The United Kingdom will soon know the extent of the impact expected from the Omicron variant of the novel coronavirus, a government adviser has said.

Mike Tildesley, a professor at the University of Warwick and member of the government's Scientific Pandemic Influenza Modelling group, said on the BBC's Breakfast program scientists should know in days whether the National Health Service can cope with an expected influx of cases in the coming weeks.

He said experts have been crunching the numbers for the variant, which causes a less severe illness but is much easier to catch.

"It does look like we may be in a situation where we're getting cases very, very high," he said. "But there's early evidence that things might be turning around in London."

Tildesley said scientists want to use the modeling to understand whether additional restrictions on people interacting would help.

"The problem, of course, is that if you're thinking about introducing controls, once you're beyond the peak of the infection, then that has much less effect," he said.

Tildesley made the comments as Keir Starmer, the leader of the UK's main opposition, the Labour Party, went into isolation after testing positive for COVID-19.

Starmer was represented in Parliament by his deputy, Angela Rayner, as Prime Minister Boris Johnson was grilled on his handling of the pandemic response.

Johnson has been criticized in some quarters for saying the UK will not introduce additional restrictions, even though the NHS will feel "temporarily overwhelmed".

"We have a chance to ride out this Omicron wave without shutting down our country once again," he said at a news conference on Tuesday.

The Daily Telegraph newspaper reported on Wednesday that the UK will, however, relax some of its testing rules, in a bid to shorten isolation periods and ensure more people can return to work.

The paper said an employee shortage caused by people needing to isolate has become "as big a problem as COVID itself".

The shortages have caused trash collections to be delayed in some places, trains to be cancelled, and some hospitals to suspend non-urgent surgery. Schools have also been hit hard, with around one employee in five missing for this week's start of term.

The paper said asymptomatic people who are shown to have COVID-19 in a lateral flow test will not have to take a follow-up PCR test, something that had delayed the start of isolation periods and therefore prolonged them. People who have symptoms will, however, still need to take a follow-up PCR test.

In an attempt to ensure workers do not isolate unnecessarily, London has also said 100,000 key staff in food processing, transportation, and border services will get daily lateral flow tests, the Guardian newspaper reported.

Additionally, the BBC said international arrivals will no longer need to test negative for COVID-19 two days before landing in the UK.

Elsewhere in Europe, France's President Emmanuel Macron has said he will make life difficult for people refusing a vaccination.

He told Le Parisien newspaper: "I really want to hassle them, and we will continue to do this; to the end."

However, many lawmakers were uncomfortable with his words and the idea of forcing people to have a jab and delayed debate on the issue in the nation's Parliament.

Mandatory vaccinations are also being introduced in other European countries, including Austria and Germany.

The Reuters news agency said Berlin is also considering additional restrictions on social contacts.

Germany's health minister, Karl Lauterbach, told the Redaktions-Netzwerk Deutschland media group: "Tightening will unfortunately be necessary to counter the heavy wave that is coming our way."

Germany recorded 58,912 new infections on Wednesday, which was up 47 percent on the week before but still far fewer than the 218,724 registered in the UK.