The U.K. is preparing for a new wave of COVID-19 cases as the Omicron variant is doubling every three days.

With a daily average of about 47,000 new coronavirus cases and 817 confirmed new Omicron cases as of Thursday, the U.K. has become a guinea pig for countries as they brace themselves for what to expect from the new variant.

“We expect to see at least 50% of COVID-19 cases to be caused by the Omicron variant in the next two to four weeks,” the U.K. Health Security Agency said.

About 77% of Britain’s population has at least one dose of the COVID-19 vaccine while 70% is fully vaccinated.

How Britain fares against Omicron will offer clues to the U.S. and the rest of the industrialized world about how the variant behaves in a highly vaccinated population, how sick those who are infected get and if its dozens of mutations have given Omicron enough of an advantage on the evolutionary ladder to starve Delta of the hosts it needs to stay on top, The Wall Street Journal noted.

While countries begin to battle new outbreaks, health officials remain uncertain whether this variant presents a different severity profile and whether it could escape protection against immunity induced by vaccines and previous infections.

What is known is that symptoms of the new Omicron COVID variant are said to be “extremely mild,” according to the South African doctor who first identified patients with the virus strain.

Hospitalization rates have not seen a dramatic increase in Britain, with a weekly average of 7,300 as of Tuesday. The weekly average of COVID-related deaths remains at about 170.

John Edmunds, an epidemiologist at the London School of Hygiene and Tropical Medicine and a member of the government’s Scientific Advisory Group for Emergencies, told a Royal Society of Medicine webinar on Thursday that it is “extremely likely” that the number of Omicron cases is higher than what has been confirmed.

“Nobody wants to have to reintroduce these measures. It’s very damaging for parts of the economy – the hospitality and retail sector, in particular, are going to be affected – but unfortunately, we have to do it,” he said.

“With the speed of spread of this virus, we may well have really significant numbers of cases by Christmas,” he added. “I suspect that whatever we do now, we are unlikely to overreact.”