National Center for Immunization & Respiratory Diseases

COVID-19 vaccine safety update

Advisory Committee on Immunization Practices (ACIP)

March 1, 2021

Tom Shimabukuro, MD, MPH, MBA

CDC COVID-19 Vaccine Task Force 

Vaccine Safety Team
2

Disclaimer

▪

▪

The findings and conclusions in this report are those of the authors 

and do not necessarily represent the official position of the Centers for 

Disease Control and Prevention (CDC) or the U.S. Food and Drug 

Administration (FDA).

Mention of a product or company name is for identification purposes 

only and does not constitute endorsement by CDC or FDA.
3

Topics 

▪

▪

▪

▪

▪

V-safe update

Vaccine Adverse Event Reporting System (VAERS) update

Vaccine Safety Datalink (VSD) update

Clinical Immunization Safety Assessment (CISA) Project update

COVID-19 vaccine safety in pregnancy
4
5

1. text message check-ins from CDC (daily 1st week; 

weekly thru 6 weeks; then 3, 6, and 12 mo.)

vaccine recipient completes web survey*

2. clinically 

important 

health 

impact 

reported

3. V-safe call center conducts active 

telephone follow-up on a clinically 

important event and takes a 

VAERS report if appropriate

✓ received medical care

Call center

4. pregnancy registry team conducts 

outreach to assess eligibility for 

registry and obtain consent for 

enrollment and follow-up

Call center

Vaccine recipients 

* Selected web surveys capture information on pregnancy status
6

Summary of v-safe data as of 

February 16, 2021

PfizerBioNTech Moderna Total 

People receiving 1 or more 

doses in the United States* 28,374,410 26,738,383 55,220,364

Registrants completing at least 

1 v-safe health check-in 1,776,960 2,121,022 3,897,982

Pregnancies reported to v-safe† 16,039 14,455 30,494

* COVID Data Tracker as of Feb 16, 2021 (107,571 doses with manufacturer not identified)

† Self-reported during a v-safe health check-in
* Gee J, Marquez P, Su J, et al. First Month of COVID-19 Vaccine Safety Monitoring — United States, December 14, 2020–January 13, 2021. MMWR Morb Mortal Wkly Rep. ePub: 19 7

February 2021. DOI: http://dx.doi.org/10.15585/mmwr.mm7008e3
* Gee J, Marquez P, Su J, et al. First Month of COVID-19 Vaccine Safety Monitoring — United States, December 14, 2020–January 13, 2021. MMWR Morb Mortal Wkly Rep. ePub: 19 8

February 2021. DOI: http://dx.doi.org/10.15585/mmwr.mm7008e3
9

+

co-managed by

CDC and FDA

Vaccine Adverse Event 

Reporting System

http://vaers.hhs.gov

VAERS is the nation’s early warning system for vaccine safety
10

Vaccine Adverse Event Reporting System (VAERS)

Strengths

▪ National data 

▪ Rapidly detects safety signals 

▪ Can detect rare adverse events

▪ Data available to public

Limitations

▪ Reporting bias 

▪ Inconsistent data quality and 

completeness of information

▪ Lack of unvaccinated comparison group

▪ Not designed to assess causality

‒

‒

VAERS accepts all reports from everyone regardless of the plausibility of the 

vaccine causing the event or the clinical seriousness of the event

As a hypothesis-generating system, VAERS identifies potential vaccine safety 

concerns that can be studied in more robust data systems
11

U.S. reports to VAERS after COVID-19 vaccines 

through February 16, 2021*

Vaccine N

Non-serious 

AEs (%)

Serious 

AEs†§(%)

Moderna 56,567 54,708 (97) 1,859 (3)

Pfizer-BioNTech 48,196 43,974 (91) 4,222 (9)

Total 104,763 98,682 (94) 6,081 (6)

* Total pre-processed reports (reports received and classified as serious or non-serious)

