Background: The emergence of rapidly evolving 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 two 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 post booster vaccination, compared with individuals who became infected.
Conclusions: We conclude that IgA may have a potential contributory role in protection against Omicron infection.
Keywords: COVID-19; IgA; Omicron; S protein; SARS-CoV-2; antibodies; mRNA vaccine.
© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.