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A nurse prepares an experimental COVID-19 vaccine at a clinic in London on Aug. 5, 2020.Kirsty Wigglesworth/The Associated Press

Imperial College London plans to start deliberately infecting volunteers with the virus that causes COVID-19 in human challenge trials that researchers hope will speed up the development of vaccines.

The trials will be the first of their kind in the world and could begin in early January, with about 90 volunteers between the ages of 18 and 30. The British government is backing the study with £33.6-million ($57.3-million) in funding.

“Human challenge studies can increase our understanding of COVID-19 in unique ways and accelerate development of the many potential new COVID-19 treatments and vaccines,” Chris Chiu, who heads the Imperial Network for Vaccine Research, told a news conference Tuesday.

Progress on the COVID-19 vaccine: How soon will it be here? How might it work? And how will we know if it's effective? Science reporter Ivan Semeniuk will answer your questions


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Scientists have long argued that the world will need more than one COVID-19 vaccine and that the first vaccines may not be the most effective. Challenge trials can shave months off development times and allow researchers to quickly compare the effectiveness of different vaccines.

Typically during a late-stage drug trial, known as Phase 3, volunteers are inoculated with a vaccine candidate and then return to their normal lives. Researchers wait to see how many become infected through their interactions with the general public – and how severely – and compare the results with a control group, which received a placebo. The entire process can take months and often involves as many as 30,000 volunteers. There are currently 250 vaccines in development around the world, with nine in Phase 3 trials.

Human challenge trials expedite the process by infecting volunteers just a couple of weeks after they’ve been vaccinated, shortening the time needed to determine the effectiveness of the vaccine candidate. They have been used to develop vaccines for the flu, cholera, typhoid and malaria.

The Imperial College program still requires final regulatory approval. Researchers acknowledged Tuesday that there are risks. COVID-19 is not fully understood and there is no known cure. That means researchers won’t have a proven “rescue treatment” if volunteers become seriously ill.

The team has tried to address those concerns by using only healthy young adults as volunteers, as they tend to be less prone to severe forms of the illness. The volunteers will be infected with the smallest possible amount of the virus, via nose droplets, and most are expected to develop mild symptoms, if any.

Volunteers will be compensated and housed in a special facility in a London hospital for up to three weeks. They won’t be allowed to leave until they have twice tested negative for COVID-19.

Once the Imperial College program is up and running, researchers said, it could be in place for years. “We may not really know what vaccines are going to be best in this initial phase and we need to have ways of comparing vaccines head to head,” said Peter Openshaw, a professor of experimental medicine at the university.

Dr. Openshaw added that the human challenge trials will also be a powerful way “to discover things about the very earliest stages of infection, before any symptoms develop, and what it is about the individual that makes him more or less susceptible.”

Thousands of volunteers have already signed up for the trials through a U.S.-based advocacy group called 1Day Sooner. The 1Day Sooner campaign in Britain is being co-ordinated by Alastair Fraser-Urquhart, an 18-year old student who was among the first to volunteer. “The risk to young healthy people like me is comparatively so tiny that it’s ethically okay to run a challenge trial compared to the massive benefits it would bring,” Mr. Fraser-Urquhart said in a recent interview from his home in Stoke-on-Trent.

He’s also hoping that Canada and other countries follow Britain’s lead. Health Canada has yet to approve a human challenge trial.

While many scientists have welcomed plans to start human challenge trials, some said ethical concerns need to be addressed. “There are significant challenges in ensuring volunteers thoroughly understand the risks of what they are being asked to do – and the uncertainty of any benefit,” said Katharine Wright, assistant director of the Nuffield Council on Bioethics.

There have also been questions about how effective the trials will be in determining whether a vaccine works on vulnerable people, given that the Imperial College study only involves healthy young adults. Dr. Chiu said the age of volunteers could be broadened somewhat as the testing progresses.

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