cdc.gov/coronavirus

Myopericarditis following COVID-19 

vaccination: Updates from the Vaccine 

Adverse Event Reporting System (VAERS) 

Oct 21, 2021

John R. Su, MD, PhD, MPH

Vaccine Safety Team

CDC COVID-19 Vaccine Task Force
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

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Myopericarditis reports to VAERS

3
Reports of myocarditis and myocarditis with pericarditis 

(myopericarditis) following COVID-19 vaccination 

▪ As of Oct 6, 2021, a total of 402,469,096 doses of COVID-19 vaccines were 

administered (Pfizer-BioNTech, Moderna, and Janssen)

• 3,336 reports of myocarditis and pericarditis 

• Myopericarditis: 2,459 reports

• Pericarditis alone: 877 reports

4
Preliminary myopericarditis reports to VAERS following COVID-19 

vaccination, by dose number (data thru Oct 6, 2021)

Manufacturer

Reports after

dose 1 

Reports after 

dose 2

Reports after

unknown dose

Pfizer-BioNTech (n=1,651) 250 1,160 241

Moderna (n=723) 198 419 106

Janssen (n=71) 50 1 20

Not reported (n=14) 1 8 5

Total (N=2,459) 499 1,588 372

▪ Includes total preliminary reports identified through VAERS database searches for reports with myopericarditis MedDRA* codes and 

pre-screened VAERS reports with signs and symptoms consistent with myopericarditis; excludes reports of solely pericarditis

• Follow-up, medical record review, application of CDC working case definition, and adjudication is ongoing or pending

* Medical Dictionary for Regulatory Activities https://www.meddra.org/ 5
Characteristics of preliminary* myopericarditis reports to VAERS 

following known mRNA COVID-19 vaccination†(data thru Oct 6, 2021)

Characteristics

Dose 1 (mRNA only) 

(n=448)†

Dose 2 

(n=1,579)†

Median age, years (IQR**) 28 (19–42) 20 (16–31)

Median time to symptom onset, days (IQR) 3 (1–10) 2 (1–4)

Sex (%)

Male 299 (67%) 1,273 (81%)

Female 142 (32%) 295 (19%)

Not reported/not available 7 (2%) 11 (1%)

* Includes reports identified through VAERS database searches for reports with myopericarditis MedDRA codes, with signs and symptoms consistent with 

myopericarditis, and with dose number documented; and pre-process VAERS reports with follow-up, medical record review, and application of CDC case definition 

for myopericarditis

† Excludes 50 reports after Janssen, and 1 report that did not specify manufacturer after Dose 1; excludes 1 report after Janssen and 8 reports that did not specify 

manufacturer after Dose 2

** IQR = interquartile range 6
Reporting rates of myocarditis (per 1 million doses administered) after 

mRNA COVID-19 vaccines, 7-day risk period (N=935)*

▪ 366,062,239 doses of 

mRNA vaccine 

administered (dose 1 

and dose 2)*

▪ Reporting rates exceed 

background incidence**

• After dose 1 of 

Pfizer (12–17 years) 

and Moderna (18–

24 years)

• After dose 2 of 

Pfizer (12–39 years) 

and Moderna (18–

49 years)

* As of Oct 6, 2021; 935 of 1,181 reports of myocarditis after doses 1 and 2 of mRNA vaccines occurred during days 0–6 after vaccination; reports verified to meet 

case definition by provider interview or medical record review 

** An estimated 1–10 cases of myocarditis per 100,000 person years occurs among people in the United States, regardless of vaccination status; adjusted for the 

7-day risk period, this estimated background is 0.2 to 1.9 per 1 million person 7-day risk period 7

Pfizer Moderna

(All) (All)

Ages Dose 1 Dose 2 Dose 1 Dose 2

12-15 2.3 21.5 0.0 not calculated

16-17 2.8 37.4 0.0 not calculated

18-24 1.2 18.1 3.1 20.7

25-29 0.7 5.7 1.8 11.2

30-39 0.6 2.8 1.4 3.6

40-49 0.2 1.5 0.2 2.1

50-64 0.3 0.4 0.5 0.5

65+ 0.1 0.2 0.0 0.3
Reporting rates (per 1 million doses administered) of myocarditis among 

males after mRNA COVID-19 vaccines, 7-day risk period (N=797)*

* As of Oct 6, 2021; 797 of 935 reports after doses 1 and 2 of mRNA vaccines occurred during Days 0–6 after vaccination among males; reports verified to meet 

case definition by provider interview or medical record review 

** An estimated 1–10 cases of myocarditis per 100,000 person years occurs among people in the United States, regardless of vaccination status; adjusted for the 

7-day risk period, this estimated background is 0.2 to 1.9 per 1 million person 7-day risk period 8

