cdc.gov/coronavirus

Overview of data to inform 

recommendations for booster doses 

of COVID-19 vaccines

Sara Oliver MD, MSPH

ACIP Meeting

June 23, 2021
Policy questions: 

Recommendations for booster doses of COVID-19 vaccines

2

▪ Main policy question: Are booster doses of COVID-19 vaccines needed for 

those previously vaccinated with a primary series? 

▪ Other questions:

– Are booster doses needed for all persons or only in specific populations? 

– What is the optimal timing of booster doses after primary series? 

– Can these be given as a ‘mixed dose’ or do they need to be matched to a primary 

series?

Note: Decisions around strains for vaccine production likely to be made separately 
Policy questions: 

Recommendations for booster doses of COVID-19 vaccines

3

▪ Policy on booster doses coordinated with FDA for possible amendments to 

EUA, and ACIP for recommendations around use in specific populations

– Both will require data on safety, immunogenicity and public health need

▪ “Booster dose”: Vaccine doses after primary (1 or 2-dose) series that are needed to 

increase immunity after waning of initial immune response

Some individuals may not have mounted sufficient immune response after primary 

series and could need an additional dose to reach protective immunity
4

Risk of 

COVID-19 

complications

Risk of 

COVID-19 

exposure

LTCF residents

Persons ≥65 years

Persons 16–64 with 

high-risk medical 

conditions

Health care personnel

Frontline Essential 

Workers

Other Essential 

Workers

Initial doses of COVID-19 vaccines:

Data to inform recommendations 

LTCF= Long Term Care Facility
5

Risk of 

COVID-19 

complications

Risk of 

COVID-19 

exposure

Risk of 

waning 

immunity

Risk of 

COVID-19 

variants

Booster doses of COVID-19 vaccines:

Data to inform recommendations 
6

Risk of 

COVID-19 

complications

Risk of 

COVID-19 

exposure

Risk of 

waning 

immunity

Risk of 

COVID-19 

variants

COVID-19 epidemiology

Cases, hospitalizations, 

deaths by age, setting, 

and medical condition

Booster doses of COVID-19 vaccines:

Data to inform recommendations 
7

Risk of 

COVID-19 

complications

Risk of 

COVID-19 

exposure

Risk of 

waning 

immunity

Risk of 

COVID-19 

variants

Duration of protection 

(antibodies, VE)

after primary series

Ability to ‘boost’ with 

additional doses

Booster doses of COVID-19 vaccines:

Data to inform recommendations 

VE= Vaccine efficacy/effectiveness
8

Risk of 

COVID-19 

complications

Risk of 

COVID-19 

exposure

Risk of 

waning 

immunity

Risk of 

COVID-19 

variants

Vaccine effectiveness studies 

& assessment of vaccine 

breakthrough cases

Time since vaccination, age,

setting, medical condition

Booster doses of COVID-19 vaccines:

Data to inform recommendations 
9

Risk of 

COVID-19 

complications

Risk of 

COVID-19 

exposure

Risk of 

waning 

immunity

Risk of 

COVID-19 

variants

Correlates 

of Protection

Booster doses of COVID-19 vaccines:

Data to inform recommendations 
Booster doses of COVID-19 vaccines:

Data to inform recommendations 

10

Risk of 

COVID-19 

complications

Risk of 

COVID-19 

exposure

Risk of 

waning 

immunity

Risk of 

COVID-19 

variants

Variant proportions,

antibody response, and 

effectiveness for each variant 

and vaccine
Booster doses of COVID-19 vaccines:

What do we know now?
COVID-19 vaccines administered

As of June 21, 2021

Total Vaccine Doses Administered:

318,576,441

CDC. https://covid.cdc.gov/covid-data-tracker

≥12 years of age:

62.5%

≥18 years of age:

65.4%

% of Population With 

At Least 1 Dose:

≥65 years of age:

87.3%
13

Booster doses of COVID-19 vaccines:

Immunogenicity and antibody response

▪ Correlates of protection: 

– Immune response that allows prediction of the degree of protection against 

infection or disease

– Work ongoing, no correlate established yet

▪ Duration of protection:

– Monitor kinetics of antibody response, efficacy from early phase clinical trials

