Incidence and clinical phenotype of multisystem inflammatory syndrome in children after infection with the SARS-CoV-2 delta variant by vaccination status: a Danish nationwide prospective cohort study.
Lancet Child Adolesc Health
; 6(7): 459-465, 2022 07.
Article
in English
| MEDLINE | ID: covidwho-2132839
ABSTRACT
BACKGROUND:
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.METHODS:
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.FINDINGS:
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.INTERPRETATION:
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.FUNDING:
National Ministry of Higher Education and Science and Innovation Fund Denmark.
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
Systemic Inflammatory Response Syndrome
/
SARS-CoV-2
/
COVID-19
Type of study:
Cohort study
/
Observational study
/
Prognostic study
Topics:
Long Covid
/
Vaccines
/
Variants
Limits:
Adolescent
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Child
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Child, preschool
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Humans
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Infant
/
Infant, Newborn
Country/Region as subject:
Europa
Language:
English
Journal:
Lancet Child Adolesc Health
Year:
2022
Document Type:
Article
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