Pfizer found to be 88 per cent effective at preventing symptomatic disease from delta variant.

Two doses of Pfizer-BioNTech or AstraZeneca-Oxford’s COVID-19 vaccines are nearly as effective against the highly transmissible delta coronavirus variant as they are against the previously dominant alpha variant, a new study shows.

Officials say 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 on Wednesday, confirms headline findings given by Public Health England (PHE) in May about the efficacy of COVID-19 vaccines made by Pfizer-BioNTech and Oxford-AstraZeneca, based on real-world data.

The research team found that two doses of Pfizer’s shot was 88 per cent effective at preventing symptomatic disease from the delta variant, compared to 93.7 per cent effective against the alpha variant, broadly the same as previously reported.

Two shots of the AstraZeneca vaccine were 67 per cent effective against the delta variant, up from 60 per cent originally reported, and 74.5 per cent effective against the alpha variant, compared to an original estimate of 66 per cent effectiveness.

“Only modest differences in vaccine effectiveness were noted with the delta variant as compared with the Alpha variant after the receipt of two vaccine doses,” PHE researchers wrote in the study.

The research didn’t look at the effectiveness of mixing brands for different doses, though ongoing U.K. research has shown the Pfizer-BioNTech and AstraZeneca-Oxford vaccines appear to generate a stronger immune response than having two rounds of the AstraZeneca shot.