† Based on the Code of Federal Regulations if one of the following is reported: death, life-threatening illness, hospitalization or prolongation of hospitalization, permanent disability, congenital anomaly 

or birth defect

§ Most commonly reported serious adverse events include: death (456 reports of death following Moderna vaccine and 510 following Pfizer-BioNTech vaccine), dyspnoea, pyrexia, SARS-CoV-2 test 

negative, nausea, headache, dizziness, fatigue, asthenia, pain
12

Most commonly reported adverse events to VAERS 

after COVID-19 vaccines through February 16, 2021*

Pfizer-BioNTech

* For reports received and processed (coded, redacted, and quality assurance performed)

†Adverse events are not mutually exclusive

Adverse event† N (%)

Headache 2,322 (20.0)

Fatigue 1,801 (15.5)

Dizziness 1,659 (14.3)

Pyrexia 1,551 (13.4)

Chills 1,508 (13.0)

Nausea 1,482 (12.8)

Pain 1,464 (12.6)

SARS-CoV-2 Test Positive 1,002 (8.6)

Injection Site Pain 997 (8.6)

Pain in Extremity 923 (8.0)

Adverse event† N (%)

Headache 1,353 (23.4)

Pyrexia 1,093 (18.9)

Chills 1,056 (18.3) 

Pain 945 (16.3) 

Fatigue 888 (15.4) 

Nausea 884 (15.3) 

Dizziness 792 (13.7) 

Injection Site Pain 671 (11.6) 

Pain in Extremity 576 (10.0) 

Dyspnoea 487 (8.4) 

Moderna

▪ No empirical Bayesian data mining alerts (EB05 ≥2) detected for any adverse 

event-COVID-19 vaccine pairs (most recent weekly results)
13

Anaphylaxis following mRNA COVID-19 vaccines

Shimabukuro TT, Cole M, Su JR. Reports of Anaphylaxis After Receipt of mRNA 

COVID-19 Vaccines in the US-December 14, 2020-January 18, 2021. JAMA. 2021 

Feb 12. doi: 10.1001/jama.2021.1967. Epub ahead of print. 

Pfizer-BioNTech Moderna
14

VSD

Vaccine

Safety

Datalink

▪

▪

9 participating integrated healthcare organizations

data on over 12 million persons per year
15

birth and death 

certificate 

information & 

family linkage

immunization 

enrollment and records

demographics

Types of information in VSD

linked by 

study IDs

Images created by Wilson Joseph, Megan Mitchell, Ananth, and Iga from the noun project

outpatient and 

clinic visits

emergency room 

visits

procedure codes hospital discharge 

diagnosis codes

charts and 

electronic 

health records
16

VSD Rapid Cycle Analysis (RCA) for COVID-19 vaccines

▪ Data are refreshed weekly

▪ Outcomes monitored are pre-specified (i.e., identified in advance)

▪ Includes methods to adjust for sequential testing

▪ A surveillance activity, not the same as an epidemiologic study

▪ Designed to detect statistically significant associations and statistical signals 

(values above specified statistical thresholds)

▪ When a statistically significant association or signal occurs, assessment 

involves a series of checks and evaluations

▪ Chart-confirmation of diagnoses to confirm or exclude cases as true incident 

cases is a key part of statistical signal assessment 
17

VSD RCA for COVID-19 vaccines

▪

–

–

–

–

Analyses

Unvaccinated concurrent comparators (currently being conducted)

Vaccinated concurrent comparators (currently being conducted)

Self-controlled risk interval (planned)

Historical comparators (planned)
18

VSD COVID-19 vaccine doses administered by 

manufacturer through February 13, 2021*

* Source: VSD participating integrated healthcare organizations; total includes a small number of unknow vaccine type

-BioNTech

COVID-19 

vaccine doses 

administered
19

VSD COVID-19 vaccine doses administered by manufacturer, 

age group, and dose number through February 13, 2021*

-BioNTech

COVID-19 

vaccine doses 

administered

* Source: VSD participating integrated healthcare organizations; total includes a small number of unknow vaccine type
20

