PARIS (NYTIMES) - The Dutch can now invite only two guests to their homes as part of a new lockdown. In Denmark, where masks and other social restrictions had all but disappeared thanks to a successful vaccination campaign, cinemas, amusement parks, zoos and other establishments are closed once again.

By contrast, France has ruled out lockdowns, curfews or closures on a continent where new Covid-19 rules are being announced every day in the face of the Omicron variant's rapid spread. "The French exception", the front page of newspaper Le Parisien, said on Monday (Dec 20).

For now, France - as well as Spain and, to a lesser extent, Italy - is betting that high vaccine and booster coverage, along with earlier restrictions it put in place, will be enough to keep the coronavirus variant manageable, adopting a wait-and-see attitude as a sense of urgency grips the Netherlands, Denmark and Britain.

The numbers show why.

In London, the number of Covid-19 cases rose by 30 per cent last week, and the mayor declared a "major incident" - an emergency status that frees up resources. Denmark is now recording more than 9,000 new cases daily, one of the highest infection rates in the world.

And the Netherlands became the first country in Europe to return to a full lockdown amid fears that its relatively low number of intensive care unit beds would be overwhelmed.

Spain, Italy and France all have lower Covid-19 cases per 100,000 people than some of their northern neighbours, at least for now.

Dr Antoine Flahault, director of the Institute of Global Health in Geneva, said that countries in northern Europe had "tended to be more proactive, in moving quickly in not wanting their hospitals to be overwhelmed". For countries in the south, he said, restrictions and lockdowns are "always an act of last resort".

In all the countries, economic and political concerns - just days before Christmas - are also guiding governments, amid uncertainty about just how big a risk the variant poses. Public health researchers have warned that even if Omicron is eventually shown to cause less severe illness, its rapid spread could still send huge numbers of people to hospitals.

The warnings recall some of the most uncertain moments early in the pandemic, with surging case numbers leaving European nations with the prospect of a second consecutive Christmas clouded by lockdown-like measures, travel bans and fears of rationed health care.

Governments are accelerating booster shots as the scientific evidence accumulates that two vaccine doses are insufficient to stop infection, though the vaccines appear to reduce the risk of hospitalisation and serious illness. The United States is carefully watching Britain and Denmark for clues of what might happen at home, since both countries are good at tracking variants.

In France, the government said that Omicron was now estimated to have caused hundreds of cases and that it would be the dominant variant by early next month. An average of 52,471 coronavirus cases per day were reported in France in the past week, according to a New York Times database, up 23 per cent from the average two weeks ago.

The government of President Emmanuel Macron has encouraged vaccinations by issuing health passes to people who receive shots and has managed to keep schools and most establishments open. More than 70 per cent of the French population has received two doses, though some six million have yet to receive a single shot.

Fresh restrictions would chip away at that success just four months before presidential elections.

The government is focused on tightening restrictions on unvaccinated people in the new year by making France's health pass contingent on getting vaccinated. Currently, people can also obtain a pass with a recent negative Covid-19 test.

The government has also shortened the wait before people can receive a booster shot to four months, from five. So far, about 17.5 million people have had boosters, or about 36 per cent of the population that had received two doses.

"It's annoying, but this year there's at least more of a Christmas spirit than last year, when we had a curfew," said Ms Sherryline Ramos, a student in communications who was strolling with a friend along the Champs-Elysees in Paris. "We couldn't go out and enjoy Christmas decorations.''

In Spain, there has also been little appetite to return to the restrictions that became common during previous waves of the virus. Such a move, before the Christmas holiday, is considered both politically and economically treacherous.

Last week, officials raised the country's alert level, and they now report 50 infections per 100,000 people, the steepest rate in months. But Monday, Prime Minister Pedro Sanchez signalled a wait-and-see approach, noting that hospitalisations remained lower than elsewhere in Europe and that the vaccines appeared to be doing their job.

"With notably higher contagion figures, we have lower hospitalisation and intensive care occupation than a year ago," he said. "The first conclusion is that vaccination works and that this health crisis can only be stopped by science."

Medical experts agree that Spain's high vaccination rates have set it apart from other European countries. More than 80 per cent of the country is fully vaccinated.

But some in the public health community expressed reservations about the government's current approach. Mr Rafael Vilasanjuan, policy director of ISGlobal, a public health think tank in Barcelona, said that as countries in northern Europe move urgently to try to slow the variant, Spain could be losing valuable time in getting ahead of it.

"We're not in the situation where we can think the vaccine is enough," he said. "We can eventually be in the same situation as others with hospitalisations."

Mr Vilasanjuan said the country should be considering a number of measures that other nations have adopted, including instituting a national vaccine passport and more forcefully pushing citizens to avoid large meetings, even during the holidays.

He noted that while Omicron numbers had not surged yet to the levels seen in some other countries, they had risen in cities like Barcelona, where they now account for nearly one-third of polymerase chain reaction tests in some hospitals.

Dr Jose Martinez Olmos, a former Spanish health official who works now as a professor at the Andalusian School of Public Health in Granada, said that voluntary measures might not be enough in the long term. He said the government might soon need to impose new restrictions on public activities, like limiting capacity in restaurants, hotels and theatres, and reducing their hours of operation.

And, as hard as it might be to enforce in Spain, the government needs to encourage limits on Christmas activities, Dr Olmos said. "They need to recommend that people going to Christmas dinners try to be inside as little as possible, because social interactions are the key risk," he said.

In Italy, the government is considering imposing new measures amid concerns over Omicron, but Prime Minister Mario Draghi said on Monday that a final decision had not been made.

The government has made the vaccination campaign a national priority.

In October, Italy became the first major European country to require a "Green Pass" for all workers. Since then it has continued to tighten restrictions for the unvaccinated. As at last week, people travelling to Italy from other European countries must show recent negative rapid tests and proof of vaccination or recovery, or else they may be quarantined.

Omicron's rapid spread - especially in Britain and Denmark, two countries with high vaccination rates - has alarmed many experts.

Denmark lifted all social restrictions in early September after a successful vaccination campaign. But last week, in addition to closing a host of public venues, the government banned the serving of alcohol from 11pm to 5am and required a valid vaccine passport for travel aboard intercity buses and trains.

In the Netherlands, concerns over Omicron's effects on the health care system pushed the government over the weekend to order the closure of all but essential businesses until the second week of January. The number of guests allowed into people's homes was limited to two, though four will be allowed on Christmas and New Year's Eve.

Mr Michel de Blaeij, 33, who lives in Terneuzen, a city in the south of the Netherlands, said he supported the measures, but he was critical of what he considers the government's lack of clarity and consistency. The government's decision to send schoolchildren home on Christmas vacation a week early had left many parents scrambling, he said.

"You just don't know where you stand," he said, adding, "The general mood is frustration right now."