A patient receives their COVID-19 vaccine booster during a Pfizer-BioNTech vaccination clinic in Southfield, Michigan, US. [Reuters]
The effectiveness of the Pfizer Inc (PFE.N)/BioNTech SE vaccine in preventing infection by the coronavirus dropped to 47% from 88% six months after the second dose, according to data published on Monday that U.S. health agencies considered when deciding on the need for booster shots.