STUTTGART, Germany — While much of the world is aching for a coronavirus vaccine, Lilia Löffler is adamant that her three children won't be getting any jabs.

Shrugging off light rain to join a two-hour bike protest of shutdown rules, Löffler said that previously she vaccinated all her kids. But she changed her mind after what she’s been hearing at demonstrations and reading on the Internet during the pandemic. She noted that her 6-year-old son is supposed to get a shot for measles ahead of school in the fall.

“But he won’t get that,” she said. Or any other vaccination.

The possibility that Germany’s anti-vaccination movement may gain new adherents like Löffler has been a concern for health authorities, as the coronavirus unites a mishmash of groups resistant to the prospect of a vaccine, from far-right conspiracy theorists to hippie moms.

Germany already had a fervent anti-vaccine movement, reflecting a historic skepticism of government control and an affinity for alternative medicine. Now, health experts have warned that even if a coronavirus vaccine is approved, refusals could open the way to a resurgence of the virus while threatening efforts to keep other preventable diseases in check.

“With such a bad pandemic, there were people that said it would make anti-vaxxers wake up and see that vaccines are important,” said Heidi Larson, director of the London-based Vaccine Confidence Project. “But it’s actually done the opposite.”

Anti-vaccine groups have become highly “active and aggressive,” she said. “I think we are in a vulnerable spot right now.”

In Germany, conspiracy theories over a vaccine abound. Attila Hildmann, a vegan chef, has become one of the leading voices of the resistance, accusing the health minister of promoting a surveillance state and forced-vaccination program at the behest of billionaire Bill Gates.

Amid the fervor, the German government has assured the public that any coronavirus vaccine would be voluntary. “The government is accused of secretly plotting to introduce mandatory vaccination,” said spokesperson Ulrike Demmer. “There will be no obligatory vaccination against the coronavirus.”

That’s different from the approach Germany has taken with measles. To address what health officials warned was one of the worst efforts to combat measles in Europe, Germany last year made the measles vaccine mandatory for children entering preschool or kindergarten. Parents who do not follow the rules face fines of 2,500 euros, about $2,800.

Isolde Piechotowski is an infectious-disease expert with the health department in Baden-Württemberg, a southwest German state known for a particularly strong anti-vaccine community. She said her office was inundated with calls and emails after the measles announcement. Since the coronavirus pandemic began, there has been another deluge.

“The messages from these people — they suppose that there will be a mandatory vaccination. That’s the contents of a lot of emails and letters right now,” she said. “They are trying to influence those decisions, even though there is no such decision to be made right now.”

Surveys in Germany conducted by the University of Erfurt found that in late June, 64 percent of respondents said they would be willing to get a hypothetical coronavirus vaccine — down from 79 percent in mid-April. The notion of mandatory vaccination was rejected by 38 percent of respondents.

“Even with a perfectly functioning vaccine, this might not be enough for herd immunity,” said lead researcher Cornelia Betsch.

That echoes a warning for the United States by Anthony S. Fauci, the government’s top infectious-disease specialist. On Sunday, Fauci told CNN that while he’d “settle” for a vaccine that is 70 to 75 percent effective, if a third of Americans are reluctant to get vaccinated, as some opinion polls suggest, achieving herd immunity would be “unlikely.”

Germany’s vaccination rates for childhood diseases appear to be somewhat higher than those in the United States, according to comparative data compiled by the Organization for Economic Cooperation and Development. But Germany’s reported figures may overstate vaccination rates — and underestimate anti-vaccine sentiment.

German health insurer Barmer calculated that, based on its patient databases, 89 percent of 6-year-olds were adequately immunized against measles in 2017, before the measles mandate. That’s far lower than Germany’s reported measles vaccination rate of 97 percent for that year and falls short of the 95 percent target for population herd immunity.

