The  authors’  full  names,  academic  de-
grees, and affiliations are listed in the Ap-
pendix.  Dr.  Mevorach  can  be  contacted 
at   mevorachd@  gmail . com  or  at  Hadas-
sah  Hebrew  University  Medical  Center. 
Dr.  Alroy-Preis  can  be  contacted  at 
 sharon . alroy@  moh . gov . il or at the Israeli 
Ministry of Health.

Drs. Mevorach and Anis, Ms. Cedar and 
Dr.  Bromberg,  and  Drs.  Keinan-Boker 
and  Alroy-Preis  contributed  equally  to 
this article.

This article was published on October 6, 
2021, at NEJM.org.

N Engl J Med 2021;385:2140-9.
DOI: 10.1056/NEJMoa2109730
Copyright © 2021 Massachusetts Medical Society.

Original Article

Myocarditis after BNT162b2 mRNA Vaccine 
against Covid-19 in Israel
D. Mevorach, E. Anis, N. Cedar, M. Bromberg, E.J. Haas, E. Nadir, 
S. Olsha-Castell, D. Arad, T. Hasin, N. Levi, R. Asleh, O. Amir, K. Meir, D. Cohen, 
R. Dichtiar, D. Novick, Y. Hershkovitz, R. Dagan, I. Leitersdorf, R. Ben-Ami, I. Miskin, 
W. Saliba, K. Muhsen, Y. Levi, M.S. Green, L. Keinan-Boker, and S. Alroy-Preis  

A BS T R AC T

BACKGROUND
Approximately 5.1 million Israelis had been fully immunized against coronavirus 
disease 2019 (Covid-19) after receiving two doses of the BNT162b2 messenger RNA 
vaccine (Pfizer–BioNTech) by May 31, 2021. After early reports of myocarditis during 
adverse events monitoring, the Israeli Ministry of Health initiated active surveillance.

METHODS
We retrospectively reviewed data obtained from December 20, 2020, to May 31, 2021, 
regarding  all  cases  of  myocarditis  and  categorized  the  information  using  the 
Brighton Collaboration definition. We analyzed the occurrence of myocarditis by 
computing the risk difference for the comparison of the incidence after the first 
and second vaccine doses (21 days apart); by calculating the standardized incidence 
ratio of the observed-to-expected incidence within 21 days after the first dose and 
30 days after the second dose, independent of certainty of diagnosis; and by cal-
culating the rate ratio 30 days after the second dose as compared with unvacci-
nated persons.

RESULTS
Among 304 persons with symptoms of myocarditis, 21 had received an alternative 
diagnosis. Of the remaining 283 cases, 142 occurred after receipt of the BNT162b2 
vaccine;  of  these  cases,  136  diagnoses  were  definitive  or  probable.  The  clinical 
presentation was judged to be mild in 129 recipients (95%); one fulminant case 
was fatal. The overall risk difference between the first and second doses was 1.76 
per 100,000 persons (95% confidence interval [CI], 1.33 to 2.19), with the largest 
difference among male recipients between the ages of 16 and 19 years (difference, 
13.73 per 100,000 persons; 95% CI, 8.11 to 19.46). As compared with the expected 
incidence  based  on  historical  data,  the  standardized  incidence  ratio  was  5.34 
(95% CI, 4.48 to 6.40) and was highest after the second dose in male recipients 
between the ages of 16 and 19 years (13.60; 95% CI, 9.30 to 19.20). The rate ratio 
30 days after the second vaccine dose in fully vaccinated recipients, as compared 
with unvaccinated persons, was 2.35 (95% CI, 1.10 to 5.02); the rate ratio was again 
highest in male recipients between the ages of 16 and 19 years (8.96; 95% CI, 4.50 
to 17.83), with a ratio of 1 in 6637.

CONCLUSIONS
The  incidence  of  myocarditis,  although  low,  increased  after  the  receipt  of  the 
BNT162b2 vaccine, particularly after the second dose among young male recipi-
ents. The clinical presentation of myocarditis after vaccination was usually mild.

2140

n engl j med 385;23  nejm.org  December 2, 2021

T h e  n e w   e ng l a n d   j o u r na l   o f  m e dic i n e

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Myocarditis after BNT162b2 Vaccine against Covid-19

A fter the emergency use authoriza-

tion  of  the  BNT162b2  messenger  RNA 
(mRNA) vaccine (Pfizer–BioNTech) against 
coronavirus disease 2019 (Covid-19) by the Food 
and Drug Administration,1 authorization was also 
granted for use in Israel. On December 20, 2020, 
a national vaccination campaign was initiated that 
was based on a two-dose regimen spaced 21 days 
apart.2 The campaign initially targeted health care 
workers and persons who were 60 years of age 
or older, and later the vaccine was offered to all 
persons  who  were  at  least  16  years  of  age.  By 
May 31, 2021, approximately 5.12 million Israeli 
residents had received two vaccine doses.

