Antigenic drift in SARS-CoV-2: diminished vaccine protection in pediatric populations against Omicron and its JN.1 subvariant.

BACKGROUND

The COVID-19 vaccination campaign for children in Brazil evolved gradually from 2021 to the present, adapting to regulatory framework from the Brazilian Health Regulatory Agency (ANVISA). However, while adults received updated vaccines targeting newer variants, children and adolescents continued to receive vaccines based on the original wild-type strain.

RESEARCH DESIGN AND

METHODS

This study evaluates the vaccine-induced protective immunity, measured by serum antibody and neutralization responses, in vaccinated (n = 61) and unvaccinated (n = 13) pediatric populations against the wild-type (WT), Omicron BA.1, and JN.1 SARS-CoV-2 variants.

RESULTS

Vaccinated children exhibited significantly higher antibody levels and neutralization titers against WT compared to unvaccinated peers (p ≤ 0.0001). However, responses to BA.1 were drastically reduced, and JN.1 subvariant neutralization was limited in both groups. Immunoinformatic analysis revealed a marked decline in conserved neutralizing antibody-targeting epitopes within the Spike protein: from 465 in WT to 49 in BA.1 and 41 in JN.1. This substantial antigenic drift underscores the immunological gap created by vaccinating children with outdated formulations.

CONCLUSIONS

Our findings highlight the urgent need for updating pediatric vaccines to include antigens from circulating virus variants in order to increase immune protection and reduce susceptibility to infection and controlling community transmission.