Pfizer Moderna 

(Males) (Males)

Ages Dose 1 Dose 2 Dose 1 Dose 2

12-15 4.2 39.9 0.0 not calculated

16-17 5.7 69.1 0.0 not calculated

18-24 2.3 36.8 6.1 38.5

25-29 1.3 10.8 3.4 17.2

30-39 0.5 5.2 2.3 6.7

40-49 0.3 2.0 0.2 2.9

50-64 0.2 0.3 0.5 0.6

65+ 0.2 0.1 0.1 0.3

▪ 169,740,953 doses of 

mRNA vaccine 

administered to males 

(dose 1 and dose 2) *

▪ Reporting rates exceed 

background incidence**

• After dose 1 of 

Pfizer (12–24 years) 

and Moderna (18–

39 years)

• After dose 2 of 

Pfizer (12–39 years) 

and Moderna (18–

49 years)
Reporting rates (per 1 million doses administered) of myocarditis among 

females after mRNA COVID-19 vaccines, 7-day risk period (N=138)*

* As of Oct 6, 2021; 138 of 935 reports after doses 1 and 2 of mRNA vaccines occurred during Days 0–6 after vaccination among females; reports verified to meet case definition 

by provider interview or medical record review 

** An estimated 1–10 cases of myocarditis per 100,000 person years occurs among people in the United States, regardless of vaccination status; adjusted for the 7-day risk 

period, this estimated background is 0.2 to 1.9 per 1 million person 7-day risk period 9

Pfizer Moderna

(Females) (Females)

Ages Dose 1 Dose 2 Dose 1 Dose 2

12-15 0.4 3.9 0.0 0.0

16-17 0.0 7.9 0.0 0.0

18-24 0.2 2.5 0.6 5.3

25-29 0.2 1.2 0.4 5.7

30-39 0.6 0.7 0.5 0.4

40-49 0.1 1.1 0.2 1.4

50-64 0.3 0.5 0.5 0.4

65+ 0.1 0.3 0.0 0.3

▪ 193,215,313 doses of 

mRNA vaccine 

administered to females 

(dose 1 and dose 2)*

▪ Reporting rates exceed 

background incidence**

• After dose 2 of Pfizer 

(12–24 years) and 

dose 2 Moderna (18–

29 years)
Care and outcomes

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Care and outcomes of preliminary myopericarditis cases reported to 

VAERS after COVID-19 vaccination in persons <29 years old (N=1,640) 

(data thru Oct 6, 2021)

1,640 total preliminary reports

▪ 877 met CDC case definition* 

of myocarditis or 

myopericarditis

▪ 637 under review

Of 877 meeting case definition:

▪ 829 were hospitalized 

• 789 discharged

‒ 607 (77%) known to have 

recovered from symptoms 

at time of report

• 19 still hospitalized (5 in ICU)

• 21 with unknown disposition

▪ 34 were not hospitalized (seen in 

emergency dept., urgent care, 

outpatient clinic, not specified)

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* Gargano JW, Wallace M, Hadler SC, et al. Use of mRNA COVID-19 

Vaccine After Reports of Myocarditis Among Vaccine Recipients: Update 

from the Advisory Committee on Immunization Practices — United 

States, June 2021. MMWR Morb Mortal Wkly Rep 2021;70:977–982.

https://www.cdc.gov/mmwr/volumes/70/wr/pdfs/mm7027e2-H.pdf
Summary

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Summary

▪ 3,336 reports of myopericarditis or pericarditis to VAERS (as of October 6, 2021)

• 2,459 myopericarditis, 877 pericarditis 

▪ Epidemiology of myopericarditis following COVID-19 vaccination similar to 

previously reported updates

• Primarily in younger males, after dose 2 mRNA vaccination, symptom onset clustering 

within several days of vaccination

▪ Limited follow-up information in VAERS case reports suggests most patients 

(77%) symptomatically recover

▪ Reporting rates of myocarditis > background rates for males (12–49 years, 

depending upon dose and manufacturer) and females (after dose 2, 12–29 

years, depending upon manufacturer)

▪ Data subject to limitations of VAERS 13
Acknowledgments

▪ VAERS Team

• VAERS TTS abstraction team

• VAERS Myopericarditis abstraction team

• VAERS Data team

▪ Clinical Immunization Safety Assessment Project

▪ COVID-19 Vaccine Task Force Data Monitoring and Reporting Group

▪ FDA/Center for Biologics Evaluation and Research

Thanks to the many people who made analysis of these data possible:

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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!