At the beginning of the vaccination campaign, 
a program of passive surveillance was initiated 
for the monitoring of adverse events within 21 days 
after the first dose of vaccine and within 30 days 
after the second dose. Health care providers re-
ported these data to the Ministry of Health, as 
required by Israeli law. After receipt of reports of 
myocarditis, the Ministry of Health subsequent-
ly initiated active surveillance beginning in Feb-
ruary 2021 by requesting that all hospitals report 
cases  of  myocarditis,  including  cases  that  had 
been  diagnosed  since  December  2020,  with  or 
without  pericardial  effusion  and  regardless  of 
vaccination status. Since persons with suspected 
myocarditis  are  almost  always  hospitalized  in 
Israel, such surveillance data should approximate 
all cases of myocarditis during the period of active 
surveillance.

The aims of the current study were to present 
the clinical and epidemiologic characteristics and 
follow-up findings of cases of myocarditis that 
were diagnosed in temporal proximity to vaccina-
tion and to examine a possible causal relationship 
between the vaccine and myocarditis.

Me thods

Data Source and Case Definition
We retrospectively reviewed data regarding pre-
sumptive cases of myocarditis, including clinical 
and laboratory data and discharge summaries, 
from medical records obtained from the Minis-
try of Health database. The focus of the study was 
the 6 months from December 2020 through May 
2021, which included periods of both active and 
passive surveillance. We used the codes for myo-
carditis (422.0-9x and 429.0x) of the International 
Classification  of  Diseases,  9th  Revision  (ICD-9),  for 
screening. Records were reviewed by one of four 

board-certified cardiologists, with advice from a 
board-certified rheumatologist for verification of 
the diagnosis of myocarditis. All the reviewers 
were aware of the vaccination status of the pa-
tients.

The  diagnostic  criteria  for  myocarditis  and 
degree  of  certainty  of  diagnosis  were  adapted 
from the case definition and classification of the 
Brighton  Collaboration  (Pandemic  Emergency 
Response  Process).3  Cases  were  classified  as 
definitive,  probable,  possible,  having  insuffi-
cient  data,  or  having  an  alternative  diagnosis. 
Cases of pericarditis with myocarditis were in-
cluded among these cases, although pericarditis 
alone was not included in case counts. We also 
compared  the  classification  according  to  the 
Brighton  Collaboration  with  classifications  of 
myocarditis  issued  by  the  Centers  for  Disease 
Control and Prevention (CDC) for adverse events 
after smallpox vaccination.4-6 Additional details 
regarding the two classification systems are pro-
vided in the Methods section and Table S1 in the 
Supplementary Appendix, available with the full 
text of this article at NEJM.org.

Since the study was conducted as part of on-
going clinical surveillance for side effects related 
to the BNT162b2 vaccine as required by national 
guidelines, it received a waiver for review by an 
institutional review board. Pfizer–BioNTech had 
no role in the collection or analysis of the data or 
in the reporting of the data in this study.

Statistical Analysis
We  used  descriptive  frequencies,  percentages, 
means, and standard deviations to characterize 
cases of myocarditis according to age, sex, time 
elapsed since vaccination, length of hospital stay, 
and clinical outcome. Incidence curves were ex-
amined for the occurrence of new cases of myo-
carditis  during  the  first  21  days  after  the  first 
dose  of  vaccine  and  30  days  after  the  second 
dose, since passive surveillance had usually been 
terminated at that point. The data were analyzed 
separately for males and females and according 
to age group (16 to 19 years, 20 to 24 years, 25 to 
29 years, 30 to 39 years, 40 to 49 years, and 50 
years or older). To assess the incidence of myo-
carditis among vaccine recipients, we calculated 
risk differences, observed-to-expected ratios, and 
rate ratios between vaccinated and unvaccinated 
persons.

