Table 3.

Characteristics of included cohort studies

Sr. No.	Study design	References	Country reported	Sample size	Age (years)	Gender (M/F)	Follow‐up	Comparator	Experimental group characteristics (vaccine administered)	Outcome	Clinical features	Results
1	Cohort study	Chua et al. 19	Hong Kong	178 163	12–17	(89 806/88 357)	4 months	N/A	Conmirnaty = 305 406 doses administered to 178 163 individuals	Myocarditis = 16 Pericarditis = 2 Perimyocarditi s = 15 Total = 33 After second dose = 27 After first dose = 6	Chest pain = 33 Normal ECG = 6 Normal echocardiogram = 25 Normal CMRI = 7 Mild disease = 33	Incidence rate; myocarditis/pericarditis = 18.52 (95% CI, 11.67–29.09) per 100 000 persons For first dose = 3.37 (95% CI, 1.12–9.51) per 1000 persons Second dose = 21.22 (95% CI, 13.78– 32.28) per 100 000 persons Male = 32.29 (22.78–45.4) per 1000 persons Female = 4.53 (1.76–11.11)
2	Cohort study	Lai et al. 31	Hong Kong, China	252 399	12–18	(138 319/136 565)	28 days	Unvaccinated N = 136 743 M/F = 68 747/67 996 First dose cohort: N = 136 743 Age: 14.15 ± 1.816 12 years = 28 907 13 years = 32 884 14 years = 23 134 15 years = 19 863 16 years = 11 674 17 years = 12 154 18 years = 8127 Second dose cohort: N = 118,300 Age: 14.426 ± 1.799 12 years = 18 235 13 years = 25 355 14 years = 22 885 15 years = 19 871 16 years = 11 677 17 years = 12 153 18 years = 8124	Vaccinated: N = 138 141 M/F = 69 572/68 569 First dose cohort: N = 138 141 Age: 14.17 ± 1.821 12 years = 28 008 13 years = 32 040 14 years = 23 324 15 years = 20 044 16 years = 11 951 17 years = 12 443 18 years = 8331 Second dose cohort: N = 119 664 Age: 14.440 ± 1.803 12 years = 18 300 13 years = 25 461 14 years = 23 091 15 years = 20 063 16 years = 11 954 17 years = 12 455 18 years = 8340 Vaccine administered: Pfizer‐BioNtech	Total cases of Myocarditis: Vaccinated: (n = 38, 0.02%) Unvaccinated: (n = 2, 0.001%) After first dose: Vaccinated: (n = 8, 0.005%) Unvaccinated: (n = 1, 0.0007%) After second dose: Vaccinated: (n = 30, 0.02%) Unvaccinated: (n = 1, 0.0008%)	N/A	Overall Incidence rate of Myocarditis: IRR for first dose cohort: 9.15, 95% CI 1.14–73.16, p = 0.037) IRR for second dose cohort: 29.61 (95% CI 4.04–217.07, p = .0009) Incidence of myocarditis: For first dose: vaccinated = 2.91 (95% CI 1.26–5.73, p = .03) per 100 000 Persons unvaccinated = 0.35 (95% CI; 0.01–2.03) For second dose dose Vaccinated: 12.61 (95% CI 8.51–18.00) per 100 000 vaccinated persons Unvaccinated: 0.42 (95% CI 0.01–2.34) among the unvaccinated.
3	Cohort study	Nygaard et al. 21	Denmark	261 334	12–17	133 477/127 857	N/A	N/A	Vaccine administered: Pfizer‐BioNtech First dose: 261 334 Second dose: Not mentioned	Total cases: N = 15 Male = (n = 13, 87%) Female = (n = 2, 13%) 12 (80%) patients had myocarditis(n = 10) or myopericarditis (n = 2) including 1 meeting the criteria for MIS‐C after vaccination. Pericarditis: (n = 3, 20%)	Chest pain: (n = 15, 100%) Fever: (n = 13, 73%) Elevated CRP: (n = 12, 80%) Abnormal ECG: (n = 9, 60%) Abnormal CMRI: (n = 7, 46%)	The incidence of myopericarditis: 97 males and 16 females per million equaling 1 of 10 000 males and 1 in 63 000 females.
