Background

The BNT162b2 vaccine against coronavirus disease 2019 (Covid-19) has been authorized for use in children 5 to 11 years of age and adolescents 12 to 17 years of age but in different antigen doses.

Methods

We assessed the real-world effectiveness of the BNT162b2 vaccine against infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among children and adolescents in Qatar. To compare the incidence of SARS-CoV-2 infection in the national cohort of vaccinated participants with the incidence in the national cohort of unvaccinated participants, we conducted three matched, retrospective, target-trial, cohort studies — one assessing data obtained from children 5 to 11 years of age after the B.1.1.529 (omicron) variant became prevalent and two assessing data from adolescents 12 to 17 years of age before the emergence of the omicron variant (pre-omicron study) and after the omicron variant became prevalent. Associations were estimated with the use of Cox proportional-hazards regression models.

Results

Among children, the overall effectiveness of the 10-μg primary vaccine series against infection with the omicron variant was 25.7% (95% confidence interval [CI], 10.0 to 38.6). Effectiveness was highest (49.6%; 95% CI, 28.5 to 64.5) right after receipt of the second dose but waned rapidly thereafter and was negligible after 3 months. Effectiveness was 46.3% (95% CI, 21.5 to 63.3) among children 5 to 7 years of age and 16.6% (95% CI, −4.2 to 33.2) among those 8 to 11 years of age. Among adolescents, the overall effectiveness of the 30-μg primary vaccine series against infection with the omicron variant was 30.6% (95% CI, 26.9 to 34.1), but many adolescents had been vaccinated months earlier. Effectiveness waned over time since receipt of the second dose. Effectiveness was 35.6% (95% CI, 31.2 to 39.6) among adolescents 12 to 14 years of age and 20.9% (95% CI, 13.8 to 27.4) among those 15 to 17 years of age. In the pre-omicron study, the overall effectiveness of the 30-μg primary vaccine series against SARS-CoV-2 infection among adolescents was 87.6% (95% CI, 84.0 to 90.4) and waned relatively slowly after receipt of the second dose.

Conclusions

Vaccination in children was associated with modest, rapidly waning protection against omicron infection. Vaccination in adolescents was associated with stronger, more durable protection, perhaps because of the larger antigen dose. (Funded by Weill Cornell Medicine–Qatar and others.)

中文翻译：

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卡塔尔儿童和青少年的 Covid-19 疫苗保护

背景

针对 2019 年冠状病毒病（Covid-19）的 BNT162b2 疫苗已被授权用于 5 至 11 岁儿童和 12 至 17 岁青少年，但抗原剂量不同。

方法

我们评估了 BNT162b2 疫苗在卡塔尔儿童和青少年中对抗严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 感染的实际有效性。为了比较全国已接种疫苗的参与者队列中的 SARS-CoV-2 感染发病率与全国未接种疫苗的参与者队列中的发病率，我们进行了三项匹配的回顾性目标试验队列研究，其中一项评估数据来自儿童 5 B.1.1.529（omicron）变体流行后至 11 岁，以及 omicron 变体出现前（前 omicron 研究）和 omicron 变体流行后 12 至 17 岁青少年的两项评估数据。使用 Cox 比例风险回归模型估计关联性。

结果

在儿童中，10 μg 初级疫苗系列对抗 omicron 变体感染的总体有效性为 25.7%（95% 置信区间 [CI]，10.0 至 38.6）。服用第二剂后，有效性最高（49.6%；95% CI，28.5 至 64.5），但此后迅速下降，3 个月后可忽略不计。5至7岁儿童的有效率为46.3%（95% CI，21.5至63.3），8至11岁儿童的有效率为16.6%（95% CI，-4.2至33.2）。在青少年中，30 μg 初级疫苗系列对抗 omicron 变体感染的总体有效性为 30.6%（95% CI，26.9 至 34.1），但许多青少年在几个月前就已接种疫苗。自接受第二剂以来，有效性随着时间的推移而减弱。12至14岁青少年的有效率为35.6%（95% CI，31.2至39.6），15至17岁青少年的有效率为20.9%（95% CI，13.8至27.4）。在 pre-omicron 研究中，青少年中针对 SARS-CoV-2 感染的 30 μg 初级疫苗系列的总体有效性为 87.6%（95% CI，84.0 至 90.4），并且在接受第二剂后相对缓慢地下降。

结论

儿童接种疫苗对 omicron 感染的保护作用有限且迅速减弱。青少年接种疫苗可以提供更强、更持久的保护，这可能是因为抗原剂量更大。（由威尔康奈尔医学院卡塔尔等机构资助。）