Two vaccine doses of Pfizer or AstraZeneca are nearly as effective against the highly transmissible Covid-19 Delta variant as they are against the previously dominant Alpha strain, a fresh study shows.
The report published in the New England Journal of Medicine says the vaccines were highly effective against the Delta variant, which is now the dominant strain globally, provided that one gets two jabs.
The study adds weight to findings by Public Health England (PHE) in May about the efficacy of COVID-19 shots made by vaccine makers Pfizer-BioNTech and Oxford-AstraZeneca based on field data.
The survey shows that Pfizer was 88 per cent effective at preventing symptomatic disease from the Delta variant with both doses, compared with 93.7 per cent against the Alpha variant, essentially the same as previously reported.
Two shots of AstraZeneca vaccine were 67 per cent effective against the Delta variant, up from 60 per cent from earlier studies and 74.5 per cent effective against the Alpha variant, compared with an original 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,” Public Health England researchers noted.
Data from Israel, however, shows that Pfizer’s shot is less effective against symptomatic disease, although protection against severe infection remains high.
The full study published on Wednesday found that one dose of Pfizer’s shot was 36 per cent effective while a shot of AstraZeneca was about 30 per cent effective.
“Our finding of reduced effectiveness after the first dose would support efforts to maximize vaccine uptake with two doses among vulnerable groups in the context of circulation of the Delta variant,” the study said in part.
Recently, researchers from Beth Israel Deaconess Medical Center in the US city of Boston also said that in a laboratory setting, the antibody response from the one-dose Johnson & Johnson vaccine worked well against Delta and that immune response lasted for about eight months.
In June, makers of Russia’s Sputnik vaccine also said that it was about 90 per cent effective against Delta variant.
The vaccine, which Russia has actively marketed globally, was previously found by researchers to be almost 92 per cent effective against the original strain, however, it has raised some controversy as it was introduced to the public even before a full trial was done and it is yet to get greenlight from the World Health Organization.