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More than 600,000 deaths have been reported in the United States from COVID-19, according to a tally by Johns Hopkins University, marking a grim milestone even as a nationwide push for vaccinations appears to have curbed the worst of the pandemic’s toll among Americans.

Nearly four months have passed since U.S. topped 500,000 deaths in late February, a sign of a nationwide death rate that has slowed to levels not seen since the earliest weeks of the pandemic in March 2020. By comparison, it took just over one month for the U.S. death toll to surge from 400,000 to 500,000 this past winter.

As hospitalizations and deaths from COVID-19 in the U.S. have continued to drop, a growing number of states are moving to end many of the public health measures imposed to curb the pandemic. Touting more than 8 in 10 eligible residents with at least one dose of vaccine, Vermont’s Governor Phil Scott said Monday the state would end all its COVID-19 restrictions.

“It is safe because Vermonters have done their part to keep spread of the virus low throughout the pandemic and stepped up to get vaccinated. In fact, no state in the nation is in a better or safer position to do this than we are,” the governor said in a statement.

Behind Vermont, just 13 states and the District of Columbia have so far gotten at least one dose to at least 70% of their adult residents. Close to 65% of all American adults have at least one dose nationwide.

But the pace of vaccinations has slowed. Only around 350,000 Americans are getting their first dose of COVID-19 vaccine daily, according to recent figures from the Centers for Disease Control and Prevention — the lowest recorded pace of shots since vaccination efforts first ramped up at the end of 2020.

And the once-plummeting rate of new U.S. deaths from COVID-19 also appears to have slowed in recent weeks, as cases continue to spread mostly among non-vaccinated people.

U.S. health officials have also stepped up their warnings over faster-spreading variants of SARS-CoV-2, the virus that causes COVID-19. While studies suggest all of the currently authorized vaccines in the U.S. remain effective against all “variants of concern,” federal health officials have warned of lower effectiveness in those who have not yet gotten their second dose.

On Monday, the CDC joined other public health organizations around the world in classifying the so-called Delta variant, first spotted in India, as a “variant of concern,” instead of merely a “variant of interest.” Projections published by the CDC on Tuesday estimate the strain has surged to account for about 1 in 10 cases in the U.S., up from less than 3% at the end of May.

“We’ve made enormous progress in the United States. Much of the country is returning to normal, and our economic growth is leading the world, and the number of cases and deaths are dropping dramatically. But there’s still too many lives being lost,” President Biden said Monday in Belgium, after meetings with allied leaders on the pandemic and other global challenges.

“We have more work to do to beat this virus, and now is not the time to let our guard down. So, please — please get vaccinated as soon as possible. We’ve had enough pain,” the president said.