VSD Rapid Cycle Analysis prespecified 

outcomes for COVID-19 vaccines

Concurrent 

comparator 

analysis

Risk 

interval

Events in

vaccinated

Adjusted 

expected events 

in risk interval

Acute disseminated encephalomyelitis Unvaccinated 1-21 days 0 0

Acute myocardial infarction Unvaccinated 1-21 days 23 26.0

Acute respiratory distress syndrome Unvaccinated N/A 0 N/A

Anaphylaxis Unvaccinated 0-1 days 20 N/A

Appendicitis Unvaccinated 1-21 days 31 23.6

Bell’s palsy Unvaccinated 1-21 days 21 20.3

Convulsions/seizures Unvaccinated 1-21 days 10 9.6

Disseminated intravascular coagulation Unvaccinated 1-21 days 1 1.1

Encephalitis/myelitis/encephalomyelitis Unvaccinated 1-21 days 1 .1

Guillain-Barré syndrome Unvaccinated 1-21 days 1 .6

Thrombotic thrombocytopenic purpura Unvaccinated 1-21 days 0 0

Immune thrombocytopenia Unvaccinated 1-21 days 1 1

Kawasaki disease Unvaccinated 1-21 days 0 0

MIS-C and MIS-A Unvaccinated N/A 0 N/A

Myocarditis/pericarditis Unvaccinated 1-21 days 2 2.1

Narcolepsy and cataplexy Unvaccinated N/A 2 N/A

Stroke, hemorrhagic Unvaccinated 1-21 days 8 10

Stroke, ischemic Unvaccinated 1-21 days 41 38.8

Transverse myelitis Unvaccinated 1-21 days 0 0

Venous thromboembolism Unvaccinated 1-21 days 26 26.3

Pulmonary embolism (subset of VTE) Unvaccinated 1-21 days 20 21.0

Preliminary results of the VSD unvaccinated concurrent comparator analysis for COVID-19 

vaccine safety after either dose of any mRNA vaccine as of February 13, 2021

▪ No statistically 

significant 

increased risks 

detected for any 

prespecified 

outcomes
21

VSD Rapid Cycle Analysis prespecified 

outcomes for COVID-19 vaccines*

Concurrent 

comparator 

analysis

Risk 

interval

Events in

risk Interval

Adjusted 

expected events 

in risk interval

Statistical 

signal

(Y/N)

Acute myocardial infarction Vaccinated 1-21 days 21 30.8 N

Appendicitis Vaccinated 1-21 days 25 53.5 N

Bell’s palsy Vaccinated 1-21 days 17 23.1 N

Convulsions/seizures Vaccinated 1-21 days 10 9.4 N

Disseminated intravascular coagulation Vaccinated 1-21 days 1 0 N

Immune thrombocytopenia Vaccinated 1-21 days 1 0 N

Myocarditis/pericarditis Vaccinated 1-21 days 2 0 N

Stroke, hemorrhagic Vaccinated 1-21 days 7 0 N

Stroke, ischemic Vaccinated 1-21 days 37 43.5 N

Venous thromboembolism Vaccinated 1-21 days 23 12.4 N

Pulmonary embolism (subset of VTE) Vaccinated 1-21 days 19 0 N

Preliminary results of the VSD sequential vaccinated concurrent comparator

analysis for COVID-19 vaccine safety after either dose of any mRNA vaccine 

as of February 13, 2021

▪ No statistical signals detected

* Only includes outcomes with events in the risk window
22

VSD RCA next steps – next analyses

▪

▪

▪

▪

Dose-specific analyses

Product-specific analyses

Analyses for two risk intervals 1-21 and 1-42 days

Historical comparator analysis
23

7 participating medical 

research centers with 

vaccine safety experts

†More information about clinical consults available at: 

http://www.cdc.gov/vaccinesafety/Activities/CISA.html

CISA 

Clinical

Immunization

Safety

Assessment 

(CISA) Project 

▪▪

clinical consult services

†

clinical research
24

CISA Project COVIDvax

▪ Extension of CDC’s CISA* Project’s clinical consultation service for U.S. 