To calculate the risk difference, we determined 
the risk of myocarditis per 100,000 persons after 

n engl j med 385;23  nejm.org  December 2, 2021

2141

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T h e  n e w   e ng l a n d   j o u r na l   o f  m e dic i n e

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the first and second doses of vaccine according 
to age group and sex. This analysis included only 
the probable or definite myocarditis cases. In the 
calculation  of  the  risk  differences  between  the 
second and first doses, we used the cumulative 
incidence for a follow-up period of 21 days for 
both vaccine doses; we computed 95% confidence 
intervals for the risk difference using the Jeffreys–
Perks method. The percentage of the myocarditis 
risk that could be attributed to the second dose 
was calculated by dividing the risk difference be-
tween the two vaccine doses by the risk after the 
second dose and expressing the quotient as a per-
centage.

We compared the observed incidence of myo-
carditis with the expected incidence using data 
obtained during the period from 2017 through 
2019 in the pre–Covid-19 pandemic era by calcu-
lating standardized incidence ratios (after adjust-
ment for age and sex) for all reported cases of 
myocarditis.  We  performed  this  analysis  in  all 
myocarditis cases that had occurred in temporal 
proximity to the vaccination without accounting 
for the adjudicated category of certainty, because 
historical cases of myocarditis had not been adju-
dicated by a team of clinical experts. We calcu-
lated approximate 95% confidence intervals for 
the true standardized incidence ratio by apply-
ing the Wilson and Hilferty approximation for 
chi-square percentiles.7 In addition, to determine 
whether the standardized incidence ratios could 
have  been  overestimated  owing  to  the  overre-
porting of myocarditis cases because of a higher 
index  of  clinical  suspicion  during  the  surveil-
lance period, we performed a sensitivity analysis 
in which we determined the minimal number of 
observed cases that would be needed to produce 
a significant difference in the standardized inci-
dence ratios for male recipients after the second 
vaccine dose. This subgroup was chosen post hoc 
according  to  the  apparent  increase  in  risk  ob-
served in male teenagers and young adults.

We  compared  the  incidence  of  myocarditis 
among recipients 30 days after the second vaccine 
dose with the incidence among unvaccinated per-
sons starting on January 11, 2021 (when second 
vaccine doses were first administered in Israel) 
up to May 31, 2021, with data reported according 
to age group and sex. We computed the rate ratio 
between vaccinated and unvaccinated persons and 
95%  confidence  intervals  for  each  stratum  and 
for the overall study population after adjustment 

2142

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Myocarditis after BNT162b2 Vaccine against Covid-19

Table 2. Classification of Myocarditis Cases Reported to the Ministry of Health.*

Timing of Myocarditis Diagnosis

Brighton Collaboration Classification of Myocarditis

Level 1

Level 2

Level 3

Level 4

Level 5

All Levels

number of cases

All cases

Vaccinated persons

118

153

≤21 days after first dose and 30 days 

after second dose

>21 days after first dose and 30 days 

after second dose

Unvaccinated persons

55

15

48

81

23

49

3

1

0

2

9

5

2

2

21

9

5

7

304

151

45

108

*  In the Brighton Collaboration classification system for the diagnosis of myocarditis, level 1 indicates definite, level 2 probable, level 3 pos-
sible, level 4 insufficient data, and level 5 ruled out. Included are data for persons who had a delayed second dose of vaccine and who 
received a diagnosis of myocarditis 22 days or longer after the first dose and those in whom myocarditis developed more than 30 days after 
the second dose, so the diagnosis was not considered to have been made in temporal proximity to vaccination.

for age and sex using a negative binomial regres-
sion model. This analysis included only definite 
or probable myocarditis cases (Fig. S1).

Since we had no prespecified plan for adjust-
ment  of  the  width  of  confidence  intervals  for 
multiple comparisons in any of these approaches, 
no definite conclusions can be drawn from these 
data. We also assessed our findings according to 
the Bradford Hill causality criteria.

R e sult s

Cases of Myocarditis
Among 9,289,765 Israeli residents who were in-
cluded during the surveillance period, 5,442,696 
received  a  first  vaccine  dose  and  5,125,635  re-
ceived two doses (Table 1 and Fig. S2). A total of 
304 cases of myocarditis (as defined by the ICD-9 
codes for myocarditis) were reported to the Min-
istry of Health (Table 2). These cases were diag-
nosed  in  196  persons  who  had  received  two 
doses of the vaccine: 151 persons within 21 days 
after the first dose and 30 days after the second 
dose and 45 persons in the period after 21 days 
and  30  days,  respectively.  (Persons  in  whom 
myocarditis developed 22 days or more after the 
first dose of vaccine or more than 30 days after 
the  second  dose  were  considered  to  have  myo-
carditis  that  was  not  in  temporal  proximity  to 
the vaccine.) After a detailed review of the case 
histories, we ruled out 21 cases because of rea-
sonable alternative diagnoses. Thus, the diagnosis 
of myocarditis was affirmed for 283 cases. These 

cases  included  142  among  vaccinated  persons 
within 21 days after the first dose and 30 days 
after the second dose, 40 among vaccinated per-
sons  not  in  proximity  to  vaccination,  and  101 
among unvaccinated persons. Among the unvac-
cinated  persons,  29  cases  of  myocarditis  were 
diagnosed in those with confirmed Covid-19 and 
72 in those without a confirmed diagnosis.