▪ Antibody response to variant-specific boosters 
Robust correlation between vaccine efficacy against symptomatic 

disease and mean neutralizing antibody titer: Two studies

Khoury et al. Nature Medicine (2021) Earle et al. medRxiv preprint (Mar 20 2021)
Khoury et al. Nature Medicine (2021)

▪ Suggests 54 IU/ml as correlate of protection 

(20% of mean convalescent titer)

▪ Threshold of protection against severe disease

is lower (3% of mean convalescent titer), 

less affected by vaccine differences 

▪ For variants, 5-fold lower neutralizing titer 

predicted to reduce efficacy from 95% to 77% 

in high efficacy vaccine, or from 70% to 32% for 

lower efficacy vaccine

Robust correlation between vaccine efficacy against symptomatic 

disease and mean neutralizing antibody titer: Two studies
16

Predicted duration of immunity varies with initial vaccine efficacy

▪ Vaccine starting with initial efficacy of 95% 

expected to maintain high efficacy (77%) 

after 250 days

▪ Vaccine starting with initial efficacy of 70% 

may result in drop to lower efficacy (33%) 

after 250 days

▪ Model assumes neutralization is major 

mechanism of protection

▪ Initial efficacy may be useful in predicting time until boosting may be needed 

Khoury et al. Nature Medicine (2021)
17

Protection from severe infection predicted to persist longer than 

protection against mild infection

Khoury et al. Nat Med (2021). https://doi.org/10.1038/s41591-021-01377-8

▪ After initial exponential decay, antibody half-lives generally stabilize to ≥10 years (linear decline)

▪ Depending on when transition occurs, proportion of individuals predicted to be protected against 

severe disease long-term, even without boosters, but may be susceptible to mild infection
18

Duration of immunity

▪ To date, antibody persistence demonstrated for up to 8 months after COVID-19 

infection and up to 6 months after the 2nd mRNA vaccine dose

▪ Two studies, 6 months after receiving Moderna vaccine: Lower neutralizing 

titers & higher proportions (~50%) with undetectable titers against B.1.351 

and P.1, compared with ancestral strain

– Third modeling study makes similar conclusions

▪ Many studies have shown larger reductions in variant neutralization for 

convalescent sera than post-vaccine sera

Gaebler, C. et al. Evolution of antibody immunity to SARS-CoV-2. Nature 591, 639–644 (2021).

Dan, J. M. et al. Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection. Science 371, eabf4063 (2021)

Choe et al. Antibody Responses 8 Months after Asymptomatic or Mild SARS-CoV-2 Infection. Emerg Infect Dis. 2021;27(3):928-931. 

Doria-Rose et al. Antibody Persistence through 6 Months after the Second Dose of mRNA-1273 Vaccine for Covid-19. N Engl J Med 2021; 384:2259-226

https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-confirm-high-efficacy-and-no-serious

Khoury et al. Nat Med (2021). https://doi.org/10.1038/s41591-021-01377-8 ; Pegu et al. bioRxiv preprint (May 16 2021): https://doi.org/10.1101/2021.05.13.444010

Wu et al. medRxiv preprint (2021): https://doi.org/10.1101/2021.05.05.21256716 Luo, Hu, Letterio, medRxiv preprint (4 2021): medRxiv preprint doi: https://doi.org/10.1101/2021.05.04.21256537
19

Variant-specific booster

Preliminary analysis of safety and immunogenicity of a SARS-CoV-2 variant vaccine booster

▪ Two weeks after booster vaccination, titers against wild-type original strain, B.1.351 

and P.1 variants increased to levels similar to or higher than peak titers after the 

primary series vaccinations

https://www.medrxiv.org/content/10.1101/2021.05.05.21256716v1

50 μg booster dose of mRNA-1273 50 μg booster dose of mRNA-1273.351
20

Variant-specific booster

Preliminary analysis of safety and immunogenicity of a SARS-CoV-2 variant vaccine booster

▪ Both vaccines demonstrated broad antibody boosting 

https://www.medrxiv.org/content/10.1101/2021.05.05.21256716v1

50 μg booster dose of mRNA-1273 50 μg booster dose of mRNA-1273.351
21

Booster doses of COVID-19 vaccines:

Vaccine effectiveness

▪ Overall “real world” vaccine effectiveness 

▪ Efficacy/effectiveness against variants

▪ Effectiveness in specific populations
“Real world” vaccine effectiveness:

