Britain to infect healthy volunteers with coronavirus in vaccine challenge trials

London: British scientists say they will launch the world's first human challenge trials for COVID-19, in which healthy volunteers will be deliberately infected with the coronavirus, in the hope of further speeding the way to a vaccine.

The research, led by scientists at Imperial College London and paid for by the British government, is a gutsy gambit, given that people will be submitting themselves to a deadly virus with no surefire treatment.

Senior Clinical Research Nurse Ajithkumar Sukumaran prepares a COVID-19 vaccine to administer to a volunteer at a clinic in London in August.Credit:AP

The United States is moving more cautiously, with leading government researchers saying human challenge trials might be too risky or unnecessary. But the British scientists say the potential payoff is massive – that accelerating vaccine development by even three months could save hundreds of thousands of lives globally.

The British experiment is scheduled to begin in January. Volunteers will be given a laboratory-grown strain of the live virus while quarantined in a secure unit at the Royal Free Hospital in London, where they will undergo daily, even hourly, tests.

The initial phase of the study, involving 50 to 90 healthy young adults, between ages 18 and 30, will seek to determine the minimal amount of virus necessary to cause an active, measurable infection.

Next year, the scientists hope to enlist more volunteers, who will be inoculated with promising vaccines and then exposed to the virus to see how well the vaccines protect them.

Andrew Catchpole, chief science officer for hVIVO, a commercial pharmaceutical company that will recruit the volunteers, manufacture the challenge strain of the virus and conduct the tests, said the human challenge study will be reviewed by a specially convened ethics committee and Britain's Medicines and Healthcare products Regulatory Agency, its version of the US Food and Drug Administration.

Catchpole said it is not yet known which vaccines may be tested. He said possible candidates include those vaccines that have proven themselves in large-scale Phase 3 trials or they may be earlier in their development but potentially more effective.

Hedging its bets, the British government has signed an agreement for 100 million doses of a vaccine being trialled by Oxford University and AstraZeneca, as well as inking deals with Pfizer, Sanofi and Valneva.

The safety data gained from large, Phase 3 trials will still be essential to show the vaccines are ready to be deployed in large populations. But the British government hopes challenge trials will help accelerate the study of vaccines in mid-stages of development.

Catchpole said the major advantage is "you get efficacy data so much sooner" than trials that rely on chance exposure. If there is not much virus circulating in a population, it could take months and tens of thousands of inoculations to prove efficacy.

Challenge experiments have a long history in biomedical research, dating to Edward Jenner's development of a smallpox vaccine in 1796. In the modern era, challenge trials have been used extensively to study and find treatments for influenza, malaria, typhoid, dengue fever and cholera.

COVID-19, though, is different. Without a medication to reliably "rescue" volunteers from the disease, many scientists are hesitant to infect people.

Although physicians have more treatments for hospitalised patients than they did at the beginning of the coronavirus pandemic, there isn't yet an approved drug to stop recently infected people from developing a severe case of COVID-19.

The challenge trial participants will be given the antiviral drug remdesivir, which US President Donald Trump took when hospitalised this month for COVID-19 and which has been approved or authorised for temporary use to treat COVID-19 in more than 50 countries. The World Health Organisation, however, recently reported that in large clinical trials in 30 countries, remdesivir had no substantial effect on mortality. That study has not yet been peer-reviewed.

There's also growing evidence that some people develop long-lasting complications from COVID-19. Yet there's not much known about how to predict who will go on to be a COVID-19 "long-hauler" or how permanent those symptoms are.

"Young people are not immune from that outcome," Francis Collins, director of the National Institutes of Health, told The Washington Post last week. "Is it actually justifiable to intentionally infect anybody – no matter their current health status? I think that's a very open question, ethically."

One immunologist said “deliberately infecting volunteers with a known human pathogen is never undertaken lightly”.Credit:AP

Dominic Wilkinson, a professor of medical ethics at the University of Oxford, noted that volunteers would be increasing their risk but not starting from zero – they would be exposed to a strain of the novel coronavirus already circulating widely in Britain, especially among young people.

"What is the risk of trial versus the risk of living in London or going to university?" he asked.

With that in mind, he said, the need for human challenge trials is clear.

"You might get a vaccine or you might learn which vaccine is most efficient," he said, at a time when thousands are dying around the world every day. The worldwide coronavirus death toll has passed 1,100,000.

In the United States, the government has been funding researchers at Colorado State University to develop a potential challenge strain of the coronavirus that could be used if such experiments become necessary.

Creating a challenge strain takes several months, and with several large US vaccine trials projected to reach a decisive milestone that will show whether the vaccines are working by the end of this year or early next year, many scientists said the resource isn't likely to be needed.

"My own view is the need for this seems even less likely than it did a few months ago," said NIH's Collins. "The idea of needing to prepare for that was to face the possibility the viral pandemic might actually fade away and there wouldn't be enough disease spreading in the community."

The Washington Post

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