The US Food and Drug Administration on Monday gave full approval to the COVID-19 vaccine made by Pfizer and German partner BioNTech for use in people over the age of 16.
It's the first such approval of a COVID-19 shot.
The vaccine has been authorised for emergency use since December and more than 204 million people in the United States have received it, based on Sunday's data.
But none of the three authorised COVID-19 vaccines had previously received full FDA approval.
Public health officials hope it will convince more unvaccinated Americans that Pfizer's shot is safe and effective.
Vaccine hesitancy among some Americans has hindered the United States response to the novel coronavirus.
"While millions of people have already safely received COVID-19 vaccines, we recognize that for some, the FDA approval of a vaccine may now instill additional confidence to get vaccinated," said Janet Woodcock, the US Food and Drug Administration's acting commissioner.
Roughly 51 per cent of Americans have been fully vaccinated so far, even as a recent surge of infections spurred by the contagious Delta variant ravages parts of the country with low vaccination rates.
SpaceX's massive Starship spacecraft exploded in space on Thursday minutes after lifting off from Texas, prompting the FAA to halt air traffic in parts of Florida, in the second straight failure this year for Elon Musk's Mars rocket program.
Fighters linked to Syria's ousted leader Bashar al-Assad mounted a deadly attack on government forces on Thursday, authorities said, in some of the worst violence against the government since rebels seized power.
A Russian missile struck a hotel in the central Ukrainian city of Kryvyi Rih late on Wednesday, killing four people and injuring 31, with rescuers still searching on Thursday morning for anyone trapped in the rubble, officials said.
The United States broke a long-standing diplomatic taboo by holding secret talks with Hamas on securing the release of US hostages held in Gaza, sources told Reuters on Wednesday, while US President Donald Trump warned of "hell to pay" should the Palestinian group not comply.