The US Food and Drug Administration on Monday gave full approval to the Covid-19 vaccine made by Pfizer Inc and German partner BioNTech SE for use in people over the age of 16, in 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 recognise 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% 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.
The FDA's approval is based on updated data from the company's clinical trial.
"Based on the longer-term follow-up data that we submitted, today's approval for those aged 16 and over affirms the efficacy and safety profile of our vaccine at a time when it is urgently needed," Albert Bourla, CEO of Pfizer, said in a statement.
The Pfizer-BioNTech vaccine will now be marketed under the name Comirnaty, the FDA said.
Some US cities including New York and San Francisco have already imposed rules requiring vaccination to dine at restaurants or work in government offices, among other activities.