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Fourth Pfizer Shot Boosts Protection From Covid, Study Shows

A vial of the Pfizer-BioNTech Covid-19 vaccine.

A vial of the Pfizer-BioNTech Covid-19 vaccine.

Photographer: Kobi Wolf/Bloomberg

A fourth dose of Pfizer Inc.’s Covid-19 vaccine improves protection against infection and severe illness, according to an Israeli study. 

The findings, published Wednesday in the New England Journal of Medicine, were based on data from 1.2 million people ages 60 years and older. About half of the participants had a fourth jab, while the rest had only the third.