Dr. Anthony Fauci is again reminding Americans of the importance of securing high vaccination numbers when it comes to the fight against variants.

During a press conference on Tuesday, Fauci turned the proceedings to a topic he said has gained “a lot more attention” in recent days, i.e. variants. More specifically, Fauci pointed to the current situation surrounding the so-called “Delta” variant. First detected in India, the Delta variant—as seen in the latest CDC data—is currently responsible for more than six percent of all infections in the U.S. In the U.K., meanwhile, the Delta variant is already widely considered the dominant strain after experiencing rapid spread.

“In the U.K., the Delta variant is rapidly emerging as the dominant variant, greater than 60 percent,” Fauci said Tuesday. “It is replacing the B.1.1.7. … We cannot let that happen in the United States.”

Fauci, who serves as both the director of the National Institute of Allergy and Infectious Diseases and the chief medical advisor to President Biden, coupled this message of caution by again emphasizing the role vaccinations play in this ongoing struggle.

“Get vaccinated,” he said. “Particularly, if you had your first dose, make sure you get that second dose. And for those who have not been vaccinated yet, please get vaccinated.”

On Wednesday, the U.S.—according to data from Johns Hopkins University—was confirmed to have averaged the lowest number of daily COVID-19 infections and deaths since March of last year. Still, some concern remains regarding the rate of vaccinations in the U.S. 

The most recent data, per the CDC, shows that 140.4 million people in the U.S. are now fully vaccinated. If you’re not yet one of those 140.4 million people, then do yourself and everyone around you the small favor of making a vaccine appointment.