BERLIN (NYTIMES, REUTERS) - The University Hospital of Giessen, one of Germany's foremost clinics for pulmonary disease, is at capacity. The number of Covid-19 patients has tripled in recent weeks. Nearly half of them are on ventilators.

And every single one is unvaccinated.

"I ask every patient: Why didn't you get vaccinated?" said Dr Susanne Herold, head of infectious diseases, after her daily round in the ward on Thursday (Nov 11). "It's a mix of people who distrust the vaccine, distrust the state and are often difficult to reach by public information campaigns."

Patients like hers are the main drivers of a fourth wave of Covid-19 cases in Germany that has produced tens of thousands of new daily infections - more than the country has had at any point in the pandemic.

For Germany, it is a startling turnabout. At the onset of the pandemic, the country had set an example for how to manage the virus and keep the death toll low. It was quick to put in place widespread testing and treatment and to expand the number of intensive care beds. It also had a trusted leader in Chancellor Angela Merkel, a trained scientist, whose government's social distancing guidelines were widely observed.

But today, a combination of factors has propelled a new surge, among them wintry temperatures, a slow roll-out of booster vaccines and an even more pronounced spike in infections in neighbouring eastern European nations like the Czech Republic. The fact that Germany is in a kind of political limbo as it transitions between governments has not helped.

But virus experts and pandemic experts say there is little doubt that it is the unvaccinated who are contributing most to the wave of infections burdening hospitals across the country.

"It's our low rate of vaccination; we haven't done what was necessary," said Dr Herold. She was part of a team of scientists who modelled the impact of a fourth wave and warned in early summer that with the highly contagious Delta variant, at least 85 per cent of the whole population would need to be vaccinated to avert a crisis in the healthcare system.

"We are still below 70 per cent," she said. "I don't know how we can win this race against time with the fourth wave. I fear we've already lost."

Dr Merkel, speaking at the invitation of New Zealand Prime Minister Jacinda Ardern at an Asia-Pacific business summit, said on Thursday that people who are still not vaccinated must understand they have a duty to the rest of society to protect others.

"We have to make it clear that I have the right to get vaccinated, and that is a great fortune, a huge achievement of science and technology," Dr Merkel said over a video link. "But I also have a certain obligation to contribute to protecting society."

While many of the unvaccinated are in age groups that are statistically likely to experience less severe cases of Covid-19, they can pass the virus to older people with weaker immune systems, who can then end up in intensive care even with a vaccination.

Dr Merkel, who was being interviewed by Microsoft president Brad Smith, added that the challenges of the pandemic and of climate change were similar, since they were both exponential processes whose severity was hard to recognise at the start of a growth curve.

"When you see the start of an exponential increase, you have to act immediately, and an understanding of what exponential means isn't widespread in our societies," Dr Merkel said.

"That is also why we have been so unconcerned about climate change - that also has exponential growth and we have to act at a time when it is not at all visible how the numbers will grow."

Germany's vaccination rate is far better than that of many central and eastern European countries, where the death toll from the coronavirus is soaring. In Romania, for example, only about four in 10 people have had two shots, and Covid-19 deaths have hit record levels.

Still, with about one in three Germans not yet fully vaccinated, the German vaccination rate is among the lowest in Western Europe. In Belgium, Denmark and Italy, three in four people are fully vaccinated. In Spain and Iceland, only about two in 10 have yet to get the second shot. Portugal has a vaccination rate of close to 90 per cent.

The German rate lags because of pockets of vaccine resistance that are not limited to but are especially deep in the former Communist east, where the far-right Alternative for Germany (AfD) party is strong. Mr Tino Chrupalla and Ms Alice Weidel, leaders of the AfD's parliamentary group, are both proudly unvaccinated - and both tested positive for the virus in recent weeks.

"What we are experiencing is, above all, a pandemic of the unvaccinated," Health Minister Jens Spahn said this month.

Infections have also spiked in parts of Bavaria and Baden-Wurttemberg, two wealthy southern states that are home to a noisy protest movement against measures to combat the virus, known as the "querdenker", or "contrarians".

"We have two viruses in the country," Bavarian Governor Markus Soder said in a television debate recently.

"We have the coronavirus, and we have this poison, which is being spread on a massive scale," he said, referring to misinformation about vaccines.

Mr Klaus-Peter Hanke knows about that poisonous propaganda first-hand.

He is the mayor of Pirna, a town of less than 40,000 in the eastern state of Saxony, which experienced a wave of violent protests from anti-vaxxers in the final days of the lockdown last spring.

One in three voters in the voting district that includes Pirna cast a ballot for the AfD in September's national election. And just under half of inhabitants refused to get vaccinated. They have helped to make Saxony the state with the lowest vaccination rate in Germany - and with the highest per capita number of new infections.

"The readiness to get vaccinated is low here," Mr Hanke said. "We tried to counter that with dialogue. But there is a point where you hit a wall and you just can't get any further, and one result is that it has escalated."

The Covid-19 ward at its hospital is running out of beds. There, too, almost all patients - "nine out of 10" - are unvaccinated, Mr Hanke said.

And still, several restaurants in town have signs in the window inviting everyone - not just those vaccinated or recovered from an infection, as per state rules - to come inside.

This week, the mayor set up 10 control teams of three people each - a police officer, a health official and someone from the department of public order - to roam the city's restaurants, bars and hairdressers and fine those disregarding the rules on the spot. Owners have to pay €500 (S$775) and patrons €150.

"It's pretty drastic," said Mr Hanke, who has vaccine resisters in his own circle of friends. "But we see no other way to get people to change their behaviour."

Anecdotally at least, the tough approach might be paying off. Waiting times at mobile vaccination units increased to two hours this week, Mr Hanke reported, suggesting that the threat of exclusion from much of indoor public life might be nudging more people to get a shot.

Several other German states are now working on similar regulations, introducing stricter mask mandates and, instead of a negative test, making proof of vaccination or past infection mandatory for entry to many venues.

That may no longer be enough, said Dr Sandra Ciesek, director of the Institute of Medical Virology at the University Hospital of Frankfurt and co-signatory of a paper by seven prominent scientists published last week, in which they urge politicians to speed up booster shots and consider a range of measures, including partial lockdowns for the unvaccinated or even a short-term national lockdown.

The absence of political leadership at the national level at a time when the number of new daily infections is soaring beyond 50,000 has added to the muddled approach to containing the virus.

Since her Conservative Party lost the national election in September, Dr Merkel remains only as the head of a caretaker government, while likely successor Olaf Scholz has been absorbed by difficult coalition talks with two other parties.

"Where is Angela Merkel?" Der Spiegel asked in an article this week, before asking a few paragraphs lower "Where is Scholz?"

It is a question many virus experts across the country are asking, too, concerned that a lack of political leadership is wasting valuable time - and potentially costing lives.

"There is no real centre of power and responsibility. The country is missing leadership," said Dr Michael Meyer-Hermann, head of the department of systems immunology at the Helmholtz Centre for Infection Research and a member of the council of experts that has advised Dr Merkel throughout the pandemic.

"The outgoing government no longer really reacts, and the incoming government is playing everything down," he added.

After the number of daily new Covid-19 infections hit a record high on Nov 3, reaching 33,949, German virus experts sounded the alarm. The response from Mr Scholz's future coalition partners was a statement promising that there would not be another lockdown.

"For me, it was a key moment," Dr Meyer-Hermann said. "They act like the pandemic is over at a time when the numbers are exploding."