VE in fully vaccinated adult population

Fully vaccinated against COVID-19: ≥2 weeks after receipt of 2nd dose in a 2-dose series (Pfizer and Moderna) 

or ≥2 weeks after receipt of the single dose of the Janssen vaccine See reference list at end
B.1.429

Epsilon

B.1.526

Iota

B.1.526

+E484K

1

10

100

Fold reduction

Reduced antibody neutralization activity of vaccine sera 

relative to wildtype/dominant strain by study (n=48)

B.1.1.7 

Alpha

B.1.351

Beta

P.1

Gamma

P.2

Zeta 

B.1.1.7 

+E484K

mRNA 

Novavax 

AstraZeneca

Studies by 

vaccine

No effect =

B.1.617

B.1.617.1

Kappa

B.1.525

Eta

B.1617.2

Delta

Median: 7.5 3.0 2.8 1.9 2.0

Janssen

See reference list at end
“Real world” vaccine effectiveness:

Studies to inform VE against variants of concern

CDC Science Brief : https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html

Abu-Radad and Butt. NEJM (2021); Sandoff et al. NEJM (2021); Chung et al. medRxiv preprint (May 28 2021); Yassi et al. medRxiv preprint (May 25 2021)) 

Country Vaccine Dominant strain(s) Fully vaccinated VE

Israel, Europe & U.K Pfizer B.1.1.7 (Alpha) >85%

Canada mRNA B.1.1.7, P.1 (Alpha, Gamma) 79% (65%–88%)

Canada mRNA P.1/B.1.351 (Gamma/Beta) 88% (61%–96%)*

Qatar Pfizer B.1.1.7 (Alpha) 90% (86%–92%)*

B.1.351 (Beta) 75% (71%–79%)*

South Africa Janssen B.1.351 (Beta) 52% (30%–67%)

* Variant-specific VE

For B.1.351 (Beta), VE shown to be higher for prevention of severe disease
B.1.617.2-specific VE

▪ PCR-confirmed infection: Scotland, 2 doses Pfizer vaccine: 79% (vs. 92% for B.1.1.7)

▪ Symptomatic infection: England, 2 doses Pfizer vaccine: 88% (vs. 93% for B.1.1.7)

▪ Hospitalization: England, 2 doses Pfizer vaccine: 96% (similar to B.1.1.7)

B.1.617.2 antibody neutralization studies

▪ 4 studies, 2 doses Pfizer vaccine: 1.4, 2.5, 3, and 5.8-fold reduction (vs. wild-type)

Recent study in UK showing resurgence driven by replacement of B.1.1.7 

with B.1.617.2, which has higher transmission rate, and infections in unvaccinated 

children and young adults

Vaccines & new variant of concern: Delta B.1.617.2

Sheikh et al. Lancet (2021): https://doi.org/10.1016/S0140-6736(21)01358-1; Lopez Bernal et al. medRxiv preprint (May 26 2001); https://doi.org/10.1101/2021.05.22.21257658

Stowe et al. PHE preprint: https://khub.net/web/phe-national/public-library/-/document_library/v2WsRK3ZlEig/view/479607266 ; Planas et al. bioRxiv preprint (May 27 2021); 

https://doi.org/10.1101/2021.05.26.445838 ; Wall et al. Lancet (2021). https://doi.org/10.1016/ S0140-6736(21)01290-3: Liu et al. Cell (2021). https://doi.org/10.1016/j.cell.2021.06.020

Riley et al. medRxiv (June 21 2021): https://doi.org/10.1101/2021.06.17.21259103 ; Liu et al. Nature (2021); https://doi.org/10.1038/s41586-021-03693-y
26

Booster doses of COVID-19 vaccines:

Specific populations

▪ Need for booster doses of COVID-19 vaccines may only be demonstrated in 

some populations

▪ Populations to closely monitor: 

Residents of long-term 

care facilities Adults ≥65 years of age

Healthcare personnel Immunocompromised 

persons
Two-dose mRNA vaccine effectiveness against SARS-CoV-2 infection 

in older adults (60+ years) & residents in long-term care facilities 

Fully vaccinated against COVID-19: ≥2 weeks after receipt of 2 See reference list at end nd dose in a 2-dose series (Pfizer and Moderna) 
28

