Britain is tightening border controls to prevent new strains of COVID-19 coming into the country, suspending all the ‘travel corridor’ arrangements that had meant arrivals from some countries did not need to quarantine.

Axar.az reports that the change comes into force at 0400 GMT on Monday and means all passengers must have a recent negative coronavirus test and transfer immediately into isolation upon arrival. The isolation period lasts for 10 days unless the passenger tests negative after five days.

Prime Minister Boris Johnson made the announcement during a news conference when he praised the country’s vaccination program, but he also warned: “What we don’t want to see is all that hard work undone by the arrival of a new variant that is vaccine busting.”

On Thursday, Britain banned arrivals from South America, Portugal, and some other countries over fears about a strain of the virus detected in Brazil.