healthcare providers and health departments for complex COVID-19 vaccine 

safety questions/issues that are†

–

–

–

–

(1) about an individual patient(s) residing in the United States

(2) not readily addressed by CDC or ACIP guidelines 

▪ Vaccine safety subject matter expertise in multiple specialties (e.g., infectious 

diseases, allergy/immunology, neurology, OB/GYN, pediatrics, geriatrics) 

▪ Requests for a CISA consult about COVID-19 vaccine safety:

Contact CDC-INFO: 800-CDC-INFO (800-232-4636) or webform 

Indicate the request is for a “CDC CISA”* consult (no patient identifiers)

* https://www.cdc.gov/vaccinesafety/ensuringsafety/monitoring/cisa/index.html

† Advice from CDC and CISA is meant to assist in decision-making, rather than provide direct patient management 
25

CISA Project contributions

▪ Responded to 331 clinical inquiries or consultation requests about COVID-19 vaccine 

safety (December 14, 2020 through February 10, 2021)

–

–

–

–

–

Received from 43 states 

>90% from healthcare provider or health departments 

Most common topics include anaphylaxis/allergic reactions and nervous system disorders*

▪ Assisted state health departments with evaluation of complex medical issues 

pertaining to COVID-19 vaccines safety 

▪ Established CISA Project workgroup with allergy/immunology specialists

Provided expert input on anaphylaxis and other allergic reactions to inform clinical 

considerations for use of COVID-19 vaccines

Ongoing work to investigate possible mechanism for anaphylaxis after COVID-19 vaccine, 

in collaboration with FDA, NIH and other partners 

* Includes inquiries about adverse events and for clinical guidance without adverse event 
COVID-19 vaccine safety in pregnancy
27

Summary of v-safe data as of 

February 16, 2021

PfizerBioNTech Moderna Total 

People receiving 1 or more 

doses in the United States* 28,374,410 26,738,383 55,220,364

Registrants completing at least 

1 v-safe health check-in 1,776,960 2,121,022 3,897,982

Pregnancies reported to v-safe† 16,039 14,455 30,494

* COVID Data Tracker as of Feb 16, 2021 (107,571 doses with manufacturer not identified)

† Self-reported during a v-safe health check-in
V-safe: Day 1 post-vaccination local reactions in pregnant and nonpregnant women aged 16-54 years*

0

20

40

60

80

100

Pain Swelling Redness Itching

Percentage

Local Reactions

Pfizer-BioNTech Dose 1

0

20

40

60

80

100

Pain Swelling Redness Itching

Percentage

Local Reactions

Pfizer-BioNTech Dose 2

0

20

40

60

80

100

Pain Swelling Redness Itching

Percentage

Local Reactions

Moderna Dose 1

▀ 

▀ 

Pregnant (self-report)

Not pregnant

* Source: CDC unpublished v-safe data through January 13, 2021
0

20

40

60

80

100

Percentage

Systemic Reactions

Pfizer-BioNTech Dose 1

0

20

40

60

80

100

Percentage

Systemic Reactions

Pfizer-BioNTech Dose 2

0

20

40

60

80

100

Percentage

Systemic Reactions

Moderna Dose 1

V-safe: Day 1 post-vaccination local reactions in pregnant and nonpregnant women aged 16-54 years*

▀

▀ Not pregnant

 Pregnant (self-report)

* Source: CDC unpublished v-safe data through January 13, 2021
30

V-safe pregnancy registry

▪

▪

▪

V-safe participants who report pregnancy following COVID-19 

vaccination are actively contacted to enroll in pregnancy registry*

Participants are contacted once per trimester, after delivery, and when 

the infant is 3 months old†

Outcomes of interest include miscarriage and still birth, pregnancy 

complications, maternal intensive care unit admission, adverse birth 

outcomes, neonatal death, infant hospitalizations, and birth defects

* Must be registered in v-safe and have been pregnant at the time of COVID-19 vaccine receipt or within 30 days of vaccination; enrollment may discontinue 

when sufficient enrollment numbers are achieved

† Phone surveys are conducted along with maternal and infant medical record review
31

