The US death toll from Covid-19 surpassed 600,000 on Tuesday, although authorities hailed progress towards a return to normality as its world-leading vaccination program promised to turn the page on one of the worst health crises in its history.

The United States has racked up by far the largest national death toll -- ahead of Brazil and India -- after a heavily-criticized early response to the pandemic, but has since organized among the world's most effective vaccine roll-outs.