Table 1.

Incidence of myocarditis and pericarditis following Covid-19 mRNA vaccines

	Country	Period of observation	Administered doses	Demographics	Cases of myocarditis and pericarditis	Groups at risk
Klein et al. [9]	US	14 Dec 2020 to 26 June 2021	11,845,128 doses in 6.2 million individuals, 57% BNT162b2, 43% mRNA-1273, 6,175,813 first doses and 5,669,315 second doses	Mean age 49, 54% female	87 cases of myocarditis and pericarditis (131.7 events/million person-years), adjusted rate ratio 1.18 (95% CI, 0.79–1.79)	34 cases in the age category 12–39 years, 85% male, 29 cases within 7 days of vaccine (321 events/million person-years), adjusted RR 9.83 (95% CI, 3.35–35.77)
Diaz et al. [10]	US	Feb to May 2021	2,000,287 individuals, 52.6% BNT162b2, 44.1% mRNA-1273	Median age 57, 59% female	20 cases of myocarditis (1.0 per 100,000 persons [95% CI, 0.61–1.54]), 37 cases of pericarditis (1.8 per 100,000 [95% CI, 1.30–2.55])	Myocarditis 75% men, median age 36 years, pericarditis 73% men, median age 59 years
Barda et al. [7]	Israel	20 Dec 2020 to 24 May 2021	938,812 doses of BNT162b2	Median age 38, 48% female	21 cases of myocarditis, risk ratio 3.24 (95% CI, 1.55–12.44), risk difference 2.7 events per 100,000 (95% CI, 1.0–4.6)	Most cases were males and the median age was 25 years
Mevorach et al. [11]	Israel	20 Dec 2020 to 31 May 2021	9,289,765 doses of BNT162b2,5,442,696 individuals received a first vaccine dose and 5,125,635 received two doses	N/A	136 cases of definite or probable myocarditis, standardized incidence ratio 5.34 (95% CI, 4.48–6.40), rate ratio 2.35 (95% CI, 1.10–5.02)	Mostly males in young age groups, rate ratio of 8.96 (95% CI, 4.50–17.83) for those between 16 and 19 years, 6.13 (95% CI, 3.16–11.88) for those 20–24
Witberg et al. [12]	Israel	20 Dec 2020 to 24 May 2021	2,558,421 individuals with at least one dose of BNT162b2	Median age 44, 51% female	54 cases of myocarditis (41 mild, 12 intermediate, and 1 fulminant), estimated incidence of 2.13 per 100,000 persons (95% CI, 1.56–2.70)	Incidence particularly high among male patients between 16–29 years (10.69 cases per 100,000 persons; 95% CI, 6.93–14.46)
Data from PHE [13]	UK	Until 28 July 2021	BNT162b2: 20.46 million first and 13.8 million second doses, ChAdOx1 nCov-19: 24.8 million first and 23.6 million second doses, mRNA-1273:1.3 million first doses	N/A	BNT162b2:4.3 myocarditis cases per million doses and 3.8 pericarditis cases per million doses, ChAdOx1 nCov-19:1.7 myocarditis cases per million doses and 3.0 pericarditis cases per million doses, mRNA-1273:14.7 myocarditis cases per million doses and 13.0 pericarditis cases per million doses	N/A
Data from NIPH [14]	Norway	2 Dec 2020 to 6 Oct 2021	7.8 million doses, nearly 4.2 million first doses, thereof 3,490,657 BNT162b2 and 540,248 mRNA-1273, 3.7 million second doses	51% female	173 pericarditis cases (59 women and 114 men, 131 with BNT162b2, 36 with mRNA-1273, 3 with ChAdOx1 nCov-19), 95 myocarditis cases (23 women and 72 men, 52 with BNT162b2, 40 with mRNA-1273)	53.7% of myocarditis cases in individuals <30 years, The pericarditis cases were more evenly divided across the age categories

PHE, Public Health England; NIPH, Norwegian Institute of Public Health; BNT 162b2, Comirnaty − Covid-19 vaccine developed by BioNTech; mRNA-1273, Spikevax − Covid-19 vaccine developed by Moderna; ChAdOx1 nCov-19, Vaxzevria − Covid-19 vaccine developed by AstraZeneca.