Assessment of 10 Million Vaccinated Children Affirms mRNA COVID-19 Vaccines Safe, Effective

A meta-analysis of studies assessing over 10 million children vaccinated against COVID-19 affirmed that the mRNA vaccines reduced risk for both symptomatic and asymptomatic infection, severe illness requiring hospitalization, the complication of multisystem inflammatory syndrome in children (MIS-C), and with lower risk for myocarditis than is associated with the infection.

“Our findings can help inform physicians and other clinicians, parents, and policy makers about the effectiveness and safety of COVID-19 vaccination for children aged 5 to 11 years,” stated Atsuyuki Watanabe, MD, Division of Hospital Medicine, University of Tsukuba Hospital, Tsukuba, Ibaraki, Japan, and colleagues.

In an accompanying editorial, Paul Offit, MD, Vaccine Education Center, Children’s Hospital of Philadelphia, Philadelphia, PA, emphasized the importance of the findings and scope of the study for parents who are not only concerned about vaccine safety, but may perceive COVID-19 as not severe enough in young children to warrant prevention.

“While it is true that COVID-19 is far less devastating in children than older adults, children are still at risk of serious and rarely fatal infections,” Offit pointed out.

“Parents should be both compelled and reassured,” suggests Offit, by the potential consequences of the virus continuing to circulate, and the relative safety of the effective vaccines that pose only “miniscule” risk of myocarditis in young children.

“Given the amount of information currently available to parents, the decision to vaccinate their children should be an easy one,” Offit asserts.

Watanabe and colleagues identified 15 observational studies and 2 randomized clinical trials involving 10,935,541 vaccinated children age 5 to 11 years (median or mean age 8-9.5 years) and 2,635,251 unvaccinated (7.0-9.5 years). Studies were distinguished between those initiated after November 2021 during omicron spread, and prior studies coinciding with delta subvariant prominence.

The primary outcome was SARS-CoV-2 infection with or without symptoms. Secondary outcomes included hospitalization from severe infection or complications such as MIS-C, as well as any adverse events, and distinguishing those that interfered with normal daily activity.

Watanabe and colleagues reported that the 2-dose mRNA COVID-19 vaccination, compared to no vaccination, was associated with lower risks of SARS-CoV-2 infection with or without symptoms (odds ratio [OR], 0.47, at 95% confidence interval [CI] 0.35-0.64); symptomatic infection (OR 0.53, 0.41-0.70) hospitalizations (OR 0.32, 0.15-0.68) and MIS-C (OR 0.05, 0.02-0.10). While the vaccines were effective in both time periods, the protection was more pronounced against the delta subvariant than omicron.

The prognosis of MIS-C occurring from the SARS-CoV-2 infection, the investigators indicated, “was likely to be much poorer” than that occurring with vaccination. Offit remarked on this, indicating “fortunately, myocarditis following vaccination is generally short-lived and self-resolving.”

Local irritation at the site of injection was experienced by most vaccinated children. Adverse events that prevented normal daily activities were reported by 8.8% (5.4-14.2%); with most ranging from 1 to 2 days, while local pain and redness could last for 3 days or longer. One prospective cohort study found that 4 of 449 children (0.8%) has symptoms including headache and lymphadenopathy which lasted for 7 days after the second injection.

“While vaccination, compared with placebo, was associated with higher incidences of adverse events, the overall frequency of severe adverse events, including myocarditis was low,” Watanabe and colleagues point out.

“These data support the safety and efficacy of mRNA COVID-19 vaccines among children aged 5 to 11 years and endorse the universal age-based recommendations,” they conclude.