Britain will deliberately infect healthy volunteers to speed up COVID-19 vaccine efforts

A volunteer receives a shot in a clinical trial of Moderna's potential COVID-19 vaccine.
In March, a volunteer receives a shot in a clinical trial in Massachusetts of Moderna’s potential COVID-19 vaccine.
(Ted S. Warren / Associated Press)

British researchers are preparing to infect healthy young volunteers with the coronavirus that causes COVID-19, becoming the first to announce plans to use the controversial technique to study the disease and potentially speed up development of a vaccine that could help end the pandemic.

This type of research, known as a human challenge study, is used infrequently because some consider the risk involved in infecting otherwise healthy individuals to be unethical. But researchers racing to combat COVID-19 say that the risk is warranted because such studies have the potential to quickly identify the most effective vaccines and could help control a disease that has killed more than 1.1 million people worldwide.

“Deliberately infecting volunteers with a known human pathogen is never undertaken lightly,” said Peter Openshaw, co-investigator on the study. “However, such studies are enormously informative about a disease, even one so well-studied as COVID-19.”


Human challenge studies have been previously used to develop vaccines for diseases including typhoid, cholera and malaria.

Imperial College London said Tuesday that the study, involving healthy volunteers ages 18 to 30, would be conducted in partnership with Britain’s Department for Business, Energy and Industrial Strategy; the Royal Free London NHS Foundation Trust; and hVivo, a company that has experience conducting testing. The government is preparing to invest $43.4 million in the study.

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The Imperial College partnership expects to begin work in January, with results expected by May. Before any research begins, the study must be approved by ethics committees and regulators.

Although one or more COVID-19 vaccines are likely to be approved before then, the study will still be relevant because the world may need multiple vaccines to protect different groups within the population, as well as treatments for those who continue to get sick, said Dr. Michael Jacobs, a consultant in infectious diseases at the Royal Free London NHS Foundation Trust.

“We’re going to need a whole raft of interventions in order to control this pandemic,” said Jacobs, who will take part in the research.

Tens of thousands of volunteers around the world have already signed up to participate in more traditional trials of COVID-19 vaccines. Critics of challenge studies question the need to expose healthy people to the coronavirus when the disease remains widespread and vaccine development is moving quickly.


In the first phase of the British challenge study, researchers will expose 90 paid volunteers to the coronavirus using nasal drops in an effort to determine the smallest level of exposure needed to cause COVID-19. Ultimately, the same model will be used to test the effectiveness of potential vaccines by exposing volunteers to the virus after they’ve received one of the candidate vaccines.

The research will be conducted at the Royal Free Hospital in London, which has a specially designed area to contain the disease. Volunteers will be monitored for at least a year to ensure they don’t suffer any long-term effects.

Kate Bingham, chairwoman of Britain’s Vaccine Taskforce, said the study would improve understanding of the coronavirus and help in making decisions about research.

“There is much we can learn in terms of immunity, the length of vaccine protection, and reinfection,” she said in a statement.

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Challenge studies are typically used to test vaccines against mild infections to avoid exposing volunteers to a serious illness if the vaccine doesn’t work. Although the coronavirus causes mild or moderate symptoms in most people and seems to be especially mild in young, healthy individuals, the long-term effects of the disease aren’t well understood, and there have been reports of lingering problems in the heart and other organs even in those who don’t ever feel sick.


In the U.S., the National Institutes of Health has downplayed the need for challenge studies given the speed with which potential vaccines are being developed, but it has taken preliminary steps to prepare for such research in case the approach eventually is required. Those steps include examining the ethics of a challenge study, and funding research to create lab-grown virus strains that potentially could be used.

In July, the NIH’s vaccine working group published a paper in the New England Journal of Medicine noting the risks of conducting a challenge study with a virus that so far has no good treatment and is wildly unpredictable, occasionally killing even some young, otherwise healthy people.