Oxford University study claims its AstraZeneca Covid vaccine’s effectiveness declines slower than Pfizer competitor

The Pfizer-BioNTech vaccine’s protection against Covid “declines faster” than its Oxford-AstraZeneca competitor, with both less effective against the Delta variant, according to an Oxford University study released on Thursday.

Announcing their findings, researchers from the UK-based university stated that, while the Pfizer vaccine had “greater initial effectiveness” against new infections, it “declines faster compared with two doses of Oxford-AstraZeneca.”

While scientists expressed the need to conduct further investigation into the long-term effects of the vaccines, they suggested that initial findings show “that after four to five months effectiveness of these two vaccines would be similar.”

Alongside their investigation into the speed of decline in effectiveness of the vaccines, researchers found that both the Pfizer and AstraZeneca vaccines are less effective against the Delta variant, which first emerged in India and has since become the dominant strain of concern in many countries.

Despite finding that the protection by the vaccines declines and is less effective against the Delta variant, even in double-jabbed recipients, the Oxford University researchers remained confident that having two doses “remains the most effective way to ensure protection” against the dominant strain.

The study, which is awaiting peer review, looked at two groups of more than 300,000 people over the age of 18 during two time periods, when the Alpha variant was dominant and, from May 2021, when the Delta variant was more prevalent. 

Currently, the AstraZeneca vaccine is the most widely distributed in the UK, with the Pfizer and Moderna doses restricted to under-40s amid concerns about potential side effects, such as blood blotting after the AstraZeneca vaccine.

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