Credit – Getty Images—Jonnie Miles
On Oct. 20, researchers at the Imperial College of London announced plans for the first human challenge study of COVID-19, which involves deliberately infecting volunteers with the virus that causes the disease, in order to test the effectiveness of vaccines.
The strategy is controversial, as researchers have to weigh the risks of infection against the benefits of learning how well the various vaccine candidates can fight that infection. The strongest argument in favor of the studies has to do with time. If cases of COVID-19 are waning, then the likelihood that people who are vaccinated would get exposed to and potentially infected with the virus naturally declines as well, and it takes researchers longer to accumulate enough data to tell if a vaccine is effective or not. By intentionally exposing people to the virus after they have been vaccinated, researchers can shrink this timeline significantly.
Scientists have used the model to test vaccines against a number of different diseases, including the very first one against smallpox—Edward Jenner infected his son with cowpox, and then exposed his son to smallpox as a way to test his theory that exposure to the former would protect his son from infection by the latter. Scientists tested an H1N1 influenza vaccine by exposing people to the flu, and did the same with a cholera vaccine and the bacterium that causes it. But the strategy requires a solid base of information about both the disease and the vaccine in order to justify the risks. More recently, for example, scientists considered intentionally infecting volunteers with the Zika virus to test vaccines against that disease, but ultimately decided they didn’t have enough data to justify the risk.
Adair Richards, honorary associate professor at the University of Warwick who last May published guidelines on how to ethically conduct human challenge studies, notes that during a pandemic, the risk of delays in developing treatments should be considered alongside the risks to volunteers who are intentionally exposed to disease. “There is a moral weight to inaction as well as action,” he says. “There is an unseen risk if we don’t do [these studies]. We send a lot of doctors, nurses and care workers to work every day, and some will get really sick and die of COVID-19 in the next few weeks. [Those] few weeks count—that’s the unseen risk.”
More than 38,000 people in the U.S. agree, and have registered their intention to volunteer for challenge studies on 1DaySooner.org, an online recruiting group—despite the fact that no such studies have been planned in the country yet.
The London-based scientists still need to submit a detailed proposal to regulatory agencies on how they could conduct their study. If the proposal is approved, the team won’t start exposing any volