The effect of vaccination on transmission of SARS-CoV-2 (COVID-19): a rapid review

Abstract

This is an update (literature search up to 15 March 2022) of a rapid review examining whether vaccination against SARS-CoV-2 (COVID-19) affects transmission of SARS-CoV-2. Streamlined systematic methodologies were used to accelerate the review process. The update identified 17 additional studies: 6 studies reported on transmission and 11 studies reported viral load. There was high heterogeneity across studies, which varied in design, participant characteristics and SARS-CoV-2 variants reported. Evidence from this update supports previous findings that that transmission of Omicron and Delta variants is lowest in booster-vaccinated people, followed by fully vaccinated people, with the highest rate of transmission in unvaccinated people. Additionally, some studies compared transmission between different variants or sub-variants; risk of transmission appears to be higher with Omicron than Delta, regardless of vaccination status.