MARSEILLE, France — A French microbiologist who became a controversial figure in the science world — and gained a popular cult following — for promoting dubious cures for covid-19 is set to be replaced in his high-profile position.

Didier Raoult, 69, had sought to stay on in his post as director of an infectious-disease institute in the city of Marseille, despite having reached retirement age. But the head of the city’s public hospital system said it was time to “turn the page.” When the founding members of the institute met on Friday, they agreed that Raoult could hold off on his departure until next September.

For his many critics, his exit cannot come soon enough, and they worry about the damage he could do in the next 12 months.

Raoult, who wears his silvery hair down to his shoulders, is an anti-establishment figure who nonetheless had been embraced by the French scientific establishment. In 2010, he was awarded the prestigious Grand Prix Inserm — one of the highest honors for scientists in the country.

But his reputation has taken a dramatic turn during the coronavirus pandemic.

In the spring of 2020, only a few months into the outbreak, he announced that the end of the crisis was near. Among the reasons for his optimism were hydroxychloroquine, an easily available antimalarial drug, and azithromycin, an antibiotic, which he had praised as an effective treatment against covid-19.

Fox News took note. President Donald Trump began touting the drugs as possible “game changers” and said he had started to take hydroxychloroquine himself. In a surprise visit that April, French President Emmanuel Macron even flew to Marseille to meet with the scientist.

But in May 2020, amid mounting doubt about hydroxychloroquine’s efficacy against covid-19, France banned the treatment, and the U.S. Food and Drug Administration followed by revoking emergency use authorization. Some studies have suggested that the drug additionally may be linked to a higher risk of death for some patients.

Much of the world has moved on — to focus on vaccines and other treatments. Raoult, however, has dug in. He has continued to speak out in favor of hydroxychloroquine. Meanwhile, his support for coronavirus vaccines has been lukewarm. Some of his biggest fans can now be found among the vaccine skeptics at France’s weekly protests.

Speaking to The Washington Post this past week, before his replacement was announced, Raoult cited pleas from his institute’s councils to remain in office for another year. He had previously compared the efforts to remove him from the IHU Méditerranée Infection institute to a “coup,” prompted by jealousy.

“Either you’re successful, or people like you. It’s very hard to get both,” he told The Post.

But his critics, including those who supported him until a few months ago, say he has only himself to blame for the mounting criticism he has encountered — and the contentious campaign to remove him as director.

“Raoult had a very positive impact at the start of the pandemic,” acknowledged Michèle Rubirola, the deputy mayor of Marseille who is in charge of public health. She cited his early advice to “test, detect and wear masks.” But his continued promotion of hydroxychloroquine and his mixed messaging on vaccination have been a turning point. “You have to have the humility to acknowledge that you’ve been wrong,” Rubirola said.

Concerns over Raoult’s impact extend beyond France. Hydroxychloroquine prescriptions remain at far higher levels in the United States than before the pandemic, despite warnings of serious side effects from the FDA and researchers.

When Macron visited Marseille again earlier this month, he credited Raoult as a “great scientist” but blamed him for possibly having hurt the vaccination effort. Nationally, more than 60 percent of the French population is fully vaccinated against the virus, but the rates have hovered around or below 35 percent in pockets of Marseille.

Raoult says he has generally been supportive of coronavirus vaccines — and he has encouraged nurses to get vaccinated. But in contrast to his championing of hydroxychloroquine, his remarks about the vaccines have frequently focused on aspects that are likely to raise doubts.

“I never take any position against the vaccine. Never, never, never,” he told The Post, adding that “there is no question about vaccinating people who are at risk to acquire the disease, or to transmit the disease, or to have a severe form.” But he then spent much of the remainder of his response talking about the potential risks of vaccination for younger age groups.

“Is there any risk in vaccinating people?” he asked. “The answer is yes.”

With videos and posts that similarly focus on potential downsides and unknowns, the scientist has amassed more than 800,000 followers on Twitter — more than France’s prime minister and health minister combined. In a country with a population of roughly 67 million, his institute’s YouTube videos, many featuring Raoult, have been watched more than 90 million times.

