Some Americans across the US are getting the first doses of the Pfizer-BioNTech Covid-19 vaccine today.
But the milestone comes as the coronavirus pandemic is surging across the country.
The United States reported more than 109,300 current Covid-19 hospitalizations on Sunday, setting a new record high since the pandemic began, according to the Covid Tracking Project.
And the US is also nearing 300,000 coronavirus deaths since the pandemic began.
Experts are urging Americans to not let up their guards despite today's good vaccine news. Remember: It will be several months before most Americans can get a Covid-19 vaccine.
The director of the National Institutes of Health warned that even those who get the vaccine should keep wearing masks for the foreseeable future.
"You still need to think of yourself as potentially contagious even though you are protected from getting sick at a very high percentage of certainty," Dr. Francis Collins told NBC's "Meet the Press."