cdc.gov/coronavirus

Early safety monitoring for additional 

COVID-19 vaccine doses: 

Reports to VAERS and v-safe

Advisory Committee on Immunization Practices

October 21, 2021

Anne M. Hause, PhD MSPH

v-safe Team Co-Lead

COVID-19 Vaccine Task Force
CDC vaccine safety monitoring

v-safe VAERS VSD CISA Project

Full list of U.S. COVID-19 vaccine safety monitoring systems

https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety.html

• COVID-19 vaccines are being administered under the most intensive vaccine 

safety monitoring effort in U.S. history

• Strong, complementary systems are in place―both new and established 

2
CDC vaccine safety monitoring

v-safe VAERS VSD CISA Project

Full list of U.S. COVID-19 vaccine safety monitoring systems

https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety.html

• COVID-19 vaccines are being administered under the most intensive vaccine 

safety monitoring effort in U.S. history

• Strong, complementary systems are in place―both new and established 

3
+ 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

4
VAERS accepts reports from everyone

Key strengths

 Rapidly detects potential 

safety problems 

 Can detect rare adverse 

events

Key limitations

 Passive surveillance system

 Inconsistent quality and 

completeness of information

 Reporting biases

 Generally, cannot determine 

cause and effect

Regardless of the plausibility of the vaccine causing the event or the 

clinical seriousness of the event

5
Reports to VAERS following dose 3 mRNA or dose 2 Janssen 

COVID-19 vaccination, by age group and sex

Age group, years n (%)

12–17 34 (1)

18–49 1,225 (25)

50–64 1,304 (26)

≥65 2,427 (49)

Total 4,990

 Median age 64 years (interquartile range: 49-73)

 Majority (63%) among women

Sex n (%)

Male 1,823 (37)

Female 3,153 (63)

Unknown 14 (<1)

Total 4,990 

Includes data collected during August 12–October 10, 2021

6
Reports to VAERS following dose 3 

mRNA or dose 2 Janssen COVID-19 

vaccination, by race and ethnicity

Race or 

ethnicity

mRNA, 

dose 3 (%)

Janssen, 

dose 2 (%)

Hispanic or Latino 207 (4) 4 (10)

Non-Hispanic

AI/AN 21 (<1) 0 (0)

Asian 101 (2) 1 (3)

Black or AA 115 (2) 4 (10)

NHPI 3 (<1) 1 (3)

White 2,011 (41) 12 (31)

Multiracial 28 (1) 1 (3)

Other 24 (<1) 0 (0)

Unknown/

not reported 2,441(49) 16 (41)

Total 4,951 39

 Most reports either

• Unknown/not reported race or ethnicity (49%)

• White, non-Hispanic race and ethnicity (41%)

Includes data collected during August 12–October 10, 2021 for persons aged 12 years and older. Hispanic also includes persons identified of Hispanic ethnicity of unknown race. 

Abbreviations: AI/AN = American Indian/Alaska Native; AA = African American; NHPI = Native Hawaiian or other Pacific Islander. 

7
Reports to VAERS following dose 3 mRNA or dose 2 Janssen 

COVID-19 vaccination

Manufacturer Non-serious

reports

Serious

reports*

Total

reports

Pfizer-BioNTech 3,351 (95%) 160 (5%) 3,511

Moderna 1,325 (92%) 115 (8%) 1,440

Janssen 39 (100%) 0 (0%) 39

Total 4,715 (94%) 275 (6%) 4,990

 Regardless of manufacturer, ≥92% of reports non-serious

Includes data collected during August 12–October 10, 2021 for persons aged 12 years and older. 

* Per federal law, includes reports of hospitalization, prolongation of existing hospitalization, life threatening condition, permanent disability, congenital deformity or birth defect, or death. 8
Most frequently reported adverse events to VAERS following dose 3 

mRNA or dose 2 Janssen COVID-19 vaccination, by seriousness

Includes data collected during August 12–October 10, 2021 for persons aged 12 years and older. * Per federal law, includes reports of hospitalization, prolongation of existing hospitalization, life 

threatening condition, permanent disability, congenital deformity or birth defect, or death. ** Not mutually exclusive. 

