The United States government has authorised Johnson & Johnson's single-dose Covid-19 vaccine, enabling millions more Americans to be vaccinated in the coming weeks and setting the vaccine up for additional approvals around the world.

The J&J vaccine is the third authorised in the United States, following ones from Pfizer/BioNTech and Moderna, both of which require two doses.

President Joe Biden hailed the move but cautioned Americans against celebrating too soon. “Things are still likely to get worse again as new variants spread,” he said in a statement, urging people to continue washing their hands, wearing masks, and maintaining social distancing.

“There is light at the end of the tunnel, but we cannot let our guard down now or assume that victory is inevitable,” he said.