All remaining Americans who are unvaccinated against COVID-19 and eligible need to get the shots, Dr. Anthony Fauci said this week while warning that a far more serious and transmissible variant of the virus is rapidly spreading across the U.S. and will become the dominant strain in a matter of weeks.

Its the unvaccinated people that were concerned about, the White Houses chief medical adviser said in an interview Wednesday with NBCs Today show . Theyve got to start paying attention to it now because if theyre unvaccinated, theyre at risk.

This delta variant of the coronavirus, which was first found in India and contributed to an outbreak that killed hundreds of thousands of people, currently makes up about 20% of newly diagnosed coronavirus cases in the U.S., Fauci said.