Serious* (n = 275) Non-serious (n= 4,715)

Rank Adverse event** n (%)

1 Extra dose administered 40 (23)

2 Fever 38 (14)

3 Shortness of breath 37 (14)

4 Blood test 33 (12)

5 Fatigue 32 (12)

Rank Adverse event** n (%)

1 Interchange of vaccine 

products 1,110 (24)

2 Extra dose administered 969 (21)

3 Fever 764 (16)

4 Headache 697 (15)

5 Fatigue 665 (14)

9
Reports of death to VAERS following dose 3 mRNA or 

dose 2 Janssen COVID-19 vaccination

 Median age = 79 years (IQR: 69 – 88)

 Median time from third dose to 

death = 2 days (IQR: 0 – 9)

10

Preliminary impression of 

cause of death*

mRNA, 

dose 3

No cause specified 8

Found dead 4

Respiratory and/or cardiac arrest 3

Stroke 3

COVID-19 disease 3

Pneumonia; sepsis 2

Pulmonary embolism 2

Miscellaneous other† 5

Total 30

Includes data collected during August 12–October 10, 2021. Abbreviations: IQR = interquartile range. * Based upon physician review of initial report and available documentation, 

including death certificates. † Cardiomyopathy, congestive heart failure, acute leukemia, renal failure/end stage renal disease, general decompensation/end stage disease. 
Reports to VAERS of co-administration of COVID-19 and 

other vaccines

 Most common vaccines co-administered with COVID-19 vaccines*

• Vaccine not specified (n = 442)

• Influenza (total = 204; inactivated = 127)

• Zoster (n = 61)

 Most commonly reported adverse events

• Typically “extra dose” or “expired product” administered

• Systemic symptoms: reflect known adverse events (headache, fatigue, fever, etc.)

• Unique to zoster: “herpes zoster”, “vaccination failure”

 Surveillance for adverse events is ongoing

Includes data collected during December 14, 2020–October 10, 2021. 

* 605,095 reports were of COVID-19 vaccine with no other vaccine administered
Active safety monitoring for COVID-19 vaccines

v-safe is a CDC smart phone-based monitoring program for COVID-19 

vaccine safety in the U.S.

• Uses text messaging and web surveys to check in with vaccine recipients after 

vaccination

• Can register at any time: after first, second, or third dose

• Solicits participants' reports on how they feel after COVID-19 vaccination

• Local injection site reactions (i.e., pain, redness, swelling)

• Systemic reactions (i.e., fatigue, headache, joint pain)

• Health impacts (unable to perform normal daily activities, missed school 

or work, or received care) 

12
Smartphone-based active safety monitoring

13

Key strengths

 Easy and quick

 Active outreach

 Longitudinal data

Key limitations

 Voluntary enrollment

 Requires smartphone 

 Generally, cannot determine 

cause and effect
Demographic summary of 274,167 v-safe participants who 

reported an additional dose

Includes participants who completed at least one survey in the first week after additional dose, data collected during August 12–October 10, 2021

Abbreviations: AI/AN = American Indian/Alaska Native; NHPI = Native Hawaiian or other Pacific Islander; AA=African American.

Characteristic % of participants

Sex

Female 61.8

Male 37.3

Unknown 0.9

Age group (years)

0-17 0.05

18-49 26.6

50-64 23.0

65-74 38.9

75-84 10.5

≥85 0.9

Characteristic % of participants

Ethnicity

Hispanic or Latino 6.3

Not Hispanic/ Latino 90.1

Unknown 3.5

Race

AI/AN 0.4

Asian 5.6

Black or AA 5.0

NHPI 0.3

White 83.7

Multiracial 1.4

Other 1.8

Unknown 1.9

14
Patterns of vaccination for 274,167 v-safe participants who 

reported an additional dose

Moderna (%) Pfizer-BioNTech (%) Janssen (%)* Total

Moderna 13,719 (98.5) 583 89 14,391

Pfizer-BioNTech 207 259,327 (>99.9) 83 259,617

Janssen 7 70 82 (32.3) 159

Total 13,933 259,980 254 274,167

Primary series

Additional

dose

Includes participants who completed at least one survey in the first week after additional dose, data collected during August 12–October 10, 2021

* Includes persons who received Janssen as their primary series and one additional dose of vaccine from the listed manufacturers 15
Top 10 solicited reactions reported at least once 0-7 days after 

dose 3 of Moderna or Pfizer-BioNTech vaccine

Includes 273,046 participants who completed at least one survey in the first week after additional dose, data collected during August 12–October 10, 2021