V-safe pregnancy registry enrollment 

as of February 19, 2021

Registry participants to date (N = 1,949)

Enrolled 1,815

Not eligible* 103

Refused/declined† 31

* Eligibility assessment determines whether vaccination was during pregnancy or within 30 days of last menstrual period

† Refused indicates those for whom eligibility could not be fully assessed because participant chose not to engage with pregnancy registry team; declined indicates those who were eligible to participate 

but chose not to enroll

▪ In the enrolled population, there have been 275 completed pregnancies, 

including 232 live births

‒ Other outcomes include miscarriage, stillbirth, ectopic/tubal, other
32

V-safe pregnancy registry outcomes of interest in COVID-19 

vaccinated pregnant women as of February 18, 2021*

Outcomes

Background 

rates*

V-safe pregnancy 

registry overall

Pregnancy outcome

Miscarriage (<20 weeks) 26% 15%†

Stillbirth (≥ 20 weeks) 0.6% 1%

Pregnancy complications 

Gestational diabetes 7-14% 10%

Preeclampsia or gestational hypertension§ 10-15% 15%

Eclampsia 0.27% 0%

Intrauterine growth restriction 3-7% 1%

Neonatal

Preterm birth 10.1% 10%

Congenital anomalies‡ 3% 4%

Small for gestational age^ 3-7% 4%

Neonatal death 0.38% 0%

* Sources listed on slide 33; † 93% of these were pregnancy losses <13 weeks of age; § Pre-eclampsia or gestational hypertension diagnosed during pregnancy and/or during delivery; ‡

Congenital anomalies (overall) diagnosed after delivery only; ^ Birthweight below the 10th percentile for gestational age and sex using INTERGROWTH-21st Century growth standards
33

Sources for pregnancy outcomes and complications and 

neonatal outcomes background rates 

▪ Miscarriage: https://www.ncbi.nlm.nih.gov/books/NBK532992/

▪ Stillbirth: https://www.cdc.gov/nchs/data/nvsr/nvsr69/nvsr69-04-508.pdf

▪ Gestational diabetes: https://dmsjournal.biomedcentral.com/articles/10.1186/s13098-019-0406-1, 

https://www.cdc.gov/pcd/issues/2018/18_0094.htm#:~:text=An%20estimated%201%25%20to%2014,

without%20gestational%20diabetes%20(4)

▪ Preeclampsia or gestational hypertension: 

https://www.frontiersin.org/articles/10.3389/fcvm.2020.00059/full, 

https://pubmed.ncbi.nlm.nih.gov/32381164/

▪ Eclampsia: CDC Wonder

▪ Intrauterine growth restriction: https://pubmed.ncbi.nlm.nih.gov/19404231/

▪ Preterm birth: NCHS/Peristats

▪ Congenital anomalies: https://www.cdc.gov/ncbddd/birthdefects/data.html

▪ Small for gestational age (this has it up to 11%): https://www.ncbi.nlm.nih.gov/books/NBK563247/

▪ Neonatal death: NCHS/Peristats
34

Characteristic

Maternal age in years, median (range) 33 (16–51)

Gestational age in weeks at time of vaccination when 

reported, median (range) 13 (2–38)

Trimester of pregnancy at time of vaccination n (%)

First (0-13 weeks) 60/118 (51)

Second (14-27 weeks) 36/118 (31)

Third (28+ weeks) 22/118 (19)

Vaccine

Pfizer-BioNTech 97 (63)

Moderna 56 (36)

Unreported 1 (0.6)

Characteristics of COVID-19 vaccine pregnancy reports to 

VAERS through February 16, 2021* (N=154)

* Reports received and processed through February 16, 2021
35

Adverse events N (%)

