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The study, which has not been peer-reviewed, is based on the results of a survey by Britain's Office for National Statistics that carried out PCR tests from December last year to this month on randomly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.