Anthony Fauci, the director of the US National Institute of Allergy and Infectious Disease, said it was too early to declare victory over the coronavirus, despite a falling number of cases.

"We don’t want to declare victory prematurely because we still have a ways to go. But the more and more people that can get vaccinated, as a community, the community will be safer and safer," he told The Guardian newspaper.

He said that the danger of emerging coronavirus variants that can diminish the effectiveness of existing vaccines would persist as long as there was "some degree of activity" around the world. 

The Johns Hopkins University estimates that daily cases have more than halved since the start of this month. The Centers for Disease Control and Prevention says 59.1% of US nationals aged 12 and over had been vaccinated at least once as of last Friday.