Of the 142 persons in whom myocarditis de-
veloped  within  21  days  after  the  first  dose  of 
vaccine or within 30 days after the second dose, 
136 received a diagnosis of definite or probable 
myocarditis, 1 received a diagnosis of possible 
myocarditis, and 5 had insufficient data. Classifi-
cation  of  cases  according  to  the  definition  of 
myocarditis  used  by  the  CDC4-6  is  provided  in 
Table S1.

Endomyocardial  biopsy  samples  that  were 
obtained from 2 persons showed foci of endoin-
terstitial  edema  and  neutrophils,  along  with 
mononuclear-cell infiltrates (monocytes or mac-
rophages and lymphocytes) with no giant cells. 
No  other  patients  underwent  endomyocardial 
biopsy. The clinical features of myocarditis after 
vaccination are provided in Table S3.

In the 136 cases of definite or probable myo-
carditis,  the  clinical  presentation  in  129  was 
generally mild, with resolution of myocarditis in 
most cases, as judged by clinical symptoms and 
inflammatory  markers  and  troponin  elevation, 
electrocardiographic and echocardiographic nor-
malization, and a relatively short length of hos-
pital stay. However, one person with fulminant 

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T h e  n e w   e ng l a n d   j o u r na l   o f  m e dic i n e

myocarditis died. The ejection fraction was nor-
mal  or  mildly  reduced  in  most  persons  and  se-
verely reduced in 4 persons. Magnetic resonance 
imaging  that  was  performed  in  48  persons 
showed findings that were consistent with myo-
carditis  on  the  basis  of  at  least  one  positive 
T2-based  sequence  and  one  positive  T1-based 
sequence (including T2-weighted images, T1 and 
T2 parametric mapping, and late gadolinium en-
hancement). Follow-up data regarding the status 
of  cases  after  hospital  discharge  and  consistent 
measures of cardiac function were not available.

The peak number of cases with proximity to 
vaccination occurred in February and March 2021; 
the associations with vaccination status, age, and 
sex are provided in Table 1 and Figure 1. Of 136 
persons  with  definite  or  probable  myocarditis, 
19 presented after the first dose of vaccine and 
117 after the second dose. In the 21 days after the 
first dose, 19 persons with myocarditis were hos-
pitalized, and hospital admission dates were ap-
proximately equally distributed over time. A total 
of 95 of 117 persons (81%) who presented after 
the second dose were hospitalized within 7 days 
after vaccination. Among 95 persons for whom 
data regarding age and sex were available, 86 (91%) 
were male and 72 (76%) were under the age of 
30 years.

Comparison of Risks According to First  
or Second Dose

A comparison of risks over equal time periods of 
21 days after the first and second doses accord-
ing to age and sex is provided in Table 3. Cases 
were clustered during the first few days after the 
second  dose  of  vaccine,  according  to  visual  in-
spection of the data (Fig. 1B and 1D). The overall 
risk difference between the first and second doses 
was  1.76  per  100,000  persons  (95%  confidence 
interval [CI], 1.33 to 2.19); the overall risk differ-
ence was 3.19 (95% CI, 2.37 to 4.02) among male 
recipients and 0.39 (95% CI, 0.10 to 0.68) among 
female recipients. The highest difference was ob-
served among male recipients between the ages of 
16 and 19 years: 13.73 per 100,000 persons (95% 
CI, 8.11 to 19.46); in this age group, the percent 
attributable  risk  to  the  second  dose  was  91%. 
The difference in the risk among female recipi-
ents between the first and second doses in the 
same  age  group  was  1.00  per  100,000  persons 
(95% CI, −0.63 to 2.72). Repeating these analy-

Figure 1 (facing page). Timing and Distribution of  
Myocarditis after Receipt of the BNT162b2 Vaccine.
Shown is the timing of the diagnosis of myocarditis 
among recipients of the first dose of vaccine (Panel A) 
and the second dose (Panel B), according to sex, and 
the distribution of cases among recipients according 
to both age and sex after the first dose (Panel C) and 
after the second dose (Panel D). Cases of myocarditis 
were reported within 21 days after the first dose and 
within 30 days after the second dose.

ses with a shorter follow-up of 7 days owing to 
the presence of a cluster that was noted after the 
second vaccine dose disclosed similar differences 
in male recipients between the ages of 16 and 19 
years (risk difference, 13.62 per 100,000 persons; 
95% CI, 8.31 to 19.03). These findings pointed to 
the first week after the second vaccine dose as the 
main risk window.

