The effectiveness of the Pfizer-BioNTech vaccine against Covid-19 declines faster than that of the AstraZeneca jab, according to a new study published on Thursday.
“Two doses of Pfizer-BioNTech have greater initial effectiveness against new Covid-19 infections, but this declines faster compared with two doses of Oxford-AstraZeneca,” researchers at Oxford University said.
The study, which has not been peer reviewed, is based on the results of a survey by Office for National Statistics (ONS) that carried out PCR tests from December last year to this month on randomly selected households.
It found that “the dynamics of immunity following second doses differed significantly” between Pfizer and AstraZeneca, according to the university’s Nuffield Department of Medicine.
Pfizer had “greater initial effectiveness” but saw “faster declines in protection against high viral burden and symptomatic infection”, when looking at a period of several months after full vaccination, although rates remained low for both jabs.
“Results suggest that after four to five months effectiveness of these two vaccines would be similar,” the scientists added, while stressing that long-term effects need to be studied.
