The US Food and Drug Administration has issued emergency authorization for a booster shot of the Pfizer-BioNTech coronavirus vaccine. Those eligible to receive the third jab must be 65 years or older or those 18 or older at high risk of severe illness or exposure to the virus.
The FDA gave the emergency use authorization on Wednesday.
The US government announced plans last month to launch a booster campaign, saying the efficacy of coronavirus vaccines likely wanes over time.
Last week, an FDA panel of experts recommended booster shots for elderly people and the high-risk groups on grounds that the benefits would outweigh risks. The high-risk groups include healthcare workers.
The FDA says the booster dose will be administered at least six months after a second shot of the Pfizer vaccine.
The FDA has already given full approval to two doses of the vaccine. The third jab's emergency use authorization allows it to be available during public-health emergencies.
US pharmaceutical firm Moderna has also applied for the authorization for a third dose of its coronavirus vaccine.