Britain’s Health Secretary Matt Hancock announced on Wednesday that another variation of the novel coronavirus has been detected in two people who were contacts of cases that stemmed from recent travel to South Africa.

Hancock announced the discovery on Wednesday while also listing more areas of England that would enter Tier 4 restrictions.

“Of course the fight against the virus is a global effort and we’re constantly vigilant and looking around the world as part of our surveillance,” he said during a press conference. “And thanks to the impressive genomic capability of the South Africans, we’ve detected two cases of another new variant of coronavirus here in the U.K. Both are contacts of cases who have traveled from South Africa over the past week.”

Britain’s Health Secretary Matt Hancock made the announcement during a briefing on Wednesday.

Hancock said the new variant is “highly concerning” because it “is yet more transmissible and it appears to have mutated further than the new variant that was discovered in the U.K.”

As a result, while researchers continue to study the potential implications of the variant, the U.K. has ordered new cases and close contacts of cases detected in the U.K. to quarantine, and placed immediate restrictions on travel from South Africa.

“Anyone in the U.K. who has been in South Africa in the past fortnight, and anyone who is a close contact of someone who has been in South Africa in the past fortnight must quarantine immediately,” he said, adding that they must restrict all contact “with any person, whatsoever.”

“We all know that 2020 has been a hard year and it’s ending in this festive period, which is going to be very different – after all the efforts we’ve gone to to control this virus, and in many parts of the country this virus is under control – just as we’ve got a tiered system in place that was able to control this virus, we discovered a new, more contagious virus variant that is spreading at a dangerous rate,” he said.

Pfizer has voiced confidence in its vaccine’s ability to protect against the first variant that was discovered in the U.K., citing the mRNA’s “flexibility.” It was not immediately clear how the second variant differed from the first and if it would also be susceptible to the vaccine.