“Real world” vaccine effectiveness

Healthcare personnel 

Country Vaccine Fully vaccinated VE

United States Pfizer 97%

Moderna 99%

United States Pfizer or Moderna 90%

United States Pfizer 96%

United Kingdom Pfizer or AstraZeneca 90%

United Kingdom Pfizer 86%

United Kingdom (Scotland) Pfizer or AstraZeneca 92%

Italy Pfizer 95%

Denmark Pfizer 90%

VE against SARS-CoV-2 infection 

Country Vaccine Fully vaccinated VE

United States Pfizer or Moderna 94%

United States Pfizer 87%

Israel Pfizer 97%

Israel Pfizer 90%

VE against symptomatic COVID-19

https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html
▪ Represent ≥2.7% of U.S. adults1

, including people living with 

rheumatologic conditions, organ transplants, HIV, leukemia, on cancer 

treatment, etc.

▪ More likely to get severely ill from COVID-192

▪ Might be at higher risk for:

– Prolonged SARS-CoV-2 infection3-7

– Viral evolution during infection and treatment3,6,8-10

– Susceptibility to infection with SARS-CoV-2 variants12

▪ Might more frequently transmit SARS-CoV-2 to household contacts11

People with clinically or therapeutically suppressed 

immunity

(12) Stengert et al. Cellular and humoral immunogenicity of a SARS-CoV-2 mRNA vaccine inpatients on hemodialysis. medRxiv preprint 2021.
Factors that may decrease vaccine response among 

immunocompromised populations 

* Including lower CD4 count for people living with HIV

** Immunosuppressive drugs include methotrexate, mycophenolate, rituximab, infliximab, calcineurin-inhibitors

*** BTK inhibitors, anti-CD20 and anti-CD38 therapies, chemotherapy

Older age Primary 

immunodeficiency

Lower lymphocyte 

count*

Decreased kidney 

function

Immunosuppressive 

drugs**

High-dose 

corticosteroids

Current or recent 

(<6 mos) cancer 

treatment***
▪ 71% effective against SARS-CoV-2 infection from 7-27 days after 2nd Pfizer dose 

among immunocompromised* people vs. 90% overall

– 75% protection against symptomatic COVID-19 among immunosuppressed vs. 94% overall

– Lower protection with increasing age group

▪ 80% effective against SARS-CoV-2 infection from 7 days after 2nd mRNA dose 

among people with inflammatory bowel disease on various immunosuppressive 

medications

– One mRNA dose: 25% effective

– No difference in effectiveness noted between Pfizer and Moderna

mRNA vaccine effectiveness studies of COVID-19 infection 

among immunocompromised populations

*Immunocompromised conditions (e.g. recipients of hematopoietic cell or solid organs transplant, patients under immunosuppressive therapy, 

asplenia, and chronic renal failure: advanced kidney disease, dialysis, or nephrotic syndrome)

Chodick et al. Clinical Infectious Diseases, ciab438, https://doi.org/10.1093/cid/ciab438

Khan et al. Gastroenterology (2021). https://www.gastrojournal.org/article/S0016-5085(21)03066-3/pdf
Percent antibody response after two mRNA vaccine doses 

by immunocompromised condition and study (n=40)

Cancer Hemodialysis Organ Transplant Immunosuppressive

Therapies

• Studies that compared response after 1st and 2nd dose demonstrated poor response to dose 1

• Antibody measurement and threshold levels vary by study protocol 

Darker blue color is 

hematologic cancers

Healthy 

Controls:

95%–100%

0

20

40

60

80

100

Percent with antibody 

response (%) 

See reference list at end
0 5 10 15 20 25 30

Herishanu et al.

Parry et al.

Barriere et al.

Shroff et al.

Diefenbach et al.

Pimpinelli et al.

Massarweh et al.

Pimpinelli et al.

Simon et al.

Speer et al.

Grupper et al.

Jahn et al.

Strengert et al.

Yanay et al.

Korth et al.

Marinaki et al.

Grupper et al.

Miele et al.

Rabinowich et al.

Kennedy et al.

Haberman et al.

Geisen et al.

