Study Finds Modest Seasonal Variation in Children's Antibody Responses to Vaccines, But No Clear Link to Protection

A study of nearly 48,000 children found measurable seasonal differences in how strongly their immune systems responded to vaccines against 14 infections, including measles, polio and chickenpox. Laura Barrero Guevara at New York University and colleagues pooled results from 96 randomised-controlled trials conducted across multiple countries and times of year.

They measured immunogenicity, the strength of the antibody response triggered by vaccination, after excluding children who already carried antibodies to the target pathogens.

In temperate regions of both hemispheres, antibody responses were stronger during winter months. Closer to the equator, responses still showed annual fluctuations, but the timing of peak responses varied by vaccine, with larger swings observed for rotavirus and polio.

The initial hypothesis was that seasonal patterns would represent an extension of circadian rhythms driven by changes in day length.

That model predicted smaller seasonal swings near the equator, where day length varies less. The data did not match that prediction. Matthieu Domenech de Cellès at the Max Planck Institute for Infection Biology in Berlin, a member of the research team, said other mechanisms or a combination of photoperiodism and additional factors may be involved.

Cathy Wyse at the University of Edinburgh, who was not part of the study, said the broader implication is that human immune function differs across seasons. She cited her own 2020 work that documented seasonal changes in inflammatory markers and several immune-cell types.

Manuel Irimia at the Centre for Genomic Regulation in Barcelona and colleagues previously identified seasonal shifts in gene expression in multiple tissues, including hormone-producing regions of the brain and testes and many immune-related genes.