The Delta coronavirus variant -- the B.1.617.2 variant first identified in India – is quickly spreading across the United States, US surgeon general said.
"I'm worried about those who are unvaccinated," US Surgeon General Vivek Murthy told CNN, noting the Delta variant "is rapidly increasing here in the United States."
He also added that the new variant "appears to be significantly more transmissible than even the Alpha variant or the UK variant, which is now dominant in the United States."
The warning by Murthy comes as the pace of vaccinations across the US is falling, leaving unvaccinated Americans vulnerable to new variants.
"The key is get vaccinated, get both doses," Murthy added.
As of Tuesday, 43.9% of the total US population was fully vaccinated while 52.6% has received at least one dose of a vaccine, according to the CDC.
Last week, the Director of the United States National Institute of Allergy and Infectious Diseases Anthony Fauci also announced during a White House COVID-19 briefing that spread of the Delta variant in the United Kingdom could be repeated in the US if people don't get vaccinated.
"We cannot let that happen in the United States, which is such a powerful argument to underscore what Dr. (Rochelle) Walensky said, to get vaccinated, particularly if you've had your first dose, make sure you get that second dose," Fauci said in a White House Covid-19 briefing. "And for those who have been not vaccinated yet, please get vaccinated. This is the national month of action."
He also reiterated that the Delta variant "may be associated with an increased disease severity, such as hospitalization risk, compared to (the Alpha variant, B.1.1.7)."