Two doses of Pfizer or AstraZeneca are effective against Delta variant, study finds

The study confirms the preliminary results revealed in May by the Public Health Service of England (PHE) on the efficacy of vaccines manufactured by Pfizer-BioNTech and the University of Oxford-AstraZeneca, based on field data.

figure 1.webp

Vaccine efficacy against Alpha and Delta variants, depending on dose and type of vaccine.

New England Journal of Medicine

The study further found that two doses of the Pfizer injection had an effect 88% effective to prevent symptomatic Delta variant disease, compared to 93.7% against the Alpha variant, the same as previously reported.

Two injections of the AstraZeneca vaccine were 67% effective against the Delta variant, compared to 60% initially reported, and a 74.5% effective against the Alpha variant, compared to an original estimate of 66% effectiveness.

“Only modest differences in vaccine efficacy were seen with the Delta variant compared to the Alpha variant after receiving two doses of the vaccine”, PHE researchers wrote in the study.

2.jpeg table

Vaccine efficacy against alpha variant or negative target status S and the delta variant or positive state of the target S , depending on the dose and type of vaccine.

New England Journal of Medicine

Data Israel found the Pfizer injection to be less effective against symptomatic illnesses, although protection against severe cases remains high.

The PHE had previously stated that a first dose of either vaccine was about 33% effective against symptomatic Delta variant disease.

The full study released on Wednesday found that one dose of Pfizer vaccine was 36% effective and one injection of AstraZeneca vaccine was approximately 30% effective.

“Our finding of reduced efficacy after the first dose would support efforts to maximize uptake of the two-dose vaccine among vulnerable groups in the context of the Delta variant circulation,” said the study authors.