Researchers in England are deliberately exposing volunteers to the coronavirus that causes COVID-19. The aim is to accelerate the development of new vaccines and treatments.

But exposing people to a life-threatening disease without particularly effective treatment seems unnecessary, if not unethical.

Human provocation experiences differ from other COVID-19 studies in one very important respect. “The main difference is control,” says Christophe chiu, infectious disease researcher at Imperial College London and lead scientist on the challenge study.

He says that with a challenge study, you know exactly when a person has been exposed to the virus and how much of the virus they have been exposed to.

Without knowing these things, you have to wait until people are accidentally exposed to the virus.

“You will end up having to recruit a lot more people, give a lot more people your vaccine candidate, before you see a result,” Chiu said.

Indeed, it took many months and tens of thousands of volunteers to prove that the Pfizer, Moderna and Johnson & Johnson vaccines were working. A challenge study might, in theory, have been able to show this with a fraction of that number and in much less time.

But that means exposing perfectly healthy people to a dangerous virus.

Chiu says he and his colleagues are well aware of this risk, and that’s why they plan to only include certain types of people in their studies.

“We have known for over a year of a pandemic now that healthy young adults are at very low risk of contracting severe COVID,” he said.

Chiu says that in addition to involving only healthy young adults, the experiments will be conducted at the Royal Free Hospital in London, a facility with extensive experience in caring for COVID-19 patients. Volunteers will be treated at the first sign of illness, a time when therapies seem to be most effective.

But studying only young adults is one of the flaws people see in provocation studies to test the effectiveness of an experimental vaccine, for example.

“The data you get from a challenge study to find out if it’s working isn’t really going to give you the information you want,” says Seema Shah, lawyer and medical ethicist at Northwestern University Feinberg School of Medicine.

Shah says it’s important to know whether a vaccine works in the elderly, people with poor health, or people of different ethnicities. You don’t get this information from a challenge study.

“When it all started at the start of the pandemic, there was a big reason to do these provocation studies, and that was to speed up vaccine testing,” Shah said.

But now, several COVID-19 vaccines have been shown to work, so the initial momentum has passed.

Viral variants are another problem that challenge studies have to contend with. Researchers are expected to collect new baseline data, such as the minimum infectious dose for each new viral variant they want to study, a process that takes time. Still, such studies can be useful for testing vaccines in the future.

For example, if coronavirus cases become less frequent, it will take many more than 30,000 or 40,000 volunteers to say whether a new vaccine is significantly better than those currently available. And it will make it much easier to compare vaccines face to face.

“So under these circumstances, a human infection model could be very useful,” says Kanta Subbarao virologist and director of the World Health Organization’s Collaborating Center for Influenza Reference and Research in Melbourne, Australia.

But she fears that not enough is known about the risks of being exposed to SARS-CoV-2, the virus that causes COVID-19, even in healthy young adults.

“We discussed very early on whether we should even consider SARS-CoV-2, and said we wouldn’t,” Subbarao said. “But we are exploring one of the most common cold coronaviruses.”

She believes the work could provide clues to a universal coronavirus vaccine, which would prevent both COVID-19 and the common cold.

Right now, Chiu from Imperial College and her colleagues are trying to figure out the minimum amount of virus needed to make someone sick with COVID-19. After that, they can turn their attention to testing new treatments and vaccines.

Copyright 2021 NPR. To learn more, visit https://www.npr.org.

MARY LOUISE KELLY, HOST:

A controversial experiment has just started in England. Researchers are deliberately exposing volunteers to the coronavirus that causes COVID-19. The aim is to accelerate the development of new vaccines and treatments. But as NPR science correspondent Joe Palca reports, some wonder if the benefits of these so-called human defiant experiments are worth the risks.

JOE PALCA, BYLINE: Experiences of human challenge differ from other studies on COVID-19 in a crucial way.

CHRISTOPHER CHIU: The main difference is control.

PALCA: Christopher Chiu is an infectious disease researcher at Imperial College London. He says that with a challenge study, you know exactly when a person has been exposed to the virus and how much of the virus they have been exposed to. Without knowing these things, you have to wait until people are accidentally exposed to the virus.

CHIU: You will end up having to breed a lot more people, give a lot more people your vaccine candidate before you can even hope to see results.

PALCA: Indeed, it took many months and tens of thousands of volunteers to show the current harvest of vaccines. A challenge study could in theory have made this much easier and faster, but it does mean exposing perfectly healthy people to life-threatening disease. Chris Chiu says he and his colleagues are well aware of this. That is why they plan to include only certain types of people in their studies.

CHIU: We’ve known for over a year of a pandemic now that healthy young adults are at very low risk of contracting severe COVID.

PALCA: Chiu says that in addition to using only healthy young adults, the experiments will be conducted at a hospital with extensive experience in caring for COVID-19 patients. But studying only young adults is one of the flaws that people see in provocation studies to test the effectiveness of a vaccine, for example.

SEEMA SHAH: The data you get from a challenge study to see if it’s working isn’t really going to give you the kind of information you want.

PALCA: Seema Shah is a lawyer and medical ethicist at Northwestern University Feinberg School of Medicine. Shah says it’s important to know whether a vaccine works in the elderly, people with poor health, or people of different ethnicities. You don’t get that from a challenge study.

SHAH: When it all started at the start of the pandemic, there was a big reason to do these provocation studies, and that was to speed up vaccine testing.

PALCA: But now, several COVID-19 vaccines have been proven to work. Still, such studies can be useful for testing vaccines in the future. For example, if coronavirus cases become less frequent, it will take many more than 30 or 40,000 volunteers to say whether a new vaccine is significantly better than those currently available. And challenge studies should make direct comparison of vaccines much easier.

KANTA SUBBARAO: So under these circumstances, a human infection model could be very useful.

PALCA: Kanta Subbarao is a virologist and director of the World Health Organization’s Influenza Research Laboratory in Melbourne, Australia. But she fears that not enough is known about the risks of exposure to SARS-coronavirus-2, the virus that causes COVID-19, even for healthy young adults.

SUBBARAO: Now we discussed very early on whether we should even consider SARS-coronavirus-2 and said we wouldn’t. But we are exploring the possibility of some of the common cold coronaviruses.

PALCA: She thinks it could provide clues to a universal coronavirus vaccine, a vaccine that would prevent both COVID-19 and the common cold. Right now, Christopher Chiu and his colleagues are trying to figure out the minimum amount of virus needed to make someone sick with COVID-19. After that, they can turn their attention to testing new treatments and vaccines.

Joe Palca, NPR News.

(SOUNDBITE OF THE KNIFE SONG, “HEARTBEATS”) Transcription provided by NPR, Copyright NPR.



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