0

10

20

30

40

50

60

70

80

90

100

Pain -

injection site

Fatigue Myalgia Headache Fever Swelling -

injection site

Joint pain Chills Redness Nausea

Percentage

Moderna Pfizer-BioNTech

16
Reactions and health impact events reported at least once in days 0-7 

after Pfizer-BioNTech vaccination, by dose

Includes 188,514 participants who completed at least one survey in the first week after each dose, data collected during August 12–October 10, 2021 

* Dose 2 compared to dose 3: statistically significant difference (p-value <0.05) using multivariable generalized estimating equations model that accounted for 

the correlation between registrants and adjusted for demographic variables. 17

0

10

20

30

40

50

60

70

80

90

100

Any injection site

reaction

Any systemic reaction Any health impact Unable to perform

daily activities

Unable to work Needed medical care

Percentage

Dose 1 Dose 2 Dose 3

* *

* *

*

*
Reactions and health impact events reported at least once in days 0-7 

after Moderna vaccination, by dose

Includes 8,153 participants who completed at least one survey in the first week after each dose, data collected during August 12–October 10, 2021 

* Dose 2 compared to dose 3: statistically significant difference (p-value <0.05) using multivariable generalized estimating equations model that accounted for 

the correlation between registrants and adjusted for demographic variables. 18

0

10

20

30

40

50

60

70

80

90

100

Any injection site

reaction

Any systemic reaction Any health impact Unable to perform

daily activities

Unable to work Needed medical care

Percentage

Dose 1 Dose 2 Dose 3

* *

*

*

*
Summary of v-safe 65,247 v-safe participants who reported 

co-administration of COVID-19 and other vaccines

Dose number % of participants

1 6.3

2 3.8

3 89.8

Age group % of participants

0-17 1.4

18-49 31.8

50-64 23.9

65-74 34.2

75-84 8.0

≥85 0.8

 Most (89.9%) participants were aged 18-74 

years

 89.8% of co-administration occurred with 

dose 3 COVID-19 vaccine

 Surveillance is ongoing

Includes 65,247 participants who completed at least one survey in the first week after each dose, data collected during June 19–October 10, 2021. Collection 

of co-administration data in v-safe began June 19, 2021. 19
Limitations of early safety monitoring for an additional 

COVID-19 vaccine dose

 v-safe population likely not representative of the vaccinated U.S. population

 Additional dose recipients likely included immunocompromised and nonimmunocompromised persons

 Approximately half of mRNA third doses are among persons aged ≥65 years

 At this time, data are limited to:

• Determine patterns of adverse events after dose 2 Janssen or an 

additional dose from a manufacturer different from the primary series

• Identify rare adverse events

 Complete medical review of deaths following vaccination reported to VAERS 

is dependent on availability of medical records, death certificates, and 

autopsy reports, which may be delayed or not available

20
Summary

 No unexpected patterns of adverse events were identified

 ≥92% of VAERS reports following dose 3 of COVID-19 vaccination were nonserious

• Vaccination errors and systemic symptoms were most commonly reported

 Over 270,000 v-safe registrants reported an additional dose

• Most reported a primary mRNA vaccine series followed by dose 3 from the 

same manufacturer

• For Pfizer-BioNTech, local and systemic reactions were reported less 

frequently following dose 3 than dose 2

• For Moderna, local reactions were reported slightly more frequently and 

systemic reactions slightly less frequently following dose 3 than dose 2

21

1 https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-initiate-rolling-submission 
Next steps

 VAERS and v-safe will continue to monitor safety of additional doses of 

COVID-19 vaccination

 The Vaccine Safety Datalink (VSD) will incorporate additional doses of 

COVID-19 vaccination into its ongoing safety monitoring

 The Clinical Immunization Safety Assessment (CISA) Project will continue to 

be available to consult on clinically complex adverse events following 

additional dose of COVID-19 vaccination

 CDC will update the Advisory Committee on Immunization Practices (ACIP) 

as additional data become available

22
Acknowledgements  VAERS and v-safe teams  James Baggs  Paige Marquez  John Su  Tanya Myers  David Shay  Tom Shimabukuro  Julianne Gee

23
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

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.

Thank you!