It’s not clear whether a more transmissible variant of the coronavirus that prompted tighter restrictions in the U.K. has made its way to the U.S., according to Moncef Slaoui, chief scientific adviser for the government’s vaccine acceleration program.

“We don’t know,” Slaoui said on CNN’s “State of the Union.” on December 20. “We’re looking at that.”

Assistant Secretary for Health Brett Giroir questioned the threat posed by the virus changes cited by the U.K. government, saying the coronavirus blamed for Covid-19 has mutated more than 4,000 times since its discovery. There’s no imminent need to suspend flights from the U.K., he said on ABC’s “This Week.”

“We don’t know that it’s more dangerous, and very importantly we have not seen a single mutation yet that would make it evade the vaccine,” and while that can’t be ruled out for the future, “I don’t think there should be any reason for alarm right now,” Giroir said.

The new variant may be as much as 70% more transmissible, which led U.K. Prime Minister Boris Johnson to announce a lockdown for London and large parts of southeast England on December 19. He canceled plans to ease pandemic restrictions for five days over the holidays, and banned household mixing in London and the southeast while restricting socializing to just Christmas Day across the rest of England.

Vaccinate Trump?

Even if the variant does become more widespread, Slaoui said the vaccines that are now rolling out will provide protection against it. That includes the Moderna Inc. vaccine that received approval from U.S. regulators on December 18, and Slaoui said the first shots are expected to be administered on December 21.

Giroir, a member of the White House coronavirus task force, urged President Donald Trump to get vaccinated against Covid-19 to promote acceptance of immunization among his supporters.

“Again, we have every reason to believe that these two vaccines are very effective and they are safe,” he said. “So I would encourage the president to get a vaccine for his own health and safety, and also to generate more confidence among the people who follow him so closely.”

Vice President Mike Pence and his wife Karen Pence received the coronavirus vaccine developed by Pfizer Inc. and BioNTech SE in a televised event at the White House on December 18.