In the corner of a COVID-19 ward in Sao Paulo, Brazil, a woman cleaning the mouth of an intubated patient carries an extraordinary hope for pretty much all of us. Slipping a mouthwash-soaked brush into an elderly woman's mouth, at great personal daily risk, dentist Denise Abranches has something more than courage in her veins.

Abranches was the first of an expected 5,000 Brazilian key workers in the healthcare system to receive a trial coronavirus vaccine from Oxford University and multinational drugmaker AstraZeneca, along with volunteers in the UK and South Africa.

Across the city, frontline medics like her have enrolled in a Phase 3 test of the vaccine's efficacy as they battle the pandemic, which has infected more than 2 million Brazilians. And it isn't just Oxford testing its vaccine in this vast human petri dish. Chinese firm Sinovac began trials last week in Sao Paulo, and US pharma giant Pfizer plans to do so soon, bringing a race among powers to prove their vaccine works first.

Yet while nations fret over securing access to a vaccine, the potential geopolitical implications mean nothing in this ward. "To volunteer is an act of love, to donate a little of yourself to people," said Abranches. Like many healthcare workers, she has been separated from her family for months of Brazil's pandemic, in order to avoid spreading the virus, and often failed to hold back her tears when asked about the loved ones she missed.

"The loneliness is greater of the patients who are suffering," she said, as if to check her own solitude. "Being here for the whole period, seeing patients die -- often without saying goodbye to their families -- that moved us all here. I largely wanted to help, and the vaccine trial needs people like us, at high risk of contamination."

As a dentist at Hospital Sao Paulo, her days are spent immersed in infected saliva, which puts her among the highest-risk subjects that the trial could have chosen when she was injected in late June. Many others in her ward have also enrolled in this globally vital trial.

As we tour their daily routine of life-saving procedures -- a tracheotomy and extubation in just 30 minutes -- more staff reveal they've had the jab, and endure the routine checks and testing that follow. One is going to receive the trial vaccine this week. Another is thinking about it. Their boss, Professor Flavia Machado, said she is about the thousandth recipient.

Safety procedures on the ward remain strict. They don't know yet if the vaccine works. And because it is a double blind trial, none knows whether they've had the vaccine, or a placebo.

DEVELOPING VACCINES AT 'WARP SPEED'

So it is that after five months of mitigating the suffering of one of the world's worst-hit cities, the medical workers of São Paulo are now asked to help bring hope to the rest of the world.

Scientists have toiled to create a vaccine in record time, with the Trump White House even naming its vaccine Operation Warp Speed as it sinks $1.9 billion into the Pfizer project. But after severe lockdowns reduced the virus's spread in Europe, Western researchers looked further afield for heavily infected populations in which to test the vaccine.

In Brazil, the virus is rampant. President Jair Bolsonaro has been dismissive of the threat, even though he contracted it himself. The country reported over 50,000 new Covid-19 cases on several days last week. Officials here have sought opportunity in the misfortune and allowed British, Chinese and US firms to run trials in hopes that Brazil may get faster local production of the eventual vaccine. The faster the population is immunized, the sooner the economy will be able to restart.

Sinovac's trial began last week with now a handful of recipients in the São Paulo healthcare system. Yet an unexpected side effect has emerged -- not of the vaccine but the geopolitical race for it. A small fringe of angry Brazilians have railed on social media against the "China vaccine." They're echoing the earlier rhetoric, critics say, of Brazilian president Jair Bolsonaro and the Trump administration about the "Chinese virus."

"God help me not to take the vaccine made by those who made the virus! #nothanks #chinesevaccineNO" reads one Twitter user's post in Portuguese about the Sinovac vaccine. "My friends, do not allow yourself to be GUINEA PIG of CHINESE DICTATORSHIP and Doria (expletive)," reads another, referring to Sao Paulo governor Joao Doria, with the same #chinesevaccineNO hashtag.

As a result, the Sinovac project has recommended that their contributors hide their identities. "This is the number one concern," said leading epidemiologist and head of the Sinovac trial, Dr Esper Kallas. "Some people may react oddly in these days to a volunteer who participated in a vaccine that was conceptualized in a Chinese company."

Kallas added that he does not see the vaccine alternatives as Chinese or British or American. "These are mankind vaccines," he said. "We need to have them available to fight this pandemic all over the world. And perhaps the ultimate solution is not going to be one vaccine, but a combination of them."

Only one participant in the Sinovac trial has spoken publicly so far, Stephanie Texieira Porto. A young doctor, she too has been separated from family for the past five months, and her eyes mist when she mentions her 90-year-old grandmother whom she's not seen.

She says she has only received kind words about her decision to participate in the Sinovac trial on social media, but was warned by the trial organizers that it could be different. "They told me to not expose myself too much, to try to not tell everybody how this study will be. It's very strange, all of it. I don't understand why [some people] hate China."

She is reticent to discuss the role Bolsonaro and his supporters have played in fomenting anti-Chinese rhetoric. "Our president, everything he says is important and the population believes him. He says ... that it's the flu. He's said bad things about China. I prefer not to talk about him."

If successful, the two vaccine trials already underway should bring mass-produced vaccines to Brazil faster. AstraZeneca has agreed to let Brazil's Fiocruz center make the vaccine locally, producing bulk quantities even before the trial ends, and Sinovac has agreed to share its technology with Brazilian partners. Brazil's interim health minister recently expressed interest in buying doses of the drug that Pfizer is developing, too, though it has yet to begin trialing the drug in São Paulo. The company did not return a request for comment.

For Kallas, talk of a race between nations and companies is a fruitless distraction to the global task at hand. "This is a threat to all of us and finding collectively a solution is the only way to go."

Porto agreed. World powers may "feel they are in a race, but it is a common effort so humanity go back to our lives again."