Fold-Reduction in Antibody Titer Compared to Healthy Controls 

75

Fold-reduction in antibody titers after two mRNA vaccine doses 

among immunocompromised populations vs. healthy controls

Darker blue color is 

hematologic cancers

Cancer

Hemodialysis 

Organ Transplant 

Immunosuppressive 

Therapies

73

1,315

1,350

See reference list at end
▪ Solid organ transplant recipients (n=30) who had suboptimal response to 

standard vaccination and subsequently received 3rd dose of vaccine

– 57% received Pfizer series; 43% received Moderna series

– 24 (80%) had negative antibody titers; 6 (20%) ‘low-positive’ after primary series

– Received 3rd dose median of 67 days after 2nd dose: Janssen (n=15), Moderna (n=9), Pfizer (n=6)

– After 3rd dose: 14 (47%) responded, including all low-positives; 16 (53%) remained negative

▪ People on hemodialysis (n=77, no COVID-19 history) vaccinated with up to 3 Pfizer doses

– 64 (83%) seroconverted after 2nd dose

– Of those negative after 2nd dose:

• 5 (41%) of 12 people given 3rd dose seroconverted; 7 (59%) remained negative

▪ At least one clinical trial pending of 3rd dose of Moderna vaccine in transplant recipients

Evidence on providing 3rd COVID-19 vaccine dose to 

immunosuppressed people with suboptimal response

Werbel et al. Annals of Internal Medicine. https://www.acpjournals.org/doi/pdf/10.7326/L21-0282

Longlune et al.. Nephrology Dialysis Transplantation, gfab193, https://doi.org/10.1093/ndt/gfab193

https://clinicaltrials.gov/ct2/show/NCT04885907
35

Considerations for specific populations

LTCF residents, adults ≥65 years of age

▪ Initial VE encouraging 

▪ Vaccinated in early phase of COVID-19 vaccine roll-out

▪ Needed special considerations for other vaccines (boosters, higher-dose vaccines)

Healthcare personnel

▪ Vaccinated in early phase of COVID-19 vaccine roll-out 

▪ Continued exposure to SARS-CoV-2, even as rates of community transmission improve

Immunocompromised persons

▪ Emerging literature suggesting a reduced antibody response after primary series

▪ By definition, population with an impaired immune response

▪ Concern for ability to mount an immune response after additional vaccine doses: 

consider if other prevention measures needed (monoclonal antibodies, etc.)
▪ Recent studies from Europe have assessed heterologous primary series 

with Pfizer and Astra Zeneca with reassuring results

▪ Evidence is needed regarding the ability to use a different vaccine as a 

booster than what was used in the primary series

– Studies specific to U.S. authorized vaccines

Mix-and-match: 

Heterologous primary series and booster vaccine

Borobia et. Al Reactogenicity and Immunogenicity of BNT162b2 in Subjects Having Received a First Dose of ChAdOx1s: Initial Results of a Randomized, Adaptive, Phase 2 Trial 

(CombiVacS). Available at SSRN: https://ssrn.com/abstract=3854768

Shaw et. al Heterologous prime-boost COVID-19 vaccination: initial reactogenicity data, ISSN 0140-6736, https://doi.org/10.1016/S0140-6736(21)01115-6.

Hillus D, Schwarz T, Tober-Lau P, et al. Safety, reactogenicity, and immunogenicity of homologous and heterologous prime-boost immunization with ChAdOx1-nCoV19 and 

BNT162b2: a prospective cohort study. medRxiv; 2021. DOI: 10.1101/2021.05.19.21257334.

Schmidt et al. medRxiv preprint (June 15 2021): https://doi.org/10.1101/2021.06.13.21258859
Booster doses of COVID-19 vaccines:

Timing of additional data
38

Upcoming studies: 

NIH or manufacturer studies

Data from Phase I/II/III trials

▪ Monitor kinetics of antibody response, efficacy from early phase clinical trials

▪ BLA submission: Include efficacy for ~6 months 

Heterologous boost

▪ Primary series followed by different boost vaccine

▪ NIH-sponsored study: 150 individuals, 12-20 weeks following initial series (any series) 

Results expected late summer 2021

Booster studies

▪ Moderna: Preliminary results for mRNA-1273 (50μg) published May 2021; 

Additional data on mRNA-1273 and other variants as boosters expected July-Sept 2021

▪ Pfizer: Data on BNT162b2 (30μg) and variant booster studies expected July-Sept 2021

https://www.nih.gov/news-events/news-releases/nih-clinical-trial-evaluating-mixed-covid-19-vaccine-schedules-begins
39

Upcoming studies: 

