LONDON, Jul 21 (Reuters) – Two doses of the vaccines from Pfizer or AstraZeneca are almost as effective against the Delta variant of the coronavirus as against the Alpha mutation, the world’s former dominant strain, a study published on Wednesday indicated.
Authorities say the vaccines are highly effective against Delta, currently the world’s dominant variant, although the UK study reiterated that one injection of the vaccines is not enough to obtain high protection.
The study, published in the New England Journal of Medicine, confirms preliminary findings revealed by the Public Health Service of England (PHE) in May on the efficacy of vaccines manufactured by Pfizer-BioNTech and the University of Oxford-AstraZeneca, based on in field data.
The study found that two doses of the Pfizer injection were 88% effective in preventing symptomatic disease from the Delta variant, compared to 93.7% against the Alpha variant, generally the same as previously reported.
Two injections of the AstraZeneca vaccine were 67% effective against the Delta variant, versus 60% originally reported, and 74.5% effective against the Alpha variant, compared to an original estimate of 66% effectiveness.
“Only modest differences in vaccine effectiveness were seen with the Delta variant compared to the Alpha variant after receiving two doses of the vaccine,” the PHE researchers wrote in the study.
Data from Israel have estimated a lower effectiveness of Pfizer injection against symptomatic disease, although protection against severe cases remains high.
The PHE had previously said that a first dose of either vaccine was about 33% effective against symptomatic Delta variant disease.
The full study published Wednesday found that one dose of the Pfizer injection was 36% effective and one injection of the AstraZeneca vaccine was about 30% effective.