The United States on Tuesday surpassed 600,000 Covid-19 deaths, a benchmark that comes as daily Covid-19 case rates slow and CDC labels the delta coronavirus variant a "variant of concern."

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US surpasses 600K Covid-19 deaths

According to data from Johns Hopkins University, as of Tuesday afternoon, the official U.S. Covid-19 death toll was 600,012, marking the largest number of Covid-19 deaths from a single country and representing roughly 15% of the 3.8 million worldwide deaths officially attributed to Covid-19.

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That number is more than the number of American soldiers killed in action during the Vietnam War, World War I and World War II combined, Axios reports. That death toll is also roughly equal to the number of Americans who died of cancer in 2019.

However, the pace of deaths has slowed significantly in recent months. It took roughly a month for the country's death toll to climb from 400,000 to 500,000, but it has taken about four months to climb further to 600,000, NPR reports.

Daily Covid-19 death rates have also dropped precipitously in the United States. The country currently averages roughly 375 Covid-19 deaths per day, compared with around 3,000 per day in January.

The drop in Covid-19 cases and deaths can largely be attributed to vaccinations, experts say. According to CDC, 52.6% of Americans have received at least one dose of a Covid-19 vaccine, while 43.9% have received all required vaccine doses. That includes 64.6% of American adults being partially vaccinated and 54.6% having received all required vaccine doses.

The virus continues to rage in other parts of the world, however, especially in countries where few people have been vaccinated.

"Until we have this under control across the world, it could come back and thwart all the progress we've made so far," Marcus Plescia, CMO for the Association of State and Territorial Health Officials, said. "I'm worried about the people who are not taking advantage of these vaccines. They're the ones who are going to bear the brunt of the consequences."

CDC labels delta coronavirus variant a 'variant of concern'

Meanwhile, on Tuesday, CDC officials labeled the delta coronavirus variant, which was first discovered in India, as a "variant of concern."

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According to CDC, the delta variant was responsible for 2.7% of Covid-19 cases for the two-week period ending in May 22, but that share increased to 10% for the two-week period ending in June 5.

That rise is "the number one driver for classifying this as a variant of concern," Summer Galloway, a Covid-19 adviser to CDC and executive secretary of the SARS-CoV-2 Interagency Group.

Surgeon General Vivek Murthy said the delta variant "appears to be significantly more transmissible than even the alpha variant or the U.K. variant, which is now dominant in the United States."

Murthy said he's also concerned because "there is some data to indicate that it may in fact also be more dangerous, may cause more severe illness. That still needs to be understood more clearly, but these are two important concerns and they explain in part … why this [has] become the dominant variant in the U.K., where over 90% of cases are the delta variant."

CDC officials emphasized, however, that Covid-19 vaccines are highly effective against the delta variant, and they urged unvaccinated Americans to get vaccinated as soon as possible.

"Even though our case counts are declining and people are getting vaccinated, we still have roughly half our population that is unvaccinated," Galloway said. "We have circulation of a more transmissible variant that is definitely a concern, and our bottom line message here is we want to make sure people are taking this seriously and are getting vaccinated as soon as they’re eligible and it's available to them" (Neuman, NPR, 6/15; Gonzalez, Axios, 6/15; Levin/Bosman, New York Times, 6/15; AP/Modern Healthcare, 6/14; Rabin, New York Times, 6/15; Elamroussi, CNN, 6/16).