Variant-Specific IgA Protects Against Omicron Infection

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 . NCT05142319.Conclusions We conclude that IgA may have a potential contributory role in protection against Omicron infection. Clinical Trials Registration . NCT05142319. Higher variant-specific IgA, but not IgG, antibody response at 1 month after booster vaccination was associated with infection risk, where individuals, who remained uninfected over the follow-up period of at least 8 months, had higher variant-specific IgA than individuals who became infected.