Observed versus Expected Incidence
Table 4 shows the standardized incidence ratios 
for  myocarditis  according  to  vaccine  dose,  age 
group, and sex, as projected from the incidence 
during  the  prepandemic  period  from  2017 
through 2019. Myocarditis after the second dose 
of vaccine had a standardized incidence ratio of 
5.34  (95%  CI,  4.48  to  6.40),  which  was  driven 
mostly by the diagnosis of myocarditis in young-
er  male  recipients.  Among  boys  and  men,  the 
standardized incidence ratio was 13.60 (95% CI, 
9.30  to  19.20)  for  those  16  to  19  years  of  age, 
8.53 (95% CI, 5.57 to 12.50) for those 20 to 24 
years, 6.96 (95% CI, 4.25 to 10.75) for those 25 
to 29 years, and 2.90 (95% CI, 1.98 to 4.09) for 
those  30  years  of  age  or  older.  These  substan-
tially increased findings were not observed after 
the first dose. A sensitivity analysis showed that 
for male recipients between the ages of 16 and 
24 years who had received a second vaccine dose, 
the observed standardized incidence ratios would 
have required overreporting of myocarditis by a 
factor of 4 to 5 on the assumption that the true 
incidence would not have differed from the ex-
pected incidence (Table S4).

Rate Ratio between Vaccinated and 
Unvaccinated Persons

Within 30 days after receipt of the second vaccine 
dose in the general population, the rate ratio for 
the comparison of the incidence of myocarditis 

2144

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Myocarditis after BNT162b2 Vaccine against Covid-19

A Timing of 19 Cases of Myocarditis after First Vaccine Dose, According to Sex

Men and Boys

Women and Girls

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C Distribution of 19 Cases of Myocarditis after First Vaccine Dose, According to Age and Sex

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D Distribution of 117 Cases of Myocarditis after Second Vaccine Dose, According to Age and Sex

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n engl j med 385;23  nejm.org  December 2, 2021

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T h e  n e w   e ng l a n d   j o u r na l   o f  m e dic i n e

 
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2146

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Myocarditis after BNT162b2 Vaccine against Covid-19

Table 4. Standardized Incidence Ratios for 151 Cases of Myocarditis, According to Vaccine Dose, Age, and Sex.

Age and Sex

First Dose

Second Dose

Observed 
Cases

Expected Cases 
per 2017–2019 
Reference*

Standardized 
Incidence Ratio 
(95% CI)

Observed 
Cases

Expected Cases 
per 2017–2019 
Reference*

Standardized 
Incidence Ratio 
(95% CI)

number

number

All recipients†

25

17.55

1.42 (0.92–2.10)

126

23.43

5.34 (4.48–6.40)

16–19 yr

20–24 yr

25–29 yr

Male

Female

Male

Female

Male

Female

Male

Female

≥30 yr

3

0

5

1

3

0

10

3

1.86

0.23

2.33

0.42

2.17

0.30

8.13

2.11

1.62 (0.32–4.72)

2.14 (0.69–5.00)

2.37 (0.03–13.20)

1.39 (0.28–4.05)

0

0

1.23 (0.59–2.26)

1.42 (0.29–4.15)

32

2

26

6

20

1

32

7

2.35

0.30

3.05

0.56

2.87

0.39

13.60 (9.30–19.20)

6.74 (0.76–24.35)

8.53 (5.57–12.50)

10.76 (3.93–23.43)

6.96 (4.25–10.75)

2.54 (0.03–14.14)

11.04

2.87

2.90 (1.98–4.09)

2.44 (0.98–4.09)

*  Reference data regarding the background incidence of myocarditis were extracted from the Israel National Hospital Discharge Database for 

the years 2017 through 2019.

