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 calculating the rate ratio 30 days after the second dose as compared with unvaccinated 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 recipients. The clinical presentation of myocarditis after vaccination was usually mild.

中文翻译：

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以色列接种针对 Covid-19 的 BNT162b2 mRNA 疫苗后出现心肌炎

背景

截至 2021 年 5 月 31 日，约 510 万以色列人在接受两剂 BNT162b2 信使 RNA 疫苗（辉瑞 BioNTech）后已对 2019 年冠状病毒病（Covid-19）完全免疫。在不良事件监测期间出现心肌炎的早期报告后，以色列卫生部启动了主动监测。

方法

我们回顾性审查了 2020 年 12 月 20 日至 2021 年 5 月 31 日期间获得的所有心肌炎病例的数据，并使用 Brighton Collaboration 定义对信息进行分类。我们通过计算第一剂和第二剂疫苗接种后（相隔21天）发病率的风险差异来分析心肌炎的发生情况；通过计算第一次给药后 21 天内和第二次给药后 30 天内观察到的发病率与预期发病率的标准化发病率，与诊断的确定性无关；并计算第二次接种后 30 天与未接种疫苗者的比率。

结果

在 304 名出现心肌炎症状的人中，有 21 人接受了替代诊断。其余283例中，142例发生在接种BNT162b2疫苗后；在这些病例中，136 例确诊或可能诊断。129 名接受者 (95%) 的临床表现被判定为轻度；一起严重病例导致死亡。第一剂和第二剂之间的总体风险差异为每 100,000 人 1.76（95% 置信区间 [CI]，1.33 至 2.19），其中 16 至 19 岁之间的男性接受者之间的差异最大（差异为每 100,000 人 13.73）人；95% CI，8.11 至 19.46）。与基于历史数据的预期发病率相比，标准化发病率为 5.34（95% CI，4.48 至 6.40），并且在 16 岁至 19 岁之间的男性受者中第二剂接种后最高（13.60；95% CI） ，9.30 至 19.20）。与未接种疫苗的人相比，第二次疫苗接种后 30 天的比率为 2.35（95% CI，1.10 至 5.02）；16 至 19 岁男性受助者的比率再次最高（8.96；95% CI，4.50 至 17.83），比率为 1:6637。

结论

心肌炎的发病率虽然较低，但在接受 BNT162b2 疫苗后有所增加，特别是在年轻男性接种者中接种第二剂后。接种疫苗后心肌炎的临床表现通常较轻微。