Pfizer Inc. and partner BioNTech SE have pushed back plans to request authorization of their Covid-19 vaccine in children ages 2 to 5, after the shot generated a weaker than expected immune response in a key study.
The companies said Friday they would begin testing the addition of a third dose in the children, and if successful, would ask U.S. health regulators to authorize use sometime during the first half of 2022.
