mRNA vaccine in children aged 5 to 11 years is associated with fewer symptomatic COVID-19 infections and less multisystem inflammatory syndrome

Reference

Watanabe A, Kani R, Iwagami M, Takagi H, Yasuhara J, Kuno T. Assessment of efficacy and safety of mRNA COVID-19 vaccines in children aged 5 to 11 years: a systematic review and meta-analysis. JAMA Pediatr 2023;177(4):384-394.

Synopsis

These authors searched PubMed and Embase, plus the reference lists of retrieved studies, to identify peer-reviewed studies that evaluated the effectiveness and safety of 2-dose mRNA vaccines against COVID-19 in children 5 to 11 years of age. They included 17 studies: 2 randomized trials, 12 cohort studies, and 3 case-control studies. In aggregate, the studies included 10,935,541 vaccinated children and 2,635,251 unvaccinated children. The median follow-up in the studies ranged from 7 days to 90 days. Overall, the randomized trials were at low risk of bias, and the others were generally at low risk of bias with the exception of the potential for confounding. The pooled data from the 2 randomized trials and 11 of the observational studies show that vaccinated children were less likely than unvaccinated children to have infections with or without symptoms (odds ratio [OR] 0.47; 95% CI 0.35 - 0.64), to have symptomatic infections (OR 0.53; 0.41 - 0.79), to be hospitalized (OR 0.32; 0.15 - 0.68), or to develop multisystem inflammatory syndrome (OR 0.05; 0.02 - 0.10; this is the lowest OR I recall ever seeing!). The authors detected marked variability for all these outcomes, except multisystem inflammatory syndrome. Adverse event data came from the 2 randomized trials plus 5 observational studies. Nearly all vaccinated children experienced at least one local adverse reaction following the first injection and after the second injection (86.3% for each; marked heterogeneity). However, the rate of having at least one systemic reaction was 45.1% after the first dose and 56.4% after the second dose. These systemic reactions were mainly in the form of fatigue (25% - 33%) and headache (16% - 25%). The rates of adverse reactions that prevented normal daily activities were 4.9% and 8.8% after the first and second doses, respectively. Myocarditis following the first and second dose occurred in 1.3 per million and 1.8 per million, respectively.