Background

Limited evidence is available on the real-world effectiveness of the BNT162b2 vaccine against coronavirus disease 2019 (Covid-19) and specifically against infection with the omicron variant among children 5 to 11 years of age.

Methods

Using data from the largest health care organization in Israel, we identified a cohort of children 5 to 11 years of age who were vaccinated on or after November 23, 2021, and matched them with unvaccinated controls to estimate the vaccine effectiveness of BNT162b2 among newly vaccinated children during the omicron wave. Vaccine effectiveness against documented severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and symptomatic Covid-19 was estimated after the first and second vaccine doses. The cumulative incidence of each outcome in the two study groups through January 7, 2022, was estimated with the use of the Kaplan–Meier estimator, and vaccine effectiveness was calculated as 1 minus the risk ratio. Vaccine effectiveness was also estimated in age subgroups.

Results

Among 136,127 eligible children who had been vaccinated during the study period, 94,728 were matched with unvaccinated controls. The estimated vaccine effectiveness against documented infection was 17% (95% confidence interval [CI], 7 to 25) at 14 to 27 days after the first dose and 51% (95% CI, 39 to 61) at 7 to 21 days after the second dose. The absolute risk difference between the study groups at days 7 to 21 after the second dose was 1905 events per 100,000 persons (95% CI, 1294 to 2440) for documented infection and 599 events per 100,000 persons (95% CI, 296 to 897) for symptomatic Covid-19. The estimated vaccine effectiveness against symptomatic Covid-19 was 18% (95% CI, −2 to 34) at 14 to 27 days after the first dose and 48% (95% CI, 29 to 63) at 7 to 21 days after the second dose. We observed a trend toward higher vaccine effectiveness in the youngest age group (5 or 6 years of age) than in the oldest age group (10 or 11 years of age).

Conclusions

Our findings suggest that as omicron was becoming the dominant variant, two doses of the BNT162b2 messenger RNA vaccine provided moderate protection against documented SARS-CoV-2 infection and symptomatic Covid-19 in children 5 to 11 years of age. (Funded by the European Union through the VERDI project and others.)

中文翻译：

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BNT162b2 疫苗对 5 至 11 岁儿童的 Omicron 的有效性

背景

关于 BNT162b2 疫苗针对 2019 年冠状病毒病 (Covid-19)，特别是针对 5 至 11 岁儿童 omicron 变体感染的现实有效性，现有证据有限。

方法

利用以色列最大的医疗保健组织的数据，我们确定了一组在 2021 年 11 月 23 日或之后接种疫苗的 5 至 11 岁儿童，并将他们与未接种疫苗的对照进行匹配，以估计 BNT162b2 在新接种疫苗的人群中的疫苗有效性omicron 波期间的孩子们。在第一剂和第二剂疫苗接种后，评估了疫苗针对已记录的严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 感染和有症状的 Covid-19 的有效性。使用 Kaplan-Meier 估计器估计截至 2022 年 1 月 7 日两个研究组中每种结果的累积发生率，疫苗有效性计算为 1 减去风险比。还按年龄亚组评估了疫苗的有效性。

结果

在研究期间接种疫苗的 136,127 名符合条件的儿童中，有 94,728 名与未接种疫苗的对照组相匹配。首次接种后 14 至 27 天时，针对记录感染的估计疫苗有效性为 17%（95% 置信区间 [CI]，7 至 25），而在接种后 7 至 21 天时，疫苗有效性为 51%（95% CI，39 至 61）第二剂。第二次接种后第 7 至 21 天，研究组之间记录感染的绝对风险差异为每 100,000 人 1905 起事件（95% CI，1294 至 2440），每 100,000 人有 599 起事件（95% CI，296 至 897）针对有症状的 Covid-19。首次接种后 14 至 27 天时，针对有症状的 Covid-19 的估计疫苗有效性为 18%（95% CI，-2 至 34），而在接种后 7 至 21 天时，疫苗有效性为 48%（95% CI，29 至 63）。第二剂。我们观察到，最小年龄组（5 岁或 6 岁）的疫苗有效性高于最大年龄组（10 岁或 11 岁）的趋势。

结论

我们的研究结果表明，随着 omicron 成为主要变体，两剂 BNT162b2 信使 RNA 疫苗为 5 至 11 岁儿童提供了针对已记录的 SARS-CoV-2 感染和有症状的 Covid-19 的适度保护。（由欧盟通过 VERDI 项目和其他项目资助。）