More than 500,000 people have died from COVID-19 in the United States since the pandemic began, according to Johns Hopkins University on Monday, by far the highest reported toll of any country.

The catastrophic US figure comes as some signs of hope are emerging in the world's hardest-hit country, with millions of people now vaccinated and winter's massive spike in infections dropping.

Still, the grim threshold was reached only about a month after the US recorded 400,000 fatalities from the disease in mid-January, with cases now on the decline but deaths continuing to mount.

The toll, 500,071, is more than double the number in absolute terms of reported deaths in Brazil, which has the world's second highest toll.

After the first COVID-19 death was announced in the US in February 2020 it took about three months to pass the 100,000 mark, during a first wave that hit New York particularly hard.

It took another four months to reach 200,000 fatalities, and just under three more months to reach 300,000.

Cases surged into the winter season which brought people indoors for holiday gatherings. The total reported number of known infections was over 28 million on Monday.

But deaths are still coming, and President Joe Biden last month warned that "well over" 600,000 people in the US could die from the virus.

According to the US Centers for Disease Control and Prevention (CDC), more than 61 million people have received at least one shot of vaccine in the United States, with some 18 million getting the full two doses.

Biden has made it a priority to get 100 million people vaccinated within the first 100 days of his administration.