In this multicenter, prospective, test-negative, case-control study in Japan, the effectiveness of both BA.1-containing and BA.4/BA.5-containing bivalent coronavirus disease 2019 mRNA vaccines against symptomatic infection during the BA.5-dominant period was high compared with no vaccination (65% and 76%) and moderate compared with monovalent vaccines administered over half a year earlier (46% combined).
Keywords: COVID-19; SARS-CoV-2; SARS-CoV-2 variants; test-negative design; vaccine effectiveness.
© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.