The Centers for Disease Control and Prevention (CDC) on Monday warned Americans to avoid any nonessential travel to the United Kingdom (U.K.) due to rapidly rising coronavirus cases.
The "Level 4" warning from the CDC is the agency's highest. The agency recommends that if travel can't be avoided, people should make sure they are vaccinated.
"Because of the current situation in the United Kingdom, even fully vaccinated travelers may be at risk for getting and spreading COVID-19 variants," the advisory notes.
Separately, the State Department also issued its own Level 4 "Do Not Travel" warning.
The warnings come as the U.K. government has lifted most of the country's remaining coronavirus restrictions. Face coverings are no longer required, and physical distancing rules and capacity restrictions have all been lifted.
New cases have skyrocketed in the country in the past month, driven by the highly contagious delta variant. Cases topped 50,000 per day last week for the first time since January, and the seven-day moving average is almost 45,000 cases.
The United States has had an entry ban in place on non-U.S. citizens from the European Union, the U.K. and other countries, though several European countries have recently begun allowing international visitors.
Canada on Monday announced it would begin allowing vaccinated U.S. tourists to visit starting Aug. 9, but the Biden administration currently does not have plans to lift its own restrictions to visitors from that country.