†  Data are listed for the 151 vaccine recipients in whom myocarditis was diagnosed at any level of certainty within 21 days after the first dose 

and 30 days after the second dose; data for all vaccine recipients have been weighted according to age and sex.

between  vaccinated  and  unvaccinated  persons 
was 2.35 (95% CI, 1.10 to 5.02) according to the 
Brighton Collaboration classification of definite 
and probable cases and after adjustment for age 
and  sex.  This  result  was  driven  mainly  by  the 
findings for males in younger age groups, with 
a  rate  ratio  of  8.96  (95%  CI,  4.50  to  17.83)  for 
those between the ages of 16 and 19 years, 6.13 
(95% CI, 3.16 to 11.88) for those 20 to 24 years, 
and 3.58 (95% CI, 1.82 to 7.01) for those 25 to 
29 years (Table 5). When follow-up was restrict-
ed to 7 days after the second vaccine dose, the 
analysis results for male recipients between the 
ages of 16 and 19 years were even stronger than 
the  findings  within  30  days  (rate  ratio,  31.90; 
95%  CI,  15.88  to  64.08).  Concordance  of  our 
findings with the Bradford Hill causality criteria 
is shown in Table S5.

Discussion

During a nationwide vaccination campaign con-
ducted from December 2020 through May 2021 
involving  more  than  5  million  residents,  the 

Israeli Ministry of Health recorded 136 cases of 
definite  or  probable  myocarditis  that  had  oc-
curred  in  temporal  proximity  to  the  receipt  of 
two doses of the BNT162b2 mRNA vaccine — a 
risk  that  was  more  than  twice  that  among  un-
vaccinated persons. This association was highest 
in  young  male  recipients  within  the  first  week 
after the second dose. In our study, definite or 
probable cases of myocarditis among persons be-
tween the ages of 16 and 19 years within 21 days 
after  the  second  vaccine  dose  occurred  in  ap-
proximately 1 of 6637 male recipients and in 1 of 
99,853 female recipients.

In most cases, symptoms of myocarditis de-
veloped within a few days after the second dose 
of vaccine. The incidence of myocarditis declined 
as the number of newly vaccinated persons de-
creased  over  time.  This  finding  was  suggestive 
of  a  possible  causal  relationship  between  two 
doses of the vaccine and the risk of myocarditis. 
Overall,  we  estimated  that  definite  or  probable 
cases of myocarditis occurred in the overall Israeli 
population at a rate of approximately 1 per 26,000 
males and 1 per 218,000 females after the sec-

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T h e  n e w   e ng l a n d   j o u r na l   o f  m e dic i n e

Table 5. Rate Ratios for a Diagnosis of Myocarditis within 30 Days after the Second Dose of Vaccine, as Compared with Unvaccinated 
Persons (January 11 to May 31, 2021).

Age and Sex

Vaccinated Group

Unvaccinated Group

Rate Ratio 
(95% CI)

Person-Days  
of Follow-up

Cases

Person-Days  
of Follow-up

Cases

number

All recipients*

149,786,065

117

296,377,727

2.35 (1.10–5.02)

16–19 yr

20–24 yr

25–29 yr

Male

Female

Male

Female

Male

Female

Male

Female

≥30 yr

6,018,541

6,033,192

7,088,335

6,889,399

6,590,263

6,417,564

53,577,403

57,171,368

31

2

27

5

18

1

26

7

19,135,706

17,768,696

20,926,320

20,832,407

20,944,595

20,943,920

82,419,957

93,406,126

*  Data for all vaccine recipients have been weighted according to age and sex.

98

11

2

13

2

16

0

40

14

8.96 (4.50–17.83)

2.95 (0.42–20.91)

6.13 (3.16–11.88)

7.56 (1.47–38.96)

3.58 (1.82–7.01)

0

1.00 (0.61–1.64)

0.82 (0.33–2.02)

ond  vaccine  dose,  with  the  highest  risk  again 
among  young  male  recipients.  This  result  may 
explain why a phase 3 trial of the vaccine, which 
included only 15,000 male and female recipients,8 
showed no cases of myocarditis. The mechanism 
of vaccine-induced myocarditis is not known but 
may  be  related  to  the  active  component  of  the 
vaccine, the mRNA sequence that codes for the 
spike protein of severe acute respiratory syndrome 
coronavirus  2  (SARS-CoV-2),  or  to  the  immune 
response that follows vaccination.

