Vaccine Effectiveness against SARS-CoV-2 among Household Contacts during Omicron BA.2–Dominant Period, Japan

Abstract

We calculated attack rates for household contacts of COVID-19 patients during the SARS-CoV-2 Omicron BA.2–dominant period in Japan. Attack rates among household contacts without recent (<3 months) vaccination was lower for contacts of index patients with complete vaccination than for contacts of index patients without complete vaccination, demonstrating indirect vaccine effectiveness.

Keywords

• COVID-19
• Contact tracing
• COVID-19 vaccines
• respiratory diseases
• incidence
• risk factors