Effect of COVID-19 vaccination on household transmission of SARS-CoV-2 in the Omicron era: The Vaccine Effectiveness, Networking, and Universal Safety (VENUS) study

Abstract

ObjectivesTo evaluate the effectiveness of vaccination on reducing household transmission of SARS-CoV-2 among common household types in Japan during the Omicron variant wave. MethodsThis retrospective study was conducted using vaccination records, COVID-19 infection data, and resident registry data from two Japanese municipalities. Households that experienced their first COVID-19 case between January and April 2022 were categorized into two groups according to the presence/absence of children aged ≤11 years. We constructed multivariable logistic regression models with generalized estimating equations to calculate the odds ratios (ORs) and 95% confidence intervals for household transmission according to the vaccination statuses of primary cases and household contacts. ResultsWe analyzed 7326 households with 17,586 contacts. In all households, the OR for household transmission was <0.6 (P <0.001) when the primary case and/or contact were vaccinated. In households with children aged ≤11 years, the OR was 0.71 (P <0.001) when only the contact was vaccinated. In households with all members aged ≥12 years, the OR was <0.5 (P <0.001) when the primary case and/or contact were vaccinated. ConclusionCOVID-19 vaccination effectively reduced household transmission in Japan during the Omicron variant wave.