some family members 

wish to provide this extra level of protection and are willing to take that risk. Although she 

shared all of the same concerns about safety, health literacy, et cetera, access was very 

important to her and she worried that by inhibiting access to this, some individuals and families 

may suffer. If this were a full standard recommendation, she could not personally support it. 

Because it allowed for an individual risk/benefit decision, she viewed this as different.
ACIP Meeting Summary September 22-23, 2021

92

Dr. Daley said he was struggling with this as well. Another consideration was that it felt broad 

enough that it potentially could limit access to other groups such as those over 65 years of age 

and those 18-64 with high risk conditions. He appreciated the intent of the proposed 

recommendation and agreed that they needed to think very carefully about the HCW workforce 

and staffing issues.

Motion/Vote #4 Interim Recommendation

Dr. Ault made a motion, which Dr. Kotton seconded, to adopt the language for Vote #4 as 

presented. The motion did not carry with 6 affirmative votes, 9 negative votes, and 0 

abstentions. The disposition of the vote was as follows:

 6 Favored: Ault, Brooks, Cineas, Kotton, Lee, Talbot

 9 Opposed: Bahta, Bell, Chen, Daley, Loehr, Long, McNally, Poehling, Sanchez 

 0 Abstained: N/A

Discussion Points

Subsequent to the vote, Dr. Lee invited ACIP members to make a statement about the rationale 

for their vote and/or to share any additional general comments.

Dr. Talbot requested to make an amendment to the language for a revote on the fourth interim 

recommendation.

Dr. Cohn responded that given the fact that the meeting had already gone over by 1.5 hours, 

additional votes would not be entertained and the meeting would be officially closed following 

any comments from ACIP members regarding their votes. However, consideration would be 

given to bringing this issue back to the table with potentially different options. There are several 

ACIP meetings ahead during which this could be done.

Ms. Bahta said she felt like they were being pulled into an emotional decision. The science 

shows that this is a very effective vaccine. This decision was made for the vaccinated, not the 

unvaccinated. She did not believe they had the data in the younger age groups to make a 

decision for a booster dose. To her, it would suggest that the vaccine does not work. While they 

know this is not true, that is likely how that message will be conveyed to the broader public. That 

was why she voted “not” for the third and fourth interim recommendations.

Dr. Ault indicated that he voted “yes” on the third recommendation because it would allow 

clinicians maximum leeway. There were some public comments and written comments in the 

docket stated the same thing. He voted “yes” on the fourth vote because like Dr. Talbot pointed 

out, there are areas with tremendous amounts of community spread where all hospitals big and 

small operating on the thinnest of margins. For HCW to be sick or take time off of work places 

systems at risk.

Dr. Bell agreed with everything Dr. Bahta said in explaining why she voted “no” and also to 

emphasize that this represented the beginning of a lot of activity around booster doses and 

other vaccination efforts that are forthcoming. In this situation, at this moment, and given the 

lack of evidence about the marginal benefits of booster doses for people in certain groups who 

received a Pfizer primary series, it was too narrow and too soon. In terms of the potential risks 

for adverse outcomes of waiting until more is known, there was little marginal benefit to making 

this booster dose available at this time in her opinion given all of the unknowns.
ACIP Meeting Summary September 22-23, 2021

93

Dr. Poehling pointed out that during the 30 hours since this meeting started, approximately 2400 

Americans died of COVID-19 and most of them were unvaccinated. This COVID-19 vaccine is 

the most studied vaccine in the US. The development and extensive evaluation and distribution 

of this vaccine, especially with such extraordinary cold-chain requirements, is an incredible 

example of what can be accomplished when data are openly shared and everyone collaborates 

and works together to achieve a goal. What has been learned about COVID-19 provides 

tremendous hope for the future, and it is possible to get to the other side of this pandemic by 

truly working together. It will require everyone. This biggest impact on the pandemic, which has 

been mentioned many times, has come from increasing vaccine coverage with the primary 

series and using the recommended measures. ACIP has openly shared what is and is not 

known. They should highlight that there is a lot that is known and that the primary series is 

highly effective. There is waning for persons over 65 years of age and there is concern about 

persons in LTCF and those 50 years of age and older with high risk conditions. For those 

reasons, she voted “yes.” While they do want to provide additional protection for those at 

increased risk, the most important thing they can do is ensure that they do not take away efforts 

from the primary series.

