• According to a U.K. study, a single dose of Pfizer Inc (NYSE: PFE) - BioNTech SE's (NASDAQ: BNTX) coronavirus vaccine may not generate a sufficient immune response to protect against dominant new variants, except in people who have already been infected with COVID-19, reports Reuters.

• The Imperial College-led study, which analyzed blood samples among healthcare workers after their first dose of the Pfizer shot, found that those who previously had the infection showed better protection against virus variants found in Britain and South Africa.

• After a first dose of the shot, the immune response was weaker in people who had not previously been infected, potentially leaving them at risk from such variants, researchers leading the work said.

• It was observed that, after a first dose of the Pfizer vaccine, a boosted immune response in the shape of T-cells, B-cells, and neutralizing antibodies was associated with prior infection.

• The study highlights the importance of getting second doses of the vaccine rolled out to protect the population. There would be a "window of vulnerability" for people between first and second doses.

• Price Action: BNTX shares are up 6.6% at $191.50, while PFE shares are down 0.01% at $38.59 during the market trading session on the last check Friday.

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