VIENNA — As Austria’s mandate requiring all adults to be vaccinated against the coronavirus comes into force this week, debate is still bubbling over its legality, public health benefits and enforcement, in a rollout closely watched by other nations mulling whether to follow suit.

As the first Western democracy to bring in a sweeping mandate, Austria is seen as a test case for other countries grappling with how to deal with those who refuse to get vaccinated — and it has gotten off to a stuttering start.

The new law comes into force Friday, but following logistical hurdles as the start date approached, the government opted to roll out its plans in three phases. During the first, those who aren’t vaccinated are given the “opportunity” to fulfill the legal obligation.

From mid-March, there will be spot checks and fines of up to 670 euros ($752), and at some unspecified date, medical data will be used to issue penalty notices. Those are income dependent and could stretch to 3,600 euros ($4,000).

But as pressure eases on hospitals because of the less-severe omicron variant and questions remain over whether a full mandate will be enforced to any meaningful degree, health experts and politicians across Europe are divided on whether the law makes sense.

Amid this fraught debate, which also raises questions of civil liberties and security, European countries have enacted various strategies for how to close their gaps in vaccination.

In France, President Emmanuel Macron has declared that his strategy is to “piss off” the unvaccinated. Italy has mandated vaccines for those over 50 and Greece for those over 60. Germany’s parliament is debating a mandate.

In the Czech Republic, the new government has said it will change a law to vaccinate seniors so as not to “exacerbate divisions in society.”

Seventy-five percent of the population in Austria is fully vaccinated, a few points ahead of countries such as Germany and Britain, but lagging places such as Spain, which has reached a rate of 80 percent. That compares with 64 percent in the United States, according to Johns Hopkins data.

“There’s absolutely no doubt that the vaccine mandate is a necessity,” Austria’s conservative chancellor, Karl Nehammer, said at a news conference last month.

But not all are in agreement. When Austria announced its full mandate in November, its intensive care units were under strain from a vicious wave of infections from the delta variant and the country was heading into a new lockdown. Now, infection levels are at their highest point of the pandemic, but hospitalizations and deaths have eased as the omicron variant has become dominant.

Gerald Gartlehner, a prominent Austrian epidemiologist at Danube University, Krems, has called on the government to reassess the measure. He said he had supported a mandate during the delta wave.

“Since then, I think the reality has really changed,” he said. When the omicron wave is over, it is possible the population will have a level of immunity it hasn’t had before, he said. Earlier this month, the World Health Organization warned that omicron was set to infect every second European.

“I don’t think a mandate is necessary anymore,” Gartlehner said.

A partial mandate for older people would “still make sense,” he said, as would waiting to have the obligation begin in the fall, ahead of winter, and allowing more time for preparations.

He also criticized “contradictory” government policies that will see an easing of rules in mid-February, which will allow the unvaccinated to do things such as eat at restaurants. Meanwhile, spot fines will not have kicked in yet, meaning there will be less pressure for people to get vaccinated initially at least, he said.

Although the mandate is “coming too late” to stop the omicron variant, “that doesn’t mean the effort is futile,” said Peter Klimek, a professor at the Medical University of Vienna and adviser to the government. “It’s a preparation for the rest of the year, and for the future.”

Vaccines still offer strong protection against hospitalization and death, data shows, and similar to influenza vaccines, coronavirus vaccines will be adapted to new variants, said Monika Redlberger-Fritz, of the Medical University of Vienna’s virology center.

“We have to remember, omicron won’t be the last variant,” Redlberger-Fritz said. “There will be many more to come.”

The mandate covers anyone over 18 aside from pregnant people (though the vaccine is recommended for them, too), those with medical reasons and anyone who has tested positive for the coronavirus in the past six months.

There are questions over just how many will hold out. Sixty-two percent of Austrians support a mandate, said Peter Hajek, head of Public Opinion Strategies in Vienna, citing the firm’s latest polling. Of those, 17 percent think it shouldn’t happen yet. Thirty-five percent are opposed.

Of those who say nothing will make them get the vaccine, “they will have to consider whether 3,600 euros is something they want to pay,” Hajek said.

It remains unclear when such fines might be issued.

The agency managing the country’s centralized vaccine database said last month that it won’t be able to update the database with information on exemptions for at least two months after the law is in effect, saying it had not been consulted over preparations.

In Germany, where Chancellor Olaf Scholz has said that he sees a compulsory mandate as the only way out of the pandemic, the administrative hurdles are even bigger, as there is no centralized health database.

As lawmakers debate a range of potential measures, Bundestag Vice President Wolfgang Kubicki, of the liberal Free Democrats, has been a leading voice opposing a mandate.

“Can preventing a seasonal systemic burden [on the health-care system] be a sufficient reason for widespread, massive restrictions on fundamental rights?” he wrote in a recent op-ed. “Hardly likely.”

But Carsten Watzl, a professor in immunology at the University of Dortmund, said that the approximate 2 million unvaccinated people over 60 remain a particular concern.

“If those people were to get infected, even with omicron, we could get into trouble,” he said, and it’s not a given that future variants might be less severe. What remains an unknown, however, is how many of the unvaccinated have immunity through infection, Watzl said.

“The question is how much political head wind do you get for a full mandate versus one for those above 50 or 60,” he said.

Already in Germany, there are nearly 400,000 people marching each week, and security officials say they fear a mandate could trigger a backlash from the extremist fringe, with threats against public officials and doctors on the rise.

Any rollout in Germany is likely to be accompanied by questions of data privacy, he said, and asking employers to do checks would not find acceptance.

If there’s no proper enforcement mechanisms for a mandate, “it does more damage than good,” Watzl said.

The mandate also could face legal challenges. In Austria, an already understaffed justice system said it would need 200 new staff members to deal with the expected onslaught of 133,000 additional, mandate-related court cases. And questioning a full mandate by some experts could add weight to the arguments of those who oppose the ban.

Heinz Mayer, a constitutional expert and former dean of the law faculty of the University of Vienna, said in November that the situation in hospitals was so “catastrophic” that he did not foresee any constitutional issues for a mandate.

In the current situation, though, he said he can’t accurately judge because he would need to know the exact details of medical evaluations and other data. The weight of the statements, in general, seemed to be on the side of those “saying that a vaccine mandate is the only way to get us into a position where we can effectively fight the pandemic,” Mayer said.

Depending on how the pandemic develops, a “milder measure” than a full mandate could be judged sufficient, he said.

At a recent demonstration in Vienna to oppose the mandate, 51-year-old Bernhard, who declined to give his last name as he said he works as a civil servant, said he would be among those lodging a challenge.

“I’ll fight this mandate with every legal option I have,” he said, holding a megaphone he used to yell, “Resistance!”

Morris reported from Berlin.