Department of Paediatrics and Adolescent Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark; Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Department of Paediatrics and Adolescent Medicine, Aarhus University Hospital, Aarhus N, Denmark.
Lancet Child Adolesc Health. 2022 Jul;6(7):459-465. doi: 10.1016/S2352-4642(22)00100-6. Epub 2022 May 6.
Multisystem inflammatory syndrome in children (MIS-C) occurs after infection with SARS-CoV-2 and its incidence is likely to depend on multiple factors, including the variant of the preceding SARS-CoV-2 infection and vaccine effectiveness. We aimed to estimate the incidence of MIS-C, and describe the clinical phenotype, following the delta variant of SARS-CoV-2 (B.1.617.2 and sublineages) according to vaccination status. We aimed to compare the incidence and clinical phenotype of MIS-C from our cohort during the pre-delta era.
This prospective, population-based cohort study included patients aged 0-17 years hospitalised with MIS-C in Denmark, according to the US Centers for Disease Control and Prevention case definition, from Aug 1, 2021, to Feb 1, 2022, a period dominated by the delta variant. We identified MIS-C cases via a nationwide research collaboration involving real-time data collection from all 18 paediatric departments. Aggregated number of SARS-CoV-2 infections by vaccination status was obtained from the Danish COVID-19 surveillance registries. The incidence of MIS-C was calculated using the estimated number of infected individuals by vaccination status. We calculated the incidence of MIS-C per 1 000 000 vaccinated and unvaccinated person-years, and estimated vaccine effectiveness as 1-incidence rate ratio using Poisson regression. Incidence and phenotype of MIS-C were compared with MIS-C cases from the first year of the pandemic. This study is registered at ClinicalTrials.gov, NCT05186597.
We identified 51 MIS-C cases among unvaccinated individuals and one in a fully vaccinated adolescent. The incidence of MIS-C was one in 3400 unvaccinated individuals (95% CI 2600-4600) with the delta variant and one in 9900 vaccinated individuals (95% CI 1800-390 000) with breakthrough infection. The estimated vaccine effectiveness against MIS-C after the delta variant was 94% (95% CI 55-99; p=0·0061) in individuals aged 5-17 years. The clinical phenotype during the delta wave was comparable to the pre-delta era.
We found the incidence and phenotype of MIS-C in unvaccinated children during the delta wave to be similar to the incidence during the first year of the pandemic. We found vaccine effectiveness to be high against MIS-C, which we suggest was due to protection from infection and, possibly, a decreased incidence of MIS-C after breakthrough infection. Knowledge of the incidence of MIS-C after different SARS-CoV-2 variants and the effect of vaccination might contribute to the elucidation of the extent to which MIS-C is a vaccine-preventable disease.
National Ministry of Higher Education and Science and Innovation Fund Denmark.
儿童多系统炎症综合征（MIS-C）发生在感染 SARS-CoV-2 之后，其发病率可能取决于多种因素，包括先前 SARS-CoV-2 感染的变异株和疫苗有效性。我们旨在根据 delta 变异株（B.1.617.2 及其亚系）的疫苗接种情况，估计 MIS-C 的发病率，并描述其临床表型。我们旨在比较 delta 前时代我们队列中 MIS-C 的发病率和临床表型。
这是一项前瞻性、基于人群的队列研究，纳入了 2021 年 8 月 1 日至 2022 年 2 月 1 日期间丹麦因符合美国疾病控制与预防中心定义的 MIS-C 而住院的 0-17 岁儿童，该时期以 delta 变异株为主。我们通过一项全国性的研究合作，从所有 18 个儿科部门实时收集数据，确定了 MIS-C 病例。根据丹麦 COVID-19 监测登记处，获得了按疫苗接种状态汇总的 SARS-CoV-2 感染人数。使用按疫苗接种状态估计的感染人数计算 MIS-C 的发病率。我们计算了每 100 万接种和未接种人年的 MIS-C 发病率，并使用泊松回归估计疫苗有效性为 1-发病率比。将 MIS-C 的发病率和表型与大流行第一年的 MIS-C 病例进行比较。本研究在 ClinicalTrials.gov 注册，NCT05186597。
我们在未接种人群中发现了 51 例 MIS-C 病例，在一名完全接种疫苗的青少年中发现了 1 例。delta 变异株时，MIS-C 的发病率为每 3400 名未接种人群 1 例（95%CI 2600-4600），突破性感染时每 9900 名接种人群 1 例（95%CI 1800-390000）。在 5-17 岁人群中，delta 变异株后疫苗对 MIS-C 的估计有效性为 94%（95%CI 55-99；p=0.0061）。delta 波期间的临床表型与 delta 前时期相似。
我们发现 delta 波期间未接种儿童的 MIS-C 发病率和表型与大流行第一年的发病率相似。我们发现疫苗对 MIS-C 非常有效，这表明疫苗接种可以预防感染，并且可能降低突破性感染后的 MIS-C 发病率。了解不同 SARS-CoV-2 变异株后的 MIS-C 发病率和疫苗接种的效果，可能有助于阐明 MIS-C 在多大程度上是一种可通过疫苗预防的疾病。
国家高等教育和科学创新基金丹麦。
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