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.

(AP) - The fall COVID-19 vaccine season is starting slowly for Pfizer, with U.S. sales of its Comirnaty shots sinking 25% after federal regulators narrowed recommendations on who should get them.