Vaccine maker Pfizer said Friday that trials of its vaccine in children ages 2 to 5 show that it did not provide the expected immunity in kids this age, and it is adding a third dose to the regimen.

U.S. health authorities again expanded the nation's booster campaign Thursday, opening extra doses of Pfizer's COVID-19 vaccine to several million 16- and 17-year-olds. The U.S. and many other nations ...

A third dose of the Pfizer/BioNTech COVID-19 vaccine can "strongly" boost protection against the delta variant -- beyond the protection afforded by the standard two doses, suggests new data released ...

NEW YORK, N.Y. — Pfizer announced Wednesday that data shows a third dose of its COVID-19 vaccine can “strongly” boost protection against the highly transmissible delta variant. The pharmaceutical and ...