Pregnancy/neonatal specific conditions 42 (27)

Spontaneous abortion/miscarriage† 29

Premature rupture of membranes 3

Fetal hydrops 2

Neonatal death in 22-week preterm birth 1

Premature delivery 1

Gestational diabetes 1

Vaginal bleeding 1

Stillbirth 1

Shortened cervix 1

Leakage amniotic fluid 1

Calcified placenta 1

Non-pregnancy specific adverse events (top 10)

Headache (31), fatigue (29), chills (21), pain in extremity (17), nausea (15), dizziness 

(14), pain (14), pyrexia (13), injection site pain (13), injection site erythema (10)

112 (73)

Adverse events in pregnant women following COVID-19 vaccine 

reported to VAERS through February 16, 2021*(N=154) 

* Reports received and processed 

through February 16, 2021

† Frequency of clinically recognized 

early pregnancy loss for women aged 

20–30 years, 9–17%; age 30, 20%; age 

40, 40%; age 45, 80%. ACOG Practice 

Bulletin No. 200: Early Pregnancy Loss. 

Obstet Gynecol. 2018132(5):e197-e207
36

Other CDC COVID-19 maternal vaccination safety activities

▪ Vaccine Safety Datalink (VSD)

–

–

–

–

▪

COVID-19 vaccination coverage in pregnant women

Risk of miscarriage and stillbirth following COVID-19 vaccination

Safety in pregnancy

• Acute adverse events in pregnancy, longer-term safety assessment of acute 

adverse events, pregnancy complications and birth outcomes, and infant followup for the first year of life

Clinical Immunization Safety Assessment (CISA) Project

Prospective observational cohort study

• Adverse pregnancy and birth outcomes, serious adverse events, local and 

systemic reactogenicity, infant health outcomes for first 3 months of life
37

Maternal vaccination safety summary

▪

–

▪

▪

▪

▪

Pregnant women were not specifically included in pre-authorization clinical trials 

of COVID-19 vaccines

Post-authorization safety monitoring and research are the primary ways to 

obtain safety data on COVID-19 vaccination during pregnancy

Substantial numbers of self-reported pregnant persons (>30,000) have registered 

in v-safe

The reactogenicity profile and adverse events observed among pregnant women 

in v-safe did not indicate any safety problem

Most (73%) reports to VAERS among pregnant women involved non-pregnancyspecific adverse events (e.g., local and systemic reactions)

Miscarriage was the most frequently reported pregnancy-specific adverse event 

to VAERS; numbers are within the known background rates based on presumed 

COVID-19 vaccine doses administered to pregnant women
38

Closing thoughts on COVID-19 vaccine safety (Feb 2021)

▪ 75 million COVID-19 vaccine doses have been administered in the United 

States through February 28

▪ Reactogenicity profiles of mRNA vaccines in v-safe monitoring are consistent 

with what was observed in clinical trials, and systemic and local reactions are 

most commonly reported to VAERS

▪ Anaphylaxis following both vaccines has been reported to VAERS, though rarely

▪ No other safety signals for serious adverse events have been detected in VAERS 

▪ No safety concerns have been identified among VSD Rapid Cycle Analysis 

prespecified outcomes as of February 13

▪ No unexpected pregnancy or infant outcomes have been observed related to 

COVID-19 vaccination during pregnancy 

▪ Safety monitoring in pregnant women is ongoing and planned in v-safe, VAERS, 

VSD, and CISA
39

Acknowledgments

Centers for Disease Control and Prevention

COVID-19 Vaccine Task Force

COVID-19 Vaccine Task Force, Vaccine Safety Team

Immunization Safety Office

Division of Healthcare Quality Promotion

National Center on Birth Defects and Developmental Disabilities

Division of Reproductive Health 

Vaccine Safety Datalink

Clinical Immunization Safety Assessment Project

V-safe Team

U.S. Food and Drug Administration

Office of Biostatistics and Epidemiology

We wish to acknowledge the contributions of investigators from the following organizations:
Questions