In one recent video, he discussed a surge of coronavirus cases in Iceland, a country with one of the world’s highest vaccination rates. But he didn’t discuss why hospitalizations and deaths have remained low, which Icelandic authorities view as evidence that vaccines are having their intended effect. In another video, Raoult said it was too early to say whether vaccines lower the severity of covid-19.

In the recordings, Raoult often wears his white doctor’s coat and leans back into his chair, conveying a sense of certainty, even when he talks about uncertainty.

He has defended his videos as revealing the true state of scientific knowledge about coronavirus vaccines. “Scientists who are sure of something are not scientists anymore,” he said.

Though he disputes that he has sent an anti-vaccine message, some of his supporters at one of France’s protests against health passes in Marseille last week felt differently.

“I don’t want my son to be vaccinated with an experimental vaccine,” said Stéphanie Busson, who pushed her child in a stroller while holding a handwritten sign that read, “Don’t touch Raoult.” The scientist, she said, “is very important, because there’s another solution beyond vaccines, and that’s the treatments.”

“He didn’t advocate the vaccine,” added another woman, holding a poster with a photo of Raoult and the slogan “Total Support!!!” She characterized Raoult’s stance on coronavirus vaccines as “very suspicious, because there are a lot of side effects, and the side effects are never cited by the media.”

When asked about the impact of his remarks, Raoult appeared agitated, saying, “This is why I don’t want ― in general ― to speak to journalists,” and he accused the media of spreading fear of the coronavirus, despite “so few deaths.” (More than 116,000 people have died of the virus in France, according to official statistics. At least 668,000, or 1 in 500 people, have died in the United States.)

It’s difficult to avoid Raoult in France these days. On a bus in Marseille last week, a rush-hour commuter switched between music videos and Raoult lectures on YouTube. A Parisian taxi driver cited Raoult as justification for a government conspiracy. Numerous Internet memes portray him as God, a religious leader or a magician.

Some in France’s far right see him as an ally. Last week, a demonstration organized by far-right politician Florian Philippot drew hundreds of people to Raoult’s institute in Marseille to protest his possible removal.

Anti-vaccine posters were still glued to the fence around the institute days later. On the wall of the building, just below the facade glazing that makes the institute’s exterior look like a half-shut blind, workers had unsuccessfully attempted to remove graffiti slogans that featured still-legible words: “Macron,” “Shame” and “No Pass.”

Raoult denies any political ambitions and said his French supporters come from across the political spectrum. That both Trump and populist Brazilian leader Jair Bolsonaro had taken hydroxychloroquine meant that “all the liberals everywhere in the world start to be against me,” he said. “But I don’t care.”

Many of Raoult’s colleagues disagree with his assertion that he is detached from politics. In an open letter last month, several leading French doctors condemned Raoult after he shared a conspiratorial text that implicitly called for the execution of doctors considered to be in line with government views. It followed a string of attacks by anti-vaccine activists on French vaccination centers and coronavirus testing tents over the past months.

“We are individually and collectively worried,” the signatories wrote in their open letter.

Raoult has sought to distance himself. He said he does not support a revolution, but added that he fears one may occur “because people are mad.”

On Twitter, he denounced “any threats or harassment” after unknown attackers sprayed threats on the home of a man who carries the same name as Marseille’s public university hospital network director — one of Raoult’s key critics.

But some of those involved in France’s vaccination campaign fear the damage is done, and that it may be irreversible. As Marseille’s anti-health-pass protesters marched last week, Jean-Luc Jouve was working to mitigate the fallout.

Jouve, the head of the local hospital network’s medical commission, steered his motorbike along a highway elevated above the rooftops of the city, racing toward one of France’s covid hot spots — 15 minutes by motorbike, but an entire world away from the sunbathers and yachts on the other side of town.

Officials have partially blamed Raoult’s videos for a vaccination divide that has led to a surge in new hospitalizations and deaths in Marseille, even though France’s overall number of new cases has been dropping.

At a publicly run vaccination center set up to tackle the imbalance in one of the city’s northern districts, only a few people had shown up to get a shot when Jouve arrived that day.

“A 10-minute talk by Didier Raoult on YouTube,” he said, means “entire days of door-to-door discussions or educational work that has to be done in the northern districts to convince people to come and get vaccinated.”