A single dose of Pfizer coronavirus vaccine (PFE.N) may not generate a sufficient immune response to protect against dominant new variants, except in people who have already been infected with COVID-1
The Imperial College study, which looked at immune responses among healthcare workers in Britain after their first dose of the Pfizer shot, found that those who had previously had a mild or asymptomatic infection improved their defenses against more infectious mutated variants. appeared in Britain and South Africa.
But the immune response after the first dose of the shot is weaker in people who have not been previously infected, potentially putting them at risk for such options, say researchers leading the study.
“This study emphasizes the importance of receiving a second dose of the vaccine to protect the population,” said Rosemary Boyton, a professor of immunology and respiratory medicine at Imperial who led the study.
“People who have received their first dose of the vaccine and who have not previously been infected with SARS-CoV-2 are not fully protected against the circulating ‘concerns’.”
The study, published in the journal Science, analyzed blood samples for the presence and levels of immunity against the original strain of SARS-CoV-2, as well as a so-called UK variant known as B.1.1.7 and another known as B.1.351 , originated in South Africa.
It was found that after the first dose of Pfizer vaccine, an enhanced immune response in the form of T cells, B cells and neutralizing antibodies was associated with a previous infection.
However, in people who did not have COVID-19, a single dose of the vaccine resulted in lower levels of neutralizing antibodies against the original virus and its mutant variants.
Danny Altman, the Imperial professor of immunology who led the study, said it meant there would be a “window of vulnerability” for people between their first and second doses.
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