Two doses of a COVID-19 mRNA vaccine were 40% effective against emergency department (ED) visits and hospitalization in preschool-aged children during a period of Omicron variant predominance, estimates a test-negative, case-control study using data from the New Vaccine Surveillance Network (NVSN).
Today in Morbidity and Mortality Weekly Report, a US Centers for Disease Control and Prevention (CDC)-led team published COVID-19 vaccine effectiveness (VE) estimates among 7,434 children aged 6 months to 4 years receiving ED care or being admitted to one of seven pediatric hospitals for acute respiratory infection (ARI) from July 2022 to September 2023. Data were obtained through chart abstraction and parent interviews.
"Vaccination coverage in this population remains markedly lower than that in the adult population, and complete primary series COVID-19 mRNA vaccination coverage in young children has been approximately 5% nationwide since January 2023," the researchers wrote. "As such, vaccine effectiveness (VE) estimates in infants and children aged 6 months–4 years are limited."
Uptake varied by region, race
Of all participants, 86% were unvaccinated, 4% had received one dose of any COVID-19 vaccine, and 10% had received at least two doses. The median interval since receipt of the last vaccine dose was 93 days.
Uptake of two or more doses was about two to six times higher in Seattle than at other NVSN sites, consistent with high vaccination coverage in this area for routine childhood vaccines.
Despite low vaccination coverage and the circulation of several Omicron subvariants, COVID-19–associated ED visits and hospitalization among children with ARI enrolled in NVSN were rare.
Compared with their White peers, Black children were roughly seven times less likely—and Hispanic children were about three times less likely—to have received at least two vaccine doses, which the study authors said highlights the continued need to promote access and reduce vaccine hesitancy.
Of the 7,434 children, 5% tested positive for COVID-19. Compared with no vaccination, receipt of two or more COVID-19 mRNA vaccine doses had an estimated effectiveness of 40% (95% confidence interval [CI], 8% to 60%) against ED visits and hospitalization. VE of one dose was 31%, although the 95% CI dipped below zero (-27% to 62%).
Results support vaccination for kids
"Despite low vaccination coverage and the circulation of several Omicron subvariants, COVID-19–associated ED visits and hospitalization among children with ARI enrolled in NVSN were rare, suggesting most children in this age group experience mild illness from these subvariants or have immune protection from previous SARS-CoV-2 exposure," the study authors wrote.
The results, they said, suggest that COVID-19 mRNA vaccines offer protection against ED visits and hospitalization and are consistent with other VE estimates for children younger than 5 years, which range from 29% for two doses of the Moderna vaccine to 43% for three doses of the Pfizer/BioNTech vaccine.
"The findings in this report support the recommendation for COVID-19 vaccination for all children aged ≥6 months and highlight the importance of completion of a primary series for young children," they wrote. "However, low vaccination coverage and low incidence of medically attended COVID-19 limit precision in these VE estimates."