The adjusted vaccine effectiveness (VE) against moderate to severe COVID-19 infection in Taiwanese children aged 6 to 11 years was 69.9% for the Pfizer/BioNTech BNT162b2 vaccine and 75.5% for the Moderna mRNA-1273 vaccine during Omicron BA.2/BA.5 predominance in 2022, researchers from Chang Gung University estimated late last week in Biomedical Journal.
The adjusted VE against infection of any severity was 58.8% for BNT162b2 and 73.9% for mRNA-1273. Both vaccines maintained high protection in children with underlying medical conditions and reduced visits to the emergency department (ED).
The research was based on the Taiwan’s National Health Insurance Research Database and the National Immunization Information System on SARS-CoV-2–naive children 6 to 11 years old who either completed a two-dose primary series in May and June 2022 or were still unvaccinated through the end of 2022. Participants were followed from July to December 2022.
“In children, COVID-19 is usually less severe than in adults, however, infections remain common and can contribute to household and school-based transmission, and a small proportion of patients still develop severe disease requiring hospitalization or critical care, particularly those with underlying comorbidities,” the investigators noted.
Moderna vaccine tied to greater protection
Among 347,715 children, 33.2% received BNT162b2, 26.3% were given mRNA-1273, and 40.5% were unvaccinated. During follow-up, 32.0% of all participants contracted COVID-19. The crude infection rate was 39.7% in BNT162b2 recipients, 35.5% in the mRNA-1273 group, and 23.4% in unvaccinated children.
In total, 0.61% of participants developed moderate-to-severe COVID-19, including 0.29%, 0.23%, and 1.42% in the BNT162b2, mRNA-1273, and unvaccinated groups, respectively. Three deaths occurred, one in the BNT162b2 group and two in unvaccinated children, for corresponding death rates of 0.02% and 0.06%, respectively.
The crude incidence of infection was 0.35% in the BNT162b2 group, 0.21% in the mRNA-1273 group, and 0.79% in unvaccinated participants.
These findings support the continued use of pediatric COVID-19 vaccination, particularly in settings where prior infection remains relatively uncommon, and underscore the role of mRNA vaccines in preventing severe pediatric disease as SARS-CoV-2 continues to evolve.
Relative to no vaccination, the adjusted VE against ED-confirmed infection was 58.8% for BNT162b2 and 73.9% for mRNA-1273. VE against moderate-to-severe illness was 69.9% for BNT162b2 and 75.5% for mRNA-1273. Subgroup analyses showed consistent results, with generally higher effectiveness among children with underlying or catastrophic illness.
Likewise, in adjusted propensity-score–weighted analyses, both BNT162b2 and mRNA-1273 were linked to substantially lower risk of moderate-to-severe COVID-19 than their unvaccinated peers, corresponding to estimated VE of 69.9% and 75.5%, respectively. But because the study wasn’t designed to evaluate VE over time, the durability of protection wasn’t assessed.
Findings support continued vaccine use
The authors noted that the vaccines were effective despite being based on the ancestral SARS-CoV-2 spike protein and being used during an Omicron wave characterized by high transmissibility and immune evasion.
“These findings support the continued use of pediatric COVID-19 vaccination, particularly in settings where prior infection remains relatively uncommon, and underscore the role of mRNA vaccines in preventing severe pediatric disease as SARS-CoV-2 continues to evolve,” they concluded.