Closing Remarks and Adjournment 

Dr. Lee (ACIP Chair) thanked the speakers, CDC colleagues, members, ex officio members, 

and liaisons for an incredible 2-day meeting. She expressed appreciation for everyone’s input 

and respect for diverse opinions, as well as her hope that the discussions would be helpful to 

their colleagues who need to be able to explain policies and recommendations to their 

constituents. She anticipated that there would be another meeting soon as the data continued to 

evolve. As information emerges, ACIP will continue to be updated.

Dr. Cohn (ACIP Executive Secretary, CDC) reminded everyone that there would be a nonCOVID meeting on September 20, 2021 that would include a full day of exciting updates and 

information about everything but COVID. However, the agenda could be adjusted accordingly if 

new data emerge.

With no further business raised or questions posed, the meeting was officially adjourned.
ACIP Meeting Summary September 22-23, 2021

94

Certification

Upon reviewing the foregoing version of the September 22-23, 2021 ACIP summary minutes, 

Dr. Grace Lee, ACIP Chair, certified that to the best of her knowledge, they are accurate. 
ACIP Meeting Summary September 22-23, 2021

95

ACIP Membership Roster

CHAIR

LEE, Grace M., MD, MPH

Associate Chief Medical Officer for Practice Innovation

Lucile Packard Children’s Hospital

Professor of Pediatrics, Stanford University School of Medicine

Stanford, CA

Term: 8/4/2021 – 6/30/2023

EXECUTIVE SECRETARY

COHN, Amanda, MD 

Senior Advisor for Vaccines 

National Center for Immunization and Respiratory Diseases 

Centers for Disease Control and Prevention 

Atlanta, GA 

MEMBERS

AULT, Kevin A, MD, FACOG, FIDSA 

Professor and Division Director 

Department of Obstetrics and Gynecology University of 

Kansas Medical Center 

Kansas City, KS 

Term: 10/26/2018 – 6/30/2022 

BAHTA, Lynn, RN, MPH, CPH 

Immunization Program Clinical Consultant 

Infectious Disease, Epidemiology, Prevention & Control Division 

Minnesota Department of Health 

Saint Paul, Minnesota 

Term: 7/1/2019 – 6/30/2023

BELL, Beth P, MD, MPH 

Clinical Professor 

Department of Global Health, School of Public Health 

University of Washington 

Seattle, WA 

Term: 7/1/2019 – 6/30/2023 

BROOKS, Oliver, MD, FAAP

Chief Medical Officer

Watts HealthCare Corporation

Los Angeles, CA

Past President, National Medical Association

Term: 7/26/2021 – 6/30/2025
ACIP Meeting Summary September 22-23, 2021

96

CHEN, Wilbur H, MD, MS, FACP, FIDSA 

Professor of Medicine 

Center for Vaccine Development and Global Health 

University of Maryland School of Medicine 

Baltimore, MD 

Term: 12/23/2020 – 6/30/2024 

CINEAS, Sybil, MD, FAAP, FACP

Associate Professor of Medicine, Pediatrics, and Medical Science (Clinical)

The Warren Alpert Medical School of Brown University

Associate Program Director

Brown Combined Residency in Internal Medicine and Pediatrics

Providence, RI

Term: 7/28/2021 – 6/30/2025

DALEY, Matthew F, MD 

Senior Investigator 

Institute for Health Research, Kaiser Permanente Colorado 

Associate Professor of Pediatrics 

University of Colorado School of Medicine 

Aurora, CO 

Term: 1/4/2021 – 6/30/2024 

KOTTON, Camille Nelson, MD, FIDSA, FAST

Clinical Director, Transplant and Immunocompromised Host Infectious Diseases

Infectious Diseases Division, Massachusetts General Hospital

Associate Professor of Medicine, Harvard Medical School

Boston, MA

Term: 12/23/2020 – 6/30/2022

LOEHR, James, MD, FAAFP

Owner, Cayuga Family Medicine

Ithaca, New York

Term: 7/26/2021 – 6/30/2025

LONG, Sarah S, MD 

Professor of Pediatrics 

Drexel University College of Medicine 

Section of Infectious Diseases 

St. Christopher’s Hospital for Children 

Philadelphia, Pennsylvania 

Term: 12/24/2020 – 6/30/2024 

MCNALLY, Veronica V, JD 

President and CEO Franny 

Strong Foundation 

West Bloomfield, Michigan 

Term: 10/31/2018 – 6/30/2022 
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97

