Larissa Bragança Itaborahy, a physician who treats coronavirus patients, is one of tens of thousands of Brazilians who have volunteered to receive experimental vaccine candidates in clinical trials. (Courtesy of Larissa Bragança Itaborahy)

RIO DE JANEIRO — The coronavirus patient was demanding his hydrochloroquine.

For months, Brazilian President Jair Bolsonaro had been touting the antimalarial drug as a miracle cure for covid-19, despite serious scientific misgivings over its efficacy and side effects. Now his supporters were asking their doctors for it.

For Larissa Bragança Itaborahy, it was one more reminder that she wasn’t up against just one infectious disease but two: the coronavirus and misinformation.

“A two-front war,” she said.

It’s one reason the 33-year-old physician is participating in clinical trials for an experimental vaccine by the Chinese manufacturer Sinovac. It might be a chance to inoculate herself against a disease that terrified her. But it was also an opening to align herself with evidence and logic — rather than the doubts and medical falsehoods she saw proliferating across Brazil.

Brazil, ravaged by the coronavirus, becomes key testing ground for vaccine

Brazil has long been recognized as one of the vaccine-friendliest countries in the world. It has universal health care, a strong public medical system, a population that has trusted vaccines and a history of carrying out massive and logistically challenging immunization campaigns. Yellow fever, measles and other pathogens have all been brought into submission.

That record, and a relentless coronavirus outbreak that has killed more than 150,000 Brazilians and infected more than 5 million, have made Brazil an inviting testing ground in the global race for a vaccine. Four of the leading vaccine candidates are being studied in the country. That’s as many as anywhere in the world. Tens of thousands of Brazilians have received trial vaccines to ensure their safety and efficacy before they’re approved for broader use.

But Brazil’s vaunted culture of vaccination is now coming under strain. The uncertainties unleashed by the coronavirus pandemic — amplified by social media and echoed by a polarizing president who has flouted health guidelines and promoted miracle cures — has rapidly eroded trust painstakingly built over decades.

In June last year, 97 percent of Brazilians said they believed in the importance of vaccinating children, according to an international a survey by the Wellcome Global Monitor. That figure was higher than the global average of 92 percent and higher than regional neighbors. But months into the country’s coronavirus outbreak, the number of Brazilians who say they would certainly get a coronavirus vaccine has fallen to 76 percent.

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Bolsonaro, rather than rallying support for a vaccine, has undercut it.

“No one can force anyone to take a vaccine,” he has said.

Falling support for a vaccine, even as researchers plow ahead with trials, has worried scientists who say Brazil is at risk of losing faith in science at the most critical time. Many Brazilians are returning to old routines while the country is still in the full grip of the virus. It’s killing hundreds, sometimes more than 1,000, every day. Tens of thousands more fall ill.

“This is a decisive moment,” said João Henrique Rafael Junior, a researcher at the University of São Paulo. In a survey published last month, he found the number of social media posts in Brazil spreading doubt and misinformation about vaccines has nearly quadrupled since the beginning of the pandemic.

“We need to reverse the curve,” he said. “We are going through the worst health crisis in a century, and we need to employ all of our strength. The time is now. Actually, the time was yesterday.”

The pandemic is amplifying the U.S. anti-vaccine movement — and globalizing it

Many Brazilians are already primed to distrust. Few believe their politicians. Many don’t trust each other. Now that same doubt is coloring perceptions of science. Thirty-six percent of Brazilians say they have very little or no trust in scientists, Pew Research reported last month, the highest score among surveyed countries.

Natália Pasternak Taschner, a microbiologist, warned the conditions could lead to disaster.

“We are witnessing something very real,” she said. “Brazil could go from a country with a strong traditional vaccine culture to a culture like France or the United States, where the anti-vaccine sentiment is strong and people don’t trust them anymore.”

Fábio Jennings was alarmed by the fake news circulating about a coronavirus vaccine in Brazil: that it will be used to control the population; that it will alter its recipients’ DNA; that it’s made from aborted fetuses. He volunteered to receive a vaccine candidate tested by researchers at Oxford University. Afterward, he talked to anyone who would listen in the hopes his experiences would help dispel doubts.

“Getting my second dose,” the 47-year-old rheumatologist said in a Instagram post last month. “Everything is going to be fine.”

Receiving an experimental vaccine doesn’t scare him. What scares him is seeing polarization and xenophobia infect an arena that was once free of them.

“Politics doesn’t matter,” he said. “We have to put science above everything.”

Brazil ignored the warnings. Now, while other countries fret over a second coronavirus wave, it can’t get past its first

But he doesn’t know if everyone can. He points to rumors about the role of China in the pandemic. Some claim the country where the coronavirus was discovered created it in a laboratory. Eduardo Bolsonaro, a federal lawmaker and the president’s son, blamed China for the pandemic. So when people in Jennings’s life learned he had received the Oxford vaccine, he said, many were relieved: At least it wasn’t the Chinese one.

Gabriel Ravazzi, the first person to receive the Chinese vaccine in the capital of Brasilia, has heard the skepticism. “Even professors and doctors,” he said. “They said, ‘But that one doesn’t work. The one that works is the Oxford one.’ ”

He tries to explain it doesn’t matter which country creates the vaccine — the science is the same. But, really, the best way to prove it is to take it.

“It makes me frustrated,” he said. “But it’s a question of time. Once it starts working, everyone who warned about the vaccine, or said don’t take anything from China, will end up getting it, too. They won’t want to keep being at risk of getting infected. The risk is in our own house, and we know this.”

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Coronavirus: What you need to know

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