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Pfizer Covid-19 jab declines faster than AstraZeneca: study


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The study, which has not been peer reviewed, is based on the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.

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.

The study’s findings come as Israel is administering booster
shots, after giving 58 percent of the population two shots of the Pfizer jab.

The United States is also set to offer booster vaccines to
boost antibody levels following concerns over declining effectiveness of the
Pfizer and Moderna vaccines.

The Oxford research also found that protection was higher
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, southeast England, and secondly from May 2021 onwards, when the Delta
variant has been dominant. 

It confirmed that vaccines are less effective against Delta,
which was first seen in India.

The AstraZeneca vaccine is the most widely offered in the
UK, while those under 40 are offered Pfizer or Moderna due to blood clotting
concerns.



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