POEHLING, Katherine A, MD, MPH 

Professor of Pediatrics and Epidemiology and Prevention 

Director, Pediatric Population Health 

Department of Pediatrics 

Wake Forest School of Medicine 

Winston-Salem, NC 

Term: 7/1/2019 – 6/30/2023 

SÁNCHEZ, Pablo J, MD 

Professor of Pediatrics 

The Ohio State University – Nationwide Children’s Hospital 

Divisions of Neonatal-Perinatal Medicine and Pediatric Infectious Diseases 

Director, Clinical & Translational Research (Neonatology) 

Center for Perinatal Research 

The Research Institute at Nationwide Children's Hospital

Columbus, Ohio 

Term: 7/1/2019 – 6/30/2023 

TALBOT, Helen Keipp, MD 

Associate Professor of Medicine 

Vanderbilt University 

Nashville, TN 

Term: 10/29/2018 – 6/30/2022 

EX OFFICIO MEMBERS 

Centers for Medicare and Medicaid Services (CMS)

HANCE, Mary Beth 

Senior Policy Advisor 

Division of Quality, Evaluations and Health Outcomes 

Children and Adults Health Programs Group 

Center for Medicaid, CHIP and Survey & Certification Centers 

for Medicare and Medicaid Services

Baltimore, MD 

Food and Drug Administration (FDA) 

FINK, Doran, MD, PhD 

Deputy Director, Clinical, Division of Vaccines and Related Products Applications 

Office of Vaccines Research and Review 

Center for Biologics Evaluation and Research 

Food and Drug Administration 

Silver Spring, MD 

Health Resources and Services Administration (HRSA) 

RUBIN, Mary, MD 

Chief Medical Officer 

Division of Injury Compensation Programs 

Rockville, MD 
ACIP Meeting Summary September 22-23, 2021

98

Indian Health Service (IHS) 

WEISER, Thomas, MD, MPH 

Medical Epidemiologist 

Portland Area Indian Health Service 

Portland, OR 

Office of Infectious Disease and HIV/AIDS Policy (OIDP)

KIM, David, MD, MA 

Director, Division of Vaccines, OIDP 

Office of the Assistant Secretary for Health 

Department of Health and Human Services 

Washington, DC 

National Institutes of Health (NIH) 

BEIGEL, John, MD 

Associate Director for Clinical Research 

Division of Microbiology and Infectious Diseases 

National Institute of Allergy and Infectious Diseases (NIAID)

Bethesda, MD 

LIAISON REPRESENTATIVES 

American Academy of Family Physicians (AAFP)

ROCKWELL, Pamela G, DO 

Associate Professor, Department of Family Medicine, University of 

Michigan Medical School 

Medical Director, Dominos Farms Family Medicine 

Ann Arbor, MI 

American Academy of Pediatrics (AAP) 

MALDONADO, Yvonne, MD 

Senior Associate Dean for Faculty Development and Diversity 

Professor of Pediatrics and Health Research and Policy 

Chief, Division of Pediatric Infectious Diseases 

Stanford University School of Medicine

Stanford, CA 

American Academy of Pediatrics (AAP) 

Red Book Editor

KIMBERLIN, David, MD 

Professor of Pediatrics 

Division of Pediatric Infectious Diseases 

The University of Alabama at Birmingham School of Medicine

Birmingham, AL 

American Academy of Physician Assistants (AAPA) 

LÉGER, Marie-Michèle, MPH, PA-C 

Senior Director, Clinical and Health Affairs 

American Academy of Physician Assistants

Alexandria, VA 
ACIP Meeting Summary September 22-23, 2021

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American College Health Association (ACHA) 

CHAI, Thevy S., MD 

Director of Medical Services 

Campus Health Services 

University of North Carolina at Chapel Hill

Chapel Hill, NC 

American College Health Association (ACHA) (alternate) 

MCMULLEN, Sharon, RN, MPH, FACHA 

Assistant Vice President of Student & Campus Life for Health and Wellbeing Cornell Health 

Ithaca, NY 

American College of Nurse Midwives (ACNM) 

HAYES, Carol E., CNM, MN, MPH 

Lead Clinician 

Clinical Quality Compliance and Management 

Planned Parenthood Southeast Atlanta, GA 

American College of Nurse Midwives (ACNM) (alternate) 

MEHARRY, Pamela M., PHD, CNM 

Midwifery Educator, Human Resources for Health 

In partnership with University of Rwanda and University of Illinois, Chicago 

American College of Obstetricians and Gynecologists (ACOG) 