4	Descriptive study	Oster et al. 20	USA	192 405  448	16–31	N/A	N/A	N/A	m‐RNA vaccine dose administered: 354 100 845 Time period between development of symptoms, median (IQR): 2 (1–3)	Myocarditis: 1626 Pericarditis: 684 Myocarditis: BNT162b2 m‐RNA: Male = 1109 Female = 269 After dose 1 = 216 After dose 2 = 1066 After unknown dose = 103 m‐RNA 1273: Male = 447 Female = 156 After dose 1 = 174 After dose 2 = 390 Unknown Ddse = 42 Less than 30 years that met the criteria of diagnosis of myocarditis: Male = 1050 Female = 145 Greater than 30 years: Male = 284 Female = 146 Pericarditis: BNT162b2 m‐RNA: Male = 253 Female = 163 After dose 1 = 111 After dose 2 = 240 After unknown dose = 68 m‐RNA 1273: Male = 155 Female = 107 After dose 1 = 82 After dose 2 = 134 Unknown dose = 49 Less than 30 years pericarditis: N = 148 Greater than 30 years: N = 536	Chest pain = 727/817(89%) Shortness of breath 242/817; (30%) Elevated Troponin levels: 792/809, 98% Abnormal ECG: 569/794, 71% Decrease LVEF: 84/721, 11% Abnormal CMRI: 223/312, 71%	Males comprised 82% (1334/1625) of the myocarditis case. Males aged 12–15 years = 70.7 (95% CI, 61.68–81.11) per million doses of the BNT162b2 vaccine. Males aged 16–17 years = 105.9 (95% CI, 91.65–122.27) per million doses of the BNT162b2 vaccine. Male aged 18–24 years = 52.4 (95% CI, 45.56–60.33) and 56.3 (95% CI, 47.08–67.34) per million doses of the BNT162b2 vaccine and the mRNA 1273 vaccine, respectively.
5	Retrospective Cohort	Witberg et al. 22	Israel	2 558 421	16–≥30	1 248 433/1 309 988	42 days	N/A	BNT162b2(Pfizer/BioNTech) = 2 558 421, all of the participants received first dose whereas 2 401 605 participants received second dose.	Total cases of myocarditis = 54 cases of myocarditis by sex and age: Male sex = 51 Female sex = 3 Either sex, 16–29 years = 32 Either sex ≥ 30 years = 22 Male, 16–29 years = 31 Female, 16–29 years = 1 Male ≥30 years = 20 Female ≥30 years = 2	Mild myocarditis = 41(76%) Intermediate myocarditis = 12 (22%) LVD = 14(26%) chest pain = 44 (81%) Dyspnea = 3 (5.5%) Fever = 5 (9%) Pericardial effusion = 10 (18.5%) ECG changes = 38 (70%) Elevated Troponin T = 41	Cumulative Incidence (95% CI) for all cases of myocarditis: All vaccinated participants: 2.13 (1.6–2.70) Male sex = 4.12 (2.99–5.26) Female sex = 0.23 (0–0.49) Either sex, 16–29 years = 5.49 (3.59–7.39) Either sex ≥30 years = 1.13 (0.66–1.60) Male, 16–29 years = 10.69 (6.93–14.46) Female, 16–29 years = 0.34 (0–1) Male ≥30 years = 2.11 (1.19–3.04) Female ≥30 years = 0.20 (0–0.48)
6	Retrospective cohort study	Mevorach et al. 23	Israel	9 289 765	16–50	2 668 894/2 773 802	183 days	N/A	BNT162b2 (Pfizer/BionTech) = 5 442 696. First dose: 5 442 696, second dose: 5 125 635	Myocarditis: 136, After first dose: 19 After second dose: 117 Male recipients: 16–19 years = 3 20–24 years = 5 25–29 years = 3 30–39 years=2 40–49 years=3 ≥50 years = 1 Female recipients: 16–19 years = 0 20–24 years = 0 25–29 years = 0 30–39 years = 0 40–49 years = 1 ≥50 years = 1	Mild myocarditis: 129 (90.9%) cases Chest pain = 129 (95%) Fever = 63 (46.7%) Dyspnea = 17 (12.5%) ECG changes = 93 (68%) Elevated Troponin I or T = 136 (100%) Elevated C‐reactive protein = 118 (86.7%) LGE = 48 (35%)	Risk of myocarditis per 100 000 persons by age: Male recipients: 16–19 years = 1.34 20–24 years = 1.91 25–29 years = 1.22 30–39 years = 0.41 40–49 years = 0.65 ≥50 years = 0.10 Female recipients: 16–19 years = 0 20–24 years = 0 25–29 years = 0 30–39 years = 0 40‐49 years = 0.21 ≥50 years = 0.09 RD (95% CI) for myocarditis according to age and sex (21 days after first dose): 3.19 (2.37–4.02) Standardized Incidence ratio for myocarditis according to age, sex and dose: 5.34 (4.48–6.40), rate ratio of myocarditis within 30 days after second dose as compared to unvaccinated patients: 2.35 (1.10–5.02)

Abbreviations: CMRI, cardiac magnetic resonance imaging; ECG, electrocardiogram; F, female; IRR, incidence rate ratio; LVEF, left ventricular ejection fraction; M, male; MIS‐C, multiple inflammatory syndrome in children; RD, risk difference.