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Thursday, August 05, 2021

New research: What second dose of Pfizer vaccine does that the first doesn’t

The finding strongly supports the view that the second shot should not be skipped, Stanford Medicine said in a press release.

By: Express News Service | New Delhi |
Updated: July 26, 2021 11:27:55 am
A health worker prepares to administer a shot of the Pfizer vaccine against Covid-19. (Reuters Photo/File)

The second dose of a Covid-19 vaccine induces a powerful boost to a part of the immune system that provides broad antiviral protection, according to a study led by researchers at the Stanford University School of Medicine. The finding strongly supports the view that the second shot should not be skipped, Stanford Medicine said in a press release.

The study has been published in Nature. It looked at immune responses to the Pfizer vaccine, with which Stanford Medicine had begun inoculating people in December 2020.

The researchers analysed blood samples from individuals inoculated with the vaccine. They counted antibodies, measured levels of immune-signalling proteins and characterised the expression of every single gene in the genome of 242,479 separate immune cells’ type and status.

Stanford Medicine Professor Bali Pulendran, one of the senior authors, and his colleagues assessed activity among all the immune cell types influenced by the vaccine: their numbers, their activation levels, the genes they express and the proteins and metabolites they manufacture and secrete upon inoculation.

The team selected 56 healthy volunteers and drew blood samples from them at multiple time points preceding and following the first and second shots. The researchers found that the first shot increases SARS-CoV-2-specific antibody levels, as expected, but not nearly as much as the second shot does. The second shot also does things the first shot doesn’t do, or barely does, the release said.

“The second shot has powerful beneficial effects that far exceed those of the first shot. It stimulated a manifold increase in antibody levels, a terrific T-cell response that was absent after the first shot alone, and a strikingly enhanced innate immune response,” Pulendran is quoted as saying.

The vaccine — particularly the second dose — also caused the massive mobilisation of a newly discovered group of first-responder cells. First identified in a recent vaccine study led by Pulendran, these cells barely budge in response to an actual Covid-19 infection. But the Pfizer vaccine was found to induce them.

Source: Stanford Medicine

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