Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy.
Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy.
Lancet. 2022 Jul 9;400(10346):97-103. doi: 10.1016/S0140-6736(22)01185-0. Epub 2022 Jul 1.
By April 13, 2022, more than 4 months after the approval of BNT162b2 (Pfizer-BioNTech) for children, less than 40% of 5-11-year-olds in Italy had been vaccinated against COVID-19. Estimating how effective vaccination is in 5-11-year-olds in the current epidemiological context dominated by the omicron variant (B.1.1.529) is important to inform public health bodies in defining vaccination policies and strategies.
In this retrospective population analysis, we assessed vaccine effectiveness against SARS-CoV-2 infection and severe COVID-19, defined as an infection leading to hospitalisation or death, by linking the national COVID-19 surveillance system and the national vaccination registry. All Italian children aged 5-11 years without a previous diagnosis of infection were eligible for inclusion and were followed up from Jan 17 to April 13, 2022. All children with inconsistent vaccination data, diagnosed with SARS-CoV-2 infection before the start date of the study or without information on the municipality of residence were excluded from the analysis. With unvaccinated children as the reference group, we estimated vaccine effectiveness in those who were partly vaccinated (one dose) and those who were fully vaccinated (two doses).
By April 13, 2022, 1 063 035 (35·8%) of the 2 965 918 children aged 5-11 years included in the study had received two doses of the vaccine, 134 386 (4·5%) children had received one dose only, and 1 768 497 (59·6%) were unvaccinated. During the study period, 766 756 cases of SARS-CoV-2 infection and 644 cases of severe COVID-19 (627 hospitalisations, 15 admissions to intensive care units, and two deaths) were notified. Overall, vaccine effectiveness in the fully vaccinated group was 29·4% (95% CI 28·5-30·2) against SARS-CoV-2 infection and 41·1% (22·2-55·4) against severe COVID-19, whereas vaccine effectiveness in the partly vaccinated group was 27·4% (26·4-28·4) against SARS-CoV-2 infection and 38·1% (20·9-51·5) against severe COVID-19. Vaccine effectiveness against infection peaked at 38·7% (37·7-39·7) at 0-14 days after full vaccination and decreased to 21·2% (19·7-22·7) at 43-84 days after full vaccination.
Vaccination against COVID-19 in children aged 5-11 years in Italy showed a lower effectiveness in preventing SARS-CoV-2 infection and severe COVID-19 than in individuals aged 12 years and older. Effectiveness against infection appears to decrease after completion of the current primary vaccination cycle.
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For the Italian translation of the summary see Supplementary Materials section.
截至 2022 年 4 月 13 日，辉瑞-生物技术公司（Pfizer-BioNTech）批准为 5-11 岁儿童接种疫苗 4 个多月后，意大利不到 40%的该年龄段儿童接种了 COVID-19 疫苗。在当前由奥密克戎变异株（B.1.1.529）主导的流行病学环境下，评估疫苗在 5-11 岁儿童中的有效性对于告知公共卫生机构制定疫苗接种政策和策略非常重要。
在这项回顾性人群分析中，我们通过将国家 COVID-19 监测系统和国家疫苗接种登记处相联系，评估了针对 SARS-CoV-2 感染和严重 COVID-19（定义为导致住院或死亡的感染）的疫苗有效性。所有无先前感染史的 5-11 岁意大利儿童均有资格入组，并从 2022 年 1 月 17 日至 4 月 13 日进行随访。所有疫苗接种数据不一致、在研究开始前被诊断为 SARS-CoV-2 感染或无居住地信息的儿童均被排除在分析之外。以未接种疫苗的儿童为参照组，我们评估了部分接种（一剂）和完全接种（两剂）儿童的疫苗有效性。
截至 2022 年 4 月 13 日，在纳入研究的 2965918 名 5-11 岁儿童中，1063035 名（35.8%）已接种两剂疫苗，134386 名（4.5%）儿童仅接种了一剂，1768497 名（59.6%）未接种疫苗。在研究期间，共报告了 766756 例 SARS-CoV-2 感染病例和 644 例严重 COVID-19 病例（627 例住院，15 例进入重症监护病房，2 例死亡）。总体而言，完全接种组针对 SARS-CoV-2 感染的疫苗有效性为 29.4%（95%CI 28.5-30.2），针对严重 COVID-19 的疫苗有效性为 41.1%（22.2-55.4），部分接种组针对 SARS-CoV-2 感染的疫苗有效性为 27.4%（26.4-28.4），针对严重 COVID-19 的疫苗有效性为 38.1%（20.9-51.5）。疫苗接种后 0-14 天，完全接种组针对感染的疫苗有效性达到峰值 38.7%（37.7-39.7），而在完全接种后 43-84 天，疫苗有效性降至 21.2%（19.7-22.7）。
意大利 5-11 岁儿童接种 COVID-19 疫苗在预防 SARS-CoV-2 感染和严重 COVID-19 方面的效果低于 12 岁及以上人群。接种后感染的有效性似乎会随着当前初级疫苗接种周期的完成而下降。
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