Effectiveness of Covid-19 vaccines against the B.1.617.2 (delta) variant
New England Journal of Medicine — Bernal JL, Andrews N, Gower C, et al. | July 26, 2021
Researchers examined the effectiveness of the BNT162b2 and ChAdOx1 nCoV-19 vaccines against the B.1.617.2 (delta) variant of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has contributed to a surge in cases in India and has now been identified across the globe. They used a test-negative case–control design herein. Findings revealed a notably lower effectiveness after one dose of vaccine (BNT162b2 or ChAdOx1 nCoV-19) among persons with the delta variant compared with those with the alpha variant; similar results were recorded for both vaccines. Overall, there were only modest differences in vaccine effectiveness with the delta variant as compared with the alpha variant after the receipt of two vaccine doses. In vaccine effectiveness, more marked absolute differences were observed after the receipt of the first dose. In view of this finding, they emphasize making efforts to enhance vaccine uptake with two doses among vulnerable populations.