The European Medicines Agency (EMA) recommended Monday to administer an extra Pfizer-BioNTech COVID-19 vaccine to people with severely weakened immune systems 28 days after the second dose.
The EMA's Committee for Human Medicine assessed data on Pfizer-BioNTech booster shots and concluded that it showed "a rise in antibody levels when a booster dose is given approximately six months after the second dose in people from 18 to 55 years old," the EU regulator said in a statement.
It did not directly advise a third dose for healthy adults.
The scientific body is still evaluating data on Moderna booster shots.
