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.

Officials said vaccines are highly effective against the Delta variant, now the dominant variant worldwide, though the study reiterated that one shot of the vaccines is not enough for high protection.

The study, published in the New England Journal of Medicine, confirms headline findings given by Public Health England (PHE) in May about the efficacy...