Effectiveness of mRNA booster doses against the omicron variant

Abstract

Since its emergence in November, 2021, the omicron (B.1.1.529) variant of SARS-CoV-2 has rapidly spread and quickly overtaken the delta (B.1.617.2) variant as the most common cause of infection.1 Due to numerous spike mutations, the omicron variant showed increased transmissibility and reduced neutralisation by antibodies from prior infections compared with the wild-type virus and other variants of concern. Concurrently, breakthrough infections surged in populations with high vaccination rates, which expedited efforts to scale up booster vaccination.