Impact of vaccination on new SARS-CoV-2 infections in the UK
Pritchard E., Matthews P., Stoesser N., Eyre D., Gethings O., Vihta K-D., Jones J., House T., VanSteenHouse H., Bell I., Bell J., Newton J., Farrar J., Diamond I., Rourke E., Studley R., Crook D., Peto T., Walker S., Pouwels K.
The effectiveness of COVID-19 vaccination in preventing new SARS-CoV-2 infections in the general community is still unclear. Here, we used the Office for National Statistics (ONS) COVID-19 Infection Survey, a large community-based survey of individuals living in randomly selected private households across the UK, to assess the effectiveness of BNT162b2 (Pfizer-BioNTech) and ChAdOx1 nCoV-19 (Oxford-AstraZeneca; ChAdOx1) vaccines against any new SARS-CoV-2 PCR-positive tests, split according to self-reported symptoms, cycle threshold value (<30 versus ≥30) as a surrogate for viral load, and gene positivity pattern (compatible with B.1.1.7 or not). Using 1,945,071 RT-PCR results from nose and throat swabs taken from 383,812 participants between 1 December 2020 and 8 May 2021, we found that vaccination with the ChAdOx1 or BNT162b2 vaccines already reduced SARS-CoV-2 infections ≥21 days after the first dose (61%, 95% CI 54 to 68% versus 66%, 95% CI 60 to 71%, respectively) with greater reductions observed after a second dose (79%, 95% CI 65 to 88% versus 80%, 95% CI 73 to 85%, respectively). Largest reductions were observed for symptomatic infections and/or infections with a higher viral burden. Overall, COVID-19 vaccination reduced the number of new SARS-CoV-2 infections, with the largest benefit received after two vaccinations and against symptomatic and high viral burden infections, and with no evidence of difference between the BNT162b2 and ChAdOx1 vaccines.