Although selection bias in this study is pos-
sible, we consider it unlikely, since we used data 
from the entire nation. A major limitation of the 
study  is  that  the  calculation  of  rate  ratios  was 
based on individual patient data in the vaccinated 
group as compared with aggregated data in the 
unvaccinated group. In addition, the diagnosis of 
myocarditis was not validated by myocardial bi-
opsy, and acquisition bias could be present, be-
cause  clinical  assessors  were  aware  of  vaccina-
tion status. Misclassification may have taken place 
during surveillance, which could have resulted in 
the underdiagnosis of myocarditis among young 
patients with chest pain or discomfort who were 
not  referred  for  evaluation  for  myocarditis  be-

cause of a low level of suspicion, despite notifi-
cations by the Ministry of Health to health care 
providers. There was also a possibility of overdi-
agnosis of cases of myocarditis owing to increased 
public and medical awareness of this possible side 
effect  of  vaccination.  However,  our  sensitivity 
analysis did not support the occurrence of over-
reporting  as  an  explanation  for  our  findings. 
Our calculations of risk difference and rate ratios 
were confined to cases that had met strict criteria 
for definite or probable myocarditis, which would 
tend to reduce ascertainment bias. Another limi-
tation may be the use of the Israel National Hos-
pital Discharge Database for the years 2017 through 
2019 as a reference for the background incidence 
of  myocarditis  in  the  analyses  of  standardized 
incidence ratios. Those years were different from 
the period between 2020 and 2021 with respect 
to  viral  circulation  —  including  influenza  out-
breaks in 2017, 2018, and 2019 but not in 2020 
and  2021  and  Covid-19  morbidity  in  2020  and 
2021 but not in 2017 through 2019 — and to the 
lack of systematic reporting of myocarditis dur-
ing the earlier period. However, hospitalization 
rates  for  myocarditis  during  the  period  from 
2017 through 2019 were similar to those in 2020, 

2148

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Myocarditis after BNT162b2 Vaccine against Covid-19

and the databases used for these denominators 
are representative of the unvaccinated population. 
We were unable to adjust for potential confound-
ers other than age and sex.

Finally, the rates of myocarditis in our study 
can be compared with those in the Clalit Health 
Services database in the study by Witberg et al.,9 
as now reported in the Journal. That study showed 
a somewhat lower incidence of myocarditis, pos-
sibly because of the different methods that were 
used.  In  our  study,  each  vaccination  date  was 
recorded to ensure accurate follow-up of 21 days 
after the first dose and 30 days after the second 
dose, whereas Witberg et al. followed vaccinees 
for 42 days after the first dose. The study design 
may have led to an underestimation of myocar-
ditis cases owing to a shorter follow-up for the 
second dose. In our study, the rate of myocardi-
tis in the general unvaccinated population was 
1 per 10,857 and can be compared with findings 
indicating  that  myocarditis  was  more  common 

after SARS-CoV-2 infection than after vaccination, 
as reported previously by Barda et al.10

On the basis of data from an Israeli national 
database, the incidence of myocarditis after two 
doses of the BNT162b2 mRNA vaccine was low 
but  higher  than  the  incidence  among  unvacci-
nated  persons  and  among  historical  controls. 
The risk of myocarditis was driven primarily by 
the increased incidence after the second dose of 
vaccine and in young male recipients.

Disclosure forms provided by the authors are available with 

the full text of this article at NEJM.org.

We  thank  the  following  members  of  the  safety  committee: 
Alex  Batler,  Bella  Elran,  Michael  Askenazi,  Rina  Mintz,  and 
Yaron Niv; staff members at the medical centers that helped to 
collect the data; Aharona Freedman of the Israel Center for Dis-
ease Control for her contribution to computations of rate ratios; 
Orna Cohen, Rivka Rich, and Michal Ashkenazy of the Division 
of  Epidemiology  and  Bela  Elran  of  the  Public  Health  Services 
at the Ministry of Health for their contributions to data collec-
tion; and the residents of Internal Medicine B of the Hadassah 
Medical Center who made us aware of the association between 
vaccination and myocarditis.

Appendix
The authors’ full names and academic degrees are as follows: Dror Mevorach, M.D., Emilia Anis, M.D., M.P.H., Noa Cedar, M.P.H., 
Michal Bromberg, M.D., M.P.H., Eric J. Haas, M.D., M.S.C.E., Eyal Nadir, M.D., Sharon Olsha-Castell, M.D., Dana Arad, R.N., M.S.N., 
Tal Hasin, M.D., Nir Levi, M.D., Rabea Asleh, M.D., Ph.D., Offer Amir, M.D., Karen Meir, M.D., Dotan Cohen, M.D., Rita Dichtiar, 
M.P.H., Deborah Novick, M.Sc., Yael Hershkovitz, M.Sc., Ron Dagan, M.D., Iris Leitersdorf, M.D., M.H.A., Ronen Ben-Ami, M.D., Ian 
Miskin, M.D., Walid Saliba, M.D., M.P.H., Khitam Muhsen, Ph.D., Yehezkel Levi, M.D., Manfred S. Green, M.B., Ch.B., Ph.D., Lital 
Keinan-Boker, M.D., Ph.D., and Sharon Alroy-Preis, M.D., M.P.H.

