Fourth Pfizer Shot Boosts Protection From Covid, Study Shows

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.

The rate of severe illness among those who received a fourth dose was about three times lower than those who had received only a third dose, and the protection didn’t decline throughout the eight-week study period.

In addition, people ...