CDC studies

Vaccine breakthrough cases

▪ Track breakthrough infections

▪ Monitor severity of disease and genomic sequence (specifically for variants of concern)

Vaccine effectiveness studies

▪ Continue to monitor VE studies over time:

Stratify by age, time since vaccination, setting and medical condition 

▪ Ability to track any waning VE could be impacted by declining incidence, changes in 

variant prevalence

▪ Over time, individuals who are vaccinated may become increasingly less comparable to 

the unvaccinated population
40

Vaccine effectiveness: Select upcoming studies

HEROES-RECOVER Cohort

▪ Following ~5,000 essential workers with weekly SARS-CoV-2 testing and quarterly serology

▪ To date, fully vaccinated populations followed for ~130 days (~4 months) post-vaccination

▪ Assess neutralizing antibodies 6-months post-vaccination 

VISION VE Network

▪ Multi-state network of 8 integrated care systems and research centers; assess COVID-19 

confirmed by molecular assays and vaccination documented by EHR and registries

▪ Network assesses waning effectiveness using test-negative VE design 

IVY VE Network

▪ Collaborative of hospital-based investigators, through 18 tertiary academic medical 

centers in 16 states

▪ Plans to assess duration of protection by adapting prior methods used for influenza

EHR=Electronic Health Registries
Manufacturer data

Safety and Immunogenicity of booster doses

Timeline for additional data

Mix-and-match studies

Heterologous prime-boost

Summer:

July-September

Early Fall:

September-October

COVID-19 epi

Incidence of cases, hospitalizations, deaths

COVID-19 variants

Variant proportions, VE by variant

VE studies

VE by age, setting, time since vaccination

Breakthrough cases

Comparison of variants and clinical outcomes 

Manufacturer data 

Phase I/II/III follow-up
Manufacturer data

Safety and Immunogenicity of booster doses

Timeline for additional data

Mix-and-match studies

Heterologous prime-boost

Summer:

July-September

Early Fall:

September-October

COVID-19 epi

Incidence of cases, hospitalizations, deaths

COVID-19 variants

Variant proportions, VE by variant

VE studies

VE by age, setting, time since vaccination

Breakthrough cases

Comparison of variants and clinical outcomes 

Manufacturer data 

Phase I/II/III follow-up

ACIP meetings

Continue to provide updates. Vote could occur whenever data support updating policy
43

Booster doses of COVID-19 vaccines:

Work Group interpretation

▪ Work Group felt that recommendation for booster doses would only occur after: 

1. Evidence of declining protection against illness, such as declines in vaccine 

effectiveness, not only waning antibody response

2. An escape variant (variant of concern substantially impacting vaccine 

protection)

▪ No data to support recommendations for booster doses currently, but will 

continue to monitor

▪ Global vaccine availability should be considered in discussions as well 
44

Questions for ACIP

1. What does ACIP feel would be needed to move forward with booster 

recommendations? 

2. Is the risk of disease enough to warrant a recommendation for boosters, 

before additional data may be available? 
▪ Nicole Reisman

▪ Heather Scobie

▪ Meredith McMorrow

▪ Lauri Hicks

▪ Stephen Hadler

▪ Gayle Langley

▪ Jack Gersten

▪ Julia Gargano

▪ Jessica MacNeil

▪ Danielle Moulia

▪ Mary Chamberland

▪ Eddie Shanley

▪ Hannah Rosenblum

▪ Vaccine Task Force

▪ Epi Task Force

▪ Respiratory Viruses Branch

Acknowledgements
References
▪ Andrejko, Kristin, et al. "Early evidence of COVID-19 vaccine effectiveness within the general population of California." medRxiv (2021).

▪ Chodick, Gabriel, et al. "The effectiveness of the TWO-DOSE BNT162b2 vaccine: analysis of real-world data." Clinical Infectious Diseases (2021).

▪ Chung, Hannah, et al. "Effectiveness of BNT162b2 and mRNA-1273 COVID-19 vaccines against symptomatic SARS-CoV-2 infection and severe 

COVID-19 outcomes in Ontario, Canada." (2021).

▪ Corchado-Garcia, Juan, et al. "Real-world effectiveness of Ad26. COV2. S adenoviral vector vaccine for COVID-19." (2021).

▪ Dagan, Noa, et al. "BNT162b2 mRNA Covid-19 vaccine in a nationwide mass vaccination setting." New England Journal of Medicine 384.15 (2021): 

1412-1423.