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Extra slides

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MedDRA terms to search for myocarditis and pericarditis

Atypical mycobacterium pericarditis Myocarditis 

Autoimmune myocarditis Myocarditis bacterial

Autoimmune pericarditis Myocarditis helminthic 

Bacterial pericarditis Myocarditis infectious 

Coxsackie myocarditis Myocarditis meningococcal 

Coxsackie pericarditis Myocarditis mycotic

Cytomegalovirus myocarditis Myocarditis post infection 

Cytomegalovirus pericarditis Myocarditis septic

Enterovirus myocarditis Pericarditis

Eosinophilic myocarditis Pericarditis adhesive

Hypersensitivity myocarditis Pericarditis constrictive 

Immune-mediated myocarditis Pericarditis helminthic

Pericarditis infective 

Pericarditis mycoplasmal

Pleuropericarditis

Purulent pericarditis

Viral myocarditis

Viral pericarditis

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CDC case definitions of 

probable and confirmed 

myocarditis, pericarditis, 

and myopericarditis

Gargano JW, Wallace M, Hadler SC, et al. Use of mRNA COVID-19 

Vaccine After Reports of Myocarditis Among Vaccine Recipients: Update 

from the Advisory Committee on Immunization Practices — United 

States, June 2021. MMWR Morb Mortal Wkly Rep 2021;70:977–982.

https://www.cdc.gov/mmwr/volumes/70/wr/pdfs/mm7027e2-H.pdf

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Expected vs. Observed cases of myocarditis reported to VAERS after Pfizer-BioNTech

dose 2, 7-day risk period (N=518)*

Age 

group, 

years

Females Males

Cases of 

myopericarditis, 

expected

Cases of 

myopericarditis, 

observed

Cases of 

myopericarditis, 

expected

Cases of 

myopericarditis, 

observed

12–15 0–4 14 1–7 143

16–17 0–2 17 0–4 139

18–24 1–5 12 1–8 152

25–29 0–4 4 1–6 33

30–39 1–14 5 1–13 34

40–49 1–14 8 1–12 13

50–64 2–24 6 2–21 3

65+ 2–23 3 2–18 1

* As of Oct 6, 2021; assumes a 7-day observation window, with 518 of 682 reports after Pfizer-BioNTech dose 2 occurring during Days 0–6 after vaccination; counts from 

reports meeting case definition for myopericarditis; expected estimates for females 12–29 years adjusted to reflect reduced incidence in this age group 19
Expected vs. Observed cases of myocarditis reported to VAERS after Moderna dose 2, 

7-day risk period (N=216)*

Age group, 

years

Females Males

Cases of 

myopericarditis, 

expected

Cases of 

myopericarditis, 

observed

Cases of 

myopericarditis, 

expected

Cases of 

myopericarditis, 

observed

12–15 0 0 0 1

16–17 0 0 0 1

18–24 0–3 14 0–4 89

25–29 0–2 12 0–4 33

30–39 1–9 2 1–8 29

40–49 1–10 7 1–9 13

50–64 2–18 4 2–17 5

65+ 2–23 3 2–19 3

Moderna

vaccine not 

authorized 

in 12-17 y/o

* As of Oct 6, 2021; assumes a 7-day observation window, with 216 of 254 reports after Moderna dose 2 occurring during Days 0–6 after vaccination; counts from reports 

meeting case definition for myopericarditis; expected estimates for females 12–29 years adjusted to reflect reduced incidence in this age group 

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Observed/Expected vs Reporting Rates

▪ Previous observed/expected analyses assumed same background 

incidence*, regardless of age group

• As presented, implied different incidence by age group

▪ Reporting rates (per 100,000 doses administered) more neutral indicator

• Adjusting for time (COVID-19 vaccines in use for 81.10% of a year), reporting rates 

among females < background incidence

• Also adjusting for lower incidence among females**, rates slightly > 

background incidence after dose 2 Moderna among females 18–29 years of age 

* An estimated 1–10 cases of myocarditis per 100,000 person years occurs among people in the United States

**Adjusted by factor of 1.7, estimated background incidence among females ~ 0.5–4.8 per 100,000 person years; 

(Fairweather, D. et al, Curr Probl Cardiol. 2013;38(1):7-46). 
VAERS

key strengths

▪ Rapidly detects potential 

safety problems 

▪ Can detect rare adverse 

events

key limitations

▪ Inconsistent quality and 

completeness of information

▪ Reporting biases

▪ Generally, cannot determine 

cause and effect

VAERS accepts all reports from everyone regardless 

of the plausibility of the vaccine causing the event or 

the clinical seriousness of the event
Adjusting for background rate of myocarditis

▪ 1–10 per 100,000 person years = 10–100 per 1 million person years

▪ 10–100 per 1 million person years x (7 days/365 days per year) = 0.2–1.9 per 

1 million person 7-day period