U.S. regulators have authorized a fourth dose of Pfizer-BioNTech’s COVID-19 vaccine for Americans 50 and older because of concerns about waning immunity in the age group, the drugmakers said on Tuesday.
U.S. regulators have authorized a fourth dose of Pfizer-BioNTech’s COVID-19 vaccine for Americans 50 and older because of concerns about waning immunity in the age group, the drugmakers said on Tuesday.