▪ Goldberg, Yair, et al. "Protection of previous SARS-CoV-2 infection is similar to that of BNT162b2 vaccine protection: A three-month nationwide 

experience from Israel." medRxiv (2021).

▪ Haas, Eric J., et al. "Impact and effectiveness of mRNA BNT162b2 vaccine against SARS-CoV-2 infections and COVID-19 cases, hospitalisations, and 

deaths following a nationwide vaccination campaign in Israel: an observational study using national surveillance data." The Lancet 397.10287 

(2021): 1819-1829.

▪ Heymann, Anthony David, et al. "BNT162b2 Vaccine Effectiveness in Preventing Asymptomatic Infection with SARS-CoV-2 Virus: A Nationwide

Historical Cohort Study." Available at SSRN 3796868 (2021).

▪ Martínez-Baz, Iván, et al. "Effectiveness of COVID-19 vaccines in preventing SARS-CoV-2 infection and hospitalisation, Navarre, Spain, January to 

April 2021." Eurosurveillance 26.21 (2021): 2100438.

▪ Pawlowski, Colin, et al. "FDA-authorized COVID-19 vaccines are effective per real-world evidence synthesized across a multi-state health 

system." MedRxiv (2021).

▪ Pritchard, Emma, et al. "Impact of vaccination on new SARS-CoV-2 infections in the United Kingdom." Nature Medicine (2021): 1-9.

▪ Tande, Aaron J., et al. "Impact of the COVID-19 vaccine on asymptomatic infection among patients undergoing pre-procedural COVID-19 

molecular screening." Clinical Infectious Diseases: an Official Publication of the Infectious Diseases Society of America (2021).

References for Slide 22 (VE in General Adult Population)
References for Slide 27 (VE in Older Adults)

▪ Aran, Dvir. "Estimating real-world COVID-19 vaccine effectiveness in Israel using aggregated counts." medRxiv (2021).

▪ Cabezas et al. , Effects of BNT162b2 mRNA Vaccination on COVID-19 Disease, Hospitalisation and Mortality in Nursing Homes and Healthcare 

Workers: A Prospective Cohort Study Including 28,594 Nursing Home Residents, 26,238 Nursing Home Staff, and 61,951 Healthcare Workers in 

Catalonia. Available at SSRN: https://ssrn.com/abstract=3815682 or http://dx.doi.org/10.2139/ssrn.3815682

▪ Cavanaugh AM, Fortier S, Lewis P, et al. COVID-19 Outbreak Associated with a SARS-CoV-2 R.1 Lineage Variant in a Skilled Nursing Facility After 

Vaccination Program — Kentucky, March 2021. MMWR Morb Mortal Wkly Rep 2021;70:639-643. 

DOI: http://dx.doi.org/10.15585/mmwr.mm7017e2external icon

▪ Dagan, Noa, et al. "BNT162b2 mRNA Covid-19 vaccine in a nationwide mass vaccination setting." New England Journal of Medicine 384.15 (2021): 

1412-1423.

▪ Emborg, Hanne-Dorthe, et al. "Vaccine effectiveness of the BNT162b2 mRNA COVID-19 vaccine against RT-PCR confirmed SARS-CoV-2 infections, 

hospitalisations and mortality in prioritised risk groups." medRxiv (2021).

▪ Lopez-Bernal JL, Andrews N, Gower C, et al. Early effectiveness of COVID-19 vaccination with BNT162b2 mRNA vaccine and ChAdOx1 adenovirus 

vector vaccine on symptomatic disease, hospitalisations and mortality in older adults in England. medRxiv; 2021. DOI: 

10.1101/2021.03.01.21252652.

▪ Mason, Thomas FD, et al. "Effects of BNT162b2 mRNA vaccine on Covid-19 infection and hospitalisation among older people: matched case 

control study for England." medRxiv (2021).

▪ Moustsen-Helms, Ida Rask, et al. "Vaccine effectiveness after 1st and 2nd dose of the BNT162b2 mRNA Covid-19 Vaccine in long-term care facility 

residents and healthcare workers–a Danish cohort study." MedRxiv (2021).

▪ Public Health of England COVID-19 vaccine surveillance report Week 20 COVID-19 vaccine surveillance report - week 20 

(publishing.service.gov.uk)
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Populations) [1]

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