Doctor giving a Covid-19 vaccine

The UK study plans to infect volunteers with the coronavirus in January

By Michael Le Page

Human challenge studies could help test Covid-19 vaccines

Zoranm / Getty Images

Researchers in the UK have announced plans to infect volunteers with the coronavirus from January. The initial goal will be to establish the minimum dose of infection before testing potential vaccines. The study is funded by the UK government but has yet to receive final ethical approval.

"Participant safety is a top priority," says Chris Chiu of Imperial College London, whose team will conduct the study. "We spent many months thinking about the evidence and weighing the pros and cons."

The coronavirus doses are created from a company called hVIVO because research requires a pure, quantifiable source of the virus, not an infection that spreads from person to person. The cans contain the same strain that is currently circulating and is not weakened or weakened in any way.


Volunteers will have the virus delivered to the nose in droplets, a method that has been widely used in previous studies of this type. As soon as they show signs of infection, they will be given the antiviral drug remdesivir.

A large study recently found that remdesivir did not lower the death rate from covid-19. However, seriously ill people who had already been hospitalized were involved in this process, says Chiu. He believes that giving the drug very early will stop the infection from spreading to the lungs. The team will also consider using other drugs, such as antibodies, as more evidence becomes available.

The volunteers are healthy people between the ages of 18 and 30. Initially, they are likely to be of white ethnic background, as evidence has shown that black, Asian, and ethnic minorities are more likely to get seriously ill. However, the team says it will involve volunteers from different backgrounds as soon as it is safe to do so.

The study is being carried out at the Royal Free Hospital in London. If volunteers become seriously ill, the study will be paused to see if it is safe to continue. However, the team expects most of the volunteers not even to develop symptoms.

Even in the absence of adverse events, this first phase could still take a few months if the starting doses prove to be too low, says Chiu. This is because there are only a limited number of beds available and volunteers must be quarantined for weeks even if they do not become infected.

This means it could be many months before the team can test potential vaccines by trying to infect volunteers who have been given a vaccine – called human challenge studies. At this point, one or more vaccines may already be available through conventional testing. "We'll probably see the results of Phase III studies in the next few months," says Peter Openshaw of Imperial College London.

However, many different vaccines will be developed over the next three or four years, Openshaw says, and the ability to conduct trials with human challenges will be a very valuable way to compare them.

"This will be a way to compare the effectiveness and safety of vaccines much faster," says Robert Read of the University of Southampton, UK.

Challenge studies of this type don't show whether vaccines protect the oldest and most at risk, but they can accelerate progress by showing which potential vaccines have no chance of working, says Andrew Catchpole, chief scientist at hVIVO. "What it can do is get quick vaccines for these groups," he says.

The team will set up a website where people can register their interest in participating while the study has yet to be approved by the UK Medicines and Health Products Regulatory Authority and the Health Research Authority. Volunteers are compensated for their time, but Chiu declined to say how much money they will receive.

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