Two Pfizer, AstraZeneca doses work against Delta variant: study

Two doses of Pfizer are 88 percent effective in preventing the delta variant while two doses of AstraZeneca are 67 percent effective.

Two doses of the COVID-19 vaccine from Pfizer or AstraZeneca are almost as effective against the highly permeable delta coronavirus variant as they are against the previously dominant alpha version, according to a new study.

Research published Wednesday in the New England Journal of Medicine showed the vaccines were highly effective against the delta variant, which is now the dominant strain worldwide, provided a person received two shots.

The study confirms key findings made by Public Health England (PHE) in May about the efficacy of COVID-19 vaccines based on real-world data by Pfizer-BioNtech and Oxford-AstraZeneca.

Wednesday’s study found that Pfizer was 88 percent more effective at preventing symptomatic disease than the delta version with both doses, compared with 93.7 percent against the alpha version, roughly the same as previously reported.

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

“Only a slight difference in vaccine effectiveness was noted with the delta version after receiving two vaccine doses compared with the alpha version,” the researchers from Public Health England wrote.

Data from Israel has led to speculation that Pfizer’s shot is less effective against symptomatic disease, although protection against severe disease remains high.

PHE previously said that the first dose of any vaccine was about 33 percent effective against symptomatic disease from the delta variant.

Other Vaccines Also Useful

The full study, published Wednesday, found that a single dose of Pfizer’s shot was 36 percent effective and a single dose of AstraZeneca’s vaccine was about 30 percent effective.

“Our finding of reduced effectiveness after the first dose will support efforts to maximize the vaccine with two doses among vulnerable groups in terms of circulation of the delta variant,” the study authors said.

In June, the makers of Russia’s Sputnik vaccine also said it was about 90 percent effective against the highly infectious Delta variant. [File: Leonardo Fernandez Viloria/Reuters]

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 a single-dose Johnson & Johnson vaccine worked well against Delta and this immune response lasted for about eight months.

In June, the makers of Russia’s Sputnik vaccine also said it was about 90 percent effective against the highly infectious Delta variant.

The shot, which Russia has actively marketed overseas, was previously found by researchers to be about 92 percent effective against the original strain of coronavirus.

Denis Logunov, deputy director of Moscow’s Gamalya Institute, which developed Sputnik, said the delta variant efficacy figure was calculated based on digital medical and vaccine records, Russian state-owned RIA news agency reported.

However, the Sputnik vaccine has sparked some controversy as it was introduced to the public even before full trials were completed. It is still awaiting approval from the World Health Organization.


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