According to a new study published Thursday, the effectiveness of the Pfizer-BioNTech vaccine against Covid-19 declines faster than that of the AstraZeneca jab.
“Two doses of Pfizer-BioNTech have higher initial effectiveness against new COVID-19 infections. But this tapers off faster compared to two doses of Oxford-AstraZeneca,” said Oxford University researchers.
The study, which has not been peer-reviewed, is based on a survey by Britain’s Office for National Statistics. It carried out CRP tests from December last year to this month in randomly selected households.
It found that “the dynamics of immunity after the 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 load and symptomatic infection” when looking at a period of several months after complete vaccination. However, rates remained low for both injections.
The study findings come when Israel administers booster injections after giving 58 percent of the population two injections of the Pfizer jab.
The United States is also ready to offer booster vaccines to increase antibody levels following concerns about decreased effectiveness of the Pfizer and Moderna vaccines.
The Oxford research also found that protection was greatest among those who had already been infected with the virus.
The study examined two groups of more than 300,000 people over 18, first during the period dominated by the Alpha variant, which emerged in Kent, south-eastern England. The second from May 2021 onwards, when the variant Delta has been dominant.
He confirmed that the vaccines are less effective against Delta, which was first seen in India.
The AstraZeneca vaccine is the most widely offered in the UK. In contrast, those under 40 are offered Pfizer or Moderna due to blood clotting problems.