Variant-Specific IgA Protects Against Omicron Infection

Abstract

Background: The emergence of rapidly evolving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, coupled with waning vaccine-induced immunity, has contributed to the rise of vaccine breakthrough infections. It is crucial to understand how vaccine-induced protection is mediated. Methods: We examined 2 prospective cohorts of mRNA vaccinated and boosted individuals during the Omicron wave of infection in Singapore. Results: We found that individuals who remain uninfected over the follow-up period had a higher variant-specific IgA, but not IgG, antibody response at 1 month after booster vaccination, compared with individuals who became infected. Conclusions: We conclude that IgA may have a potential contributory role in protection against Omicron infection. Clinical Trials Registration.