The Robert Koch Institute (RKI), Germany’s federal agency for disease control, acknowledges that its official data reflects only what families indicate on vaccination cards at school entry and excludes those who don’t present a card. Assuming all those without cards are not fully vaccinated would mean a “worst case” rate of 81 percent, health officials said.

RKI says its data from a wider range of health insurance companies estimates full measles coverage at 93 percent at school age — still below the 95 percent target. Health authorities single out late vaccinations as a particular problem, with only 74 percent of children receiving their second measles dose in the recommended time period.

One of the hubs of Germany’s anti-vaccine movement is Baden-Württemberg, a wealthy region bordering France and Switzerland and home to auto giants Daimler and Porsche. During the peak of Germany’s shutdown protests in May, the largest crowds congregated in the regional capital of Stuttgart. More than 5,000 people marched through the streets, bolstered by a contingent of anti-vaxxers.

Those tracking growing resistance to a hypothetical vaccine say people may feel a vaccine has become less urgent since Germany managed to flatten its coronavirus curve.

But vaccine attitudes in Germany are complicated by the country’s political history, with the Third Reich leaving behind a legacy of unease over government mandates.

Resistance is also tied up with the country’s alternative and holistic medicine traditions. Samuel Hahnemann, the father of homeopathy — whose statue sits on Washington’s Scott Circle — was a German from the eastern state of Saxony. And it was in Stuttgart that Rudolf Steiner, an Austrian who devised anthroposophical medicine, opened his first Waldorf School 100 years ago.

While the Waldorf institution has distanced itself from anti-vaxxers, the Steiner philosophy is rooted in free will and independence of thought, and some of his followers are vaccine skeptics. In Baden-Württemberg, infectious-disease specialist Piechotowski said, low vaccination rates can be attributed, in part, to “quite a high number of people who are following the anthroposophic philosophy.”

“It’s become very common, in the past 20 years, to think that typical child illnesses are good for healthy development,” said Natalie Grams, formerly a practicing homeopathic doctor who now speaks out against what she sees as pseudoscience. “People are trying to avoid early vaccinations, and this comes from homeopathic and anthroposophic thinking, very much. There’s a common thought that early vaccinations harm little babies.”

Grams said she is concerned how the movement appears to have expanded in just the past few months.

“The movement is getting far more political influence,” she said. It’s no longer just 2 to 4 percent of the population against vaccines, she added. “It’s far more people. The situation is much more intense than if it was just the anti-vax movement spreading disinformation about a coronavirus vaccine.”

The government needs to build support for a coronavirus vaccine even before one exists, she added, so people wary of a hastily developed medical intervention don’t turn to conspiracy theorists or hardcore anti-vaxxers to fill the knowledge gap.

Christoph Hueck, a Waldorf educator who has spoken at shutdown protests, said he sees a chance to get his message out and doesn’t mind who is in the audience as long as he speaks his “truth.”

“The only thing is to make my point of view as clear as possible,” he said. “As spread out as possible. I don’t feel like I’m a conspiracy theorist.”

But his talking points touch on conspiracy theories involving Bill Gates, the World Health Organization and vaccine tattoos. The risk of the coronavirus is overblown, he said. He said he hopes people will start to demonstrate and take off their masks.

He said he’s not anti-vaccine but against compulsory vaccination.

“You cannot send your kid to school anymore unless they are vaccinated,” he said. “The state wants to control its citizens. This is the dictatorship of health, which sets itself above the value of freedom.”

Nadine Schmid, 37, who runs a “natural medicine” practice just outside Stuttgart, said she thought carefully about vaccines for her 3-year-old and 7-year-old. The elder child has had a measles shot, the younger only tetanus.

She said there has been tense discussion in her community since the measles vaccine became mandatory. “Corona has accelerated that debate,” she said. For a vaccine, everyone should be able to choose, she said, but it’s “not for me or my children.”

Glucroft reported from Stuttgart. Luisa Beck in Berlin contributed to this report.