Two doses of Pfizer, AstraZeneca shots effective against Delta variant, study finds Two doses of Pfizer or AstraZeneca's COVID-19 vaccine are nearly as effective against the highly transmissible Delta coronavirus variant as they are against the previously dominant Alpha variant, a study published on Wednesday showed. Reuters Staff U.S.

The study, published in the New England Journal of Medicine, confirms headline findings given by Public Health England in May about the efficacy of COVID-19 vaccines made by Pfizer-BioNTech and Oxford-AstraZeneca, based on real-world data.