The United Kingdom is temporarily closing off all travel corridors starting Monday, Jan. 18, Prime Minister Boris Johnson announced Friday .

Concerned about the spread of COVID-19 as well as “yet unidentified new strains” of the virus, Johnson said the ban will be in place until at least Feb. 15, although anyone flying into the country from overseas can show proof of a negative COVID test and be allowed in.

A new strain of the virus was first discovered in England last month, and although it is not more deadly than the first strain that breached the entire world, it is more contagious. The latest government figures on Friday showed another 55,761 new cases had been reported, up from 48,682 the previous day.

“It’s vital to take extra measures now when day by day we are making such strides in protecting the population,” Johnson said. “It's precisely because we have the hope of that vaccine and the risk of new strains coming from overseas that we must take additional steps now to stop those strains from entering the country."

All travel corridors will close Monday. After that, arrivals to the UK will need to quarantine for up to 10 days unless they test negative after five days. Johnson said that once the most vulnerable have been vaccinated by mid-February "we will think about what steps we could take to lift the restrictions.”