The authors’ affiliations are as follows: the Department of Internal Medicine B, Division of Immunology–Rheumatology, and Wohl 
Institute for Translational Medicine (D.M.) and the Departments of Cardiology (R.A., O.A.), Pathology (K. Meir), and Radiology (D.C.), 
Hadassah Medical Center, Braun School of Public Health (E.A.), Jesselson Integrated Heart Center, Shaare Zedek Medical Center (T.H., 
N.L.), and the Department of Family Medicine (I.M.), Faculty of Medicine, Hebrew University of Jerusalem, the Divisions of Epidemiol-
ogy (E.A., N.C., E.J.H., E.N.), Patient Safety (S.O.-C., D.A.), and Medicine (I.L.), Israeli Ministry of Health (M.B., R. Dichtiar, D.N., Y.H., 
Y.L., L.K.-B., S.A.-P.), and Clalit Health Services (E.N., I.M.), Jerusalem, Israel Center for Disease Control, and Azrieli Faculty of Medi-
cine, Bar-Ilan University (O.A.), Ramat Gan, the Department of Epidemiology and Preventive Medicine, School of Public Health (M.B., 
K. Muhsen), and Tel Aviv Sourasky Medical Center (R.B.-A.), Tel Aviv University, Tel Aviv, Ben Gurion University of the Negev, Beer 
Sheva (E.J.H., R. Dagan), and the Department of Community Medicine and Epidemiology, Lady Davis Carmel Medical Center, Tech-
nion–Israel Institute of Technology (W.S.), and the School of Public Health, University of Haifa (M.S.G., L.K.-B.), Haifa — all in Israel.

References
1.  Emergency use authorization: Pfizer-
BioNTech COVID-19 vaccine. Silver Spring, 
MD:  Food and Drug Administration, 2021 
(https://www . fda . gov/  emergency 
- preparedness - and - response/  coronavirus 
- disease - 2019 - covid - 19/  pfizer - biontech 
- covid - 19 - vaccine).
2.  Haas  EJ,  Angulo  FJ,  McLaughlin  JM, 
et al. Impact and effectiveness of mRNA 
BNT162b2  vaccine  against  SARS-CoV-2 
infections and COVID-19 cases, hospitali-
sations,  and  deaths  following  a  nation-
wide  vaccination  campaign  in  Israel:  an 
observational  study  using  national  sur-
veillance data. Lancet 2021; 397: 1819-29.
3.  Brighton  Collaboration.  Myocarditis/
pericarditis  case  definition.  The  Task 
Force  for  Global  Health,  July  16,  2021 

(https://brightoncollaboration . us/ 
 myocarditis - case - definition - update/  ).
4.  Casey C, Vellozzi C, Mootrey GT, et al. 
Surveillance guidelines for smallpox vac-
cine (vaccinia) adverse reactions. MMWR 
Recomm Rep 2006; 55: 1-16.
5.  Centers for Disease Control and Pre-
vention  (CDC).  Update:  cardiac-related 
events during the civilian smallpox vacci-
nation  program  —  United  States,  2003. 
MMWR Morb Mortal Wkly Rep 2003; 52: 
492-6.
6.  Mei R, Raschi E, Forcesi E, Diemberg-
er  I,  De  Ponti  F,  Poluzzi  E.  Myocarditis 
and  pericarditis  after 
immunization: 
gaining insights through the Vaccine Ad-
verse Event Reporting System. Int J Car-
diol 2018; 273: 183-6.

7.  Sahai H, Khurshid A. Statistics in epi-
demiology: methods, techniques, and ap-
plications.  Boca  Raton,  FL:   CRC  Press, 
1996.
8.  Polack FP, Thomas SJ, Kitchin N, et al. 
Safety  and  efficacy  of  the  BNT162b2 
mRNA Covid-19 vaccine. N Engl J Med 
2020; 383: 2603-15.
9.  Witberg  G,  Barda  N,  Hoss  S,  et  al. 
Myocarditis after Covid-19 vaccination in 
a large health care organization. N Engl J 
Med 2021;385:2132-9.
10. Barda  N,  Dagan  N,  Ben-Shlomo  Y, 
et  al.  Safety  of  the  BNT162b2  mRNA 
Covid-19 vaccine in a nationwide setting.  
N Engl J Med 2021; 385: 1078-90.
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