Study: Pfizer & AstraZeneca Vaccine Effective Against Delta Variant Of COVID-19

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The study, conducted by Public Health England researchers and published in The New England Journal of Medicine, was conducted by analysing the data of the recipients of both vaccines in the UK. It found that the vaccines' effectiveness against Alpha and Delta to be virtually similar after two doses.

According to its statistical findings, it was found that Pfizer's vaccine is 88% effective at preventing symptomatic disease from the Delta variant, as compared to 93.7% against Alpha. These numbers broadly concur with previous figures which were made with a markedly smaller sample size.

As for AstraZeneca, the vaccine was reportedly 67% effective against the Delta variant, while effectiveness against Alpha stood at 74.5%. These numbers seem lower than expected, but ought not to deter public confidence in the British-made vaccine as the efficacy was previously reported to be 60% and 66% respectively.

"Only modest differences in vaccine effectiveness were noted with the Delta variant as compared with the Alpha variant after the receipt of two doses," wrote the Public Health England researchers.

When analysing the effectiveness after one dose, the difference in protection against Alpha and Delta variants are significant.

The study stated that one dose of Pfizer will only provide 36% efficacy against Delta, whereas AstraZeneca is roughly 30% effective.

"Our finding of reduced effectiveness after the first dose would support efforts to maximise vaccine uptake with two doses among vulnerable groups in the context of circulation of the delta variant," the researchers wrote at the study's conclusion.

Taken into context, Delta – a mutation of the original SARS-CoV-2 virus strain which originated in India around December 2020 and is now dominant in the UK – has caused the number of new cases there to skyrocket. The daily numbers of new cases has hovered around the 50,000 mark for the last week, despite achieving a respectable 68% of the population fully vaccinated.

This was after the UK government decided to implement a strategy of maximising first doses of vaccines to as many people as possible. To date, 46.2 million of its population has received their first dose, while only 35.7 million have received both shots.