ECKERT, Linda O, MD, FACOG 

Professor, Department of Obstetrics & Gynecology 

Adjunct Professor, Department of Global Health 

University of Washington 

Seattle, WA

American College of Physicians (ACP) 

GOLDMAN, Jason M, MD, FACP 

Affiliate Assistant Professor of Clinical Biomedical Science, Florida Atlantic University, Boca 

Raton, Florida 

Private Practice 

Coral Springs, FL 

American Geriatrics Society (AGS) 

SCHMADER, Kenneth, MD 

Professor of Medicine-Geriatrics Geriatrics 

Division Chief 

Duke University and Durham VA Medical Centers 

Durham, NC 

America’s Health Insurance Plans (AHIP) 

GLUCKMAN, Robert A, MD, MACP 

Chief Medical Officer, Providence Health Plans 

Beaverton, OR 
ACIP Meeting Summary September 22-23, 2021

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American Immunization Registry Association (AIRA) 

COYLE, Rebecca, MSEd 

Executive Director, AIRA Washington, DC 

American Medical Association (AMA)

FRYHOFER, Sandra Adamson, MD 

Adjunct Associate Professor of Medicine Emory 

University School of Medicine 

Atlanta, GA 

American Nurses Association (ANA) 

RITTLE, Charles (Chad), DNP, MPH, RN Assistant 

Professor, Nursing Faculty 

Chatham University, School of Health Sciences 

Pittsburgh, PA 

American Osteopathic Association (AOA) 

GROGG, Stanley E, DO 

Associate Dean/Professor of Pediatrics 

Oklahoma State University-Center for Health Sciences 

Tulsa, OK 

American Pharmacists Association (APhA) 

FOSTER, Stephan L, PharmD CAPT 

(Ret) USPHS 

Professor, College of Pharmacy 

University of Tennessee Health Sciences Center 

Memphis, TN 

Association of Immunization Managers (AIM) 

HOWELL, Molly, MPH 

Immunization Program Manager 

North Dakota Department of Health

Bismarck, ND 

Association for Prevention Teaching and Research (APTR) 

ZIMMERMAN, Richard, MD, MPH

Professor, University of Pittsburgh School of Medicine

Department of Family Medicine and Clinical Epidemiology

Pittsburgh, PA

Association of State and Territorial Health Officials (ASTHO) 

SHAH, Nirav D, MD, JD 

Director

Maine Center for Disease Control and Prevention

Augusta, ME 
ACIP Meeting Summary September 22-23, 2021

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Biotechnology Industry Organization (BIO) 

ARTHUR, Phyllis A, MBA 

Senior Director, Vaccines, Immunotherapeutics and Diagnostics Policy 

Washington, DC 

Council of State and Territorial Epidemiologists (CSTE) 

HAHN, Christine, MD 

State Epidemiologist 

Office of Epidemiology, Food Protection and Immunization Idaho 

Department of Health and Welfare 

Boise, ID 

Council of State and Territorial Epidemiologists (CSTE) (alternate) 

LETT, Susan, MD, MPH 

Medical Director, Immunization Program 

Division of Epidemiology and Immunization 

Massachusetts Department of Public Health 

Boston, MA 

Canadian National Advisory Committee on Immunization (NACI) 

QUACH, Caroline, MD, MSc 

Pediatric Infectious Disease Specialist and Medical Microbiologist 

Medical Lead, Infection Prevention and Control Unit 

Medical Co-director – Laboratory Medicine, Optilab 

Montreal-CHUM 

Montreal, Québec, Canada 

Infectious Diseases Society of America (IDSA) 

BAKER, Carol J., MD 

Professor of Pediatrics 

Molecular Virology and Microbiology 

Baylor College of Medicine 

Houston, TX 

International Society for Travel Medicine (ISTM) 

BARNETT, Elizabeth D, MD Professor of 

Pediatrics 

Boston University School of Medicine 

Boston, MA 

National Association of County and City Health Officials (NACCHO)

ZAHN, Matthew, MD 

Medical Director, Epidemiology 

Orange County Health Care Agency 

Santa Ana, CA 
ACIP Meeting Summary September 22-23, 2021

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National Association of County and City Health Officials (NACCHO) (alternate)

DUCHIN, Jeffrey, MD 

Health Officer and Chief, Communicable Disease

Epidemiology and Immunization Section 

Public Health - Seattle and King County 

Professor in Medicine 

Division of Allergy and Infectious Diseases 

University of Washington School of Medicine and School of Public Health

Seattle, WA 

National Association of Pediatric Nurse Practitioners (NAPNAP) 

STINCHFIELD, Patricia A, RN, MS, CPNP 

Director 

Infectious Disease/Immunology/Infection Control

Children's Hospitals and Clinics of Minnesota 

St. Paul, MN 

National Foundation for Infectious Diseases (NFID) 

SCHAFFNER, William, MD 

Chairman, Department of Preventive Medicine 

Vanderbilt University School of Medicine 

Nashville, TN 

National Foundation for Infectious Diseases (NFID) (alternate)

DALTON, Marla, PE, CAE 

Executive Director & CEO 

National Foundation for Infectious Diseases (NFID) 

Bethesda, MD 

National Medical Association (NMA) 

WHITLEY-WILLIAMS, Patricia, MD Professor and Chair 

University of Medicine and Dentistry of New Jersey Robert Wood 

Johnson Medical School 

New Brunswick, NJ 

Pediatric Infectious Diseases Society (PIDS) 

O’LEARY, Sean, MD, MPH 

Associate Professor of Pediatrics 

Pediatric Infectious Diseases 

General Academic Pediatrics 

Children’s Hospital Colorado 

University of Colorado School of Medicine 

Pediatric Infectious Diseases Society (PIDS) (alternate)

SAWYER, Mark H, MD 

Professor of Clinical Pediatrics 

University of California, San Diego School of Medicine 

San Diego, CA 
ACIP Meeting Summary September 22-23, 2021

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Pharmaceutical Research and Manufacturers of America (PhRMA) 

ROBERTSON, Corey, MD, MPH 

Senior Director, US Medical, Sanofi Pasteur 

Swiftwater, PA 

Society for Adolescent Health and Medicine (SAHM) 

MIDDLEMAN, Amy B, MD, MSEd, MPH 

Professor of Pediatrics 

Chief, Section of Adolescent Medicine 

University of Oklahoma Health Sciences Center

Oklahoma City, OK 

Society for Healthcare Epidemiology of America (SHEA)

DREES, Marci, MD, MS 

Chief Infection Prevention Officer & Hospital Epidemiologist 

ChristianaCare 

Wilmington, DE 

Associate Professor of Medicine 

Sidney Kimmel Medical College at Thomas Jefferson University Philadelphia, PA 
ACIP Meeting Summary September 22-23, 2021

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Acronyms Used in the Document

AAFP American Academy of Family Physicians 

AAP American Academy of Pediatrics

ACHA American College Health Association 

ACIP Advisory Committee on Immunization Practices

ACOG American College of Obstetricians and Gynecologists

ACP American College of Physicians 

ADCC Antibody-Dependent Cellular Cytotoxicity 

AE Adverse Event

AHIP America’s Health Insurance Plans

AI/AN American Indian/Alaskan Native 

AIM Association of Immunization Managers 

AIRA American Immunization Registry Association 

AMA American Medical Association

AOA American Osteopathic Association 

APhA American Pharmacists Association 

APRN Advanced Practice Registered Nurse

ASTHO Association of State and Territorial Health Officers 

BLA Biologics License Application 

Caltech California Institute of Technology

CBER Center for Biologics Evaluation and Research 

CCI Charlson Comorbidity Index 

CDC Centers for Disease Control and Prevention

CDER Center for Drug Evaluation and Research 

CICP Countermeasures Injury Compensation Program 

CID Clinical Infectious Disease

CISA Clinical Immunization Safety Assessment 

CKD Chronic Kidney Disease 

CLD Chronic Liver Disease 

CLI COVID-Like Illness 

CMI Cell-Mediated Immunity 

CMS Center for Medicare and Medicaid Services

COD Cause of Death

COI Conflict of Interest 

COVID-NET COVID-19-Associated Hospitalization Surveillance Network 

CSTE Council of State and Territorial Epidemiologists 

CVD Cardiovascular Disease 

DFO Designated Federal Official

DNA Deoxyribonucleic Acid 

DNR/DNI Do Not Resuscitate/Do Not Intubate 

DoD Department of Defense

DPA Dynamic Pregnancy Algorithm 

DSMB Data Safety Monitoring Board 

DVA Department of Veterans Affairs

ECMO Extracorporeal Membrane Oxygenation

ED Emergency Department

EDD Estimated Data of Delivery 

EHR Electronic Health Record 

EMR Electronic Medical Record 

ET Eastern Time

EtR Evidence to Recommendation 

EU European Union 
ACIP Meeting Summary September 22-23, 2021

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EUA Emergency Use Authorization 

FDA Food and Drug Administration

FQHC Federally Qualified Health Center 

GACVS Global Advisory Committee on Vaccine Safety 

GBS Guillain-Barré Syndrome 

GEE Generalized Estimating Equation 

GMC Geometric Mean Concentration

GMR Geometric Mean Ratio 

GMT Geometric Mean Titers 

GRADE Grading of Recommendation Assessment, Development and Evaluation 

HCO Health Care Organization 

HCP Healthcare Personnel / Providers

HCW Health Care Workers 

HEROESRECOVERHealthcare, Emergency Response, and Other Essential Workers Surveillance StudyResearch on the Epidemiology of SARS-CoV-2 in Essential Response Personnel 

HHS (Department of) Health and Human Services

HRSA Health Resources and Services Administration 

ICATT 

Partnership

Increasing Community Access to Testing Partnership

ICU Intensive Care Unit

IDSA Infectious Disease Society of America 

IHS Indian Health Service 

IIS Immunization Information Systems 

IM Intramuscular 

ISD Immunization Services Division 

ISO Immunization Safety Office

IVAC International Vaccine Access Center 

IVY Network Influenza and Other Viruses in the Acutely Ill Network

KPSC Kaiser Permanente Southern California 

LSR Living Systematic Review 

LTCF Long-Term Care Facilities 

MMWR Morbidity and Mortality Weekly Report

MI Myocardial Infarction 

NACCHO National Association of County and City Health Officials 

NACI National Advisory Committee on Immunization Canada

NAPNAP National Association of Pediatric Nurse Practitioners 

NCEZID National Center for Emerging and Zoonotic Infectious Diseases 

NCHHSTP National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention 

NCHS National Center of Health Statistics 

NCIRD National Center for Immunization and Respiratory Diseases 

NEJM New England Journal of Medicine

NFID National Foundation for Infectious Diseases 

NHSN National Healthcare Safety Network 

NIAID National Institute of Allergy and Infectious Diseases 

NICU Neonatal Intensive Care Unit 

NIH National Institutes of Health

NMA National Medical Association 

NNDSS National Notifiable Diseases Surveillance System 

NNV Number Needed to Vaccinate 

OID Office of Infectious Disease 

OIDP Office of Infectious Disease Policy and HIV/AIDS 

PBMC Peripheral Blood Mononuclear Cell

PCP Primary Care Provider/Practitioner

PCR Polymerase Chain Reaction 
ACIP Meeting Summary September 22-23, 2021

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PEA Pregnancy Episode Algorithm 

PHAC Public Health Agency Canada 

PICO Population, Intervention, Comparison, Outcomes 

PIDS Pediatric Infectious Disease Society 

PPE Personal Protective Equipment

PREP Act Public Readiness and Emergency Preparedness Act 

RA Rheumatoid Arthritis 

RCA Rapid Cycle Analysis

RCT Randomized Controlled Trial

RN Registered Nurse

RNA Ribonucleic Acid 

ROA Route of Administration 

RR Relative Risk

rRT-PCR Real-Time Reverse Transcription Polymerase Chain Reaction 

RT-PCR Reverse Transcriptase Polymerase Chain Reaction

SAB Spontaneous Abortion

SAE Serious Adverse Event 

SAGE Strategic Advisory Group of Experts on Immunization (WHO)

SAHM Society for Adolescent Health and Medicine 

SDOH Social Determinants of Health 

SHEA Society for Healthcare Epidemiology of America 

SME Subject Matter Expert

SNF Skilled Nursing Facility 

SUPERNOVA 

Network

SUrveillance Platform for Enteric and Respiratory iNfectious Organisms at the VA 

Network

SVI Social Vulnerability Index 

TTS Thrombotic Thrombocytopenia Syndrome 

UK United Kingdom

URI Upper Respiratory Infection 

US United States

USG United States Government

VA (US Department of) Veteran’s Affairs 

VAERS Vaccine Adverse Event Reporting System

VaST WG Vaccine Safety Technical Work Group 

VE Vaccine Efficacy

VE Vaccine Effectiveness

VRBPAC Vaccine and Related Blood Products Advisory Committee 

VSD Vaccine Safety Datalink

VYF Vaccinate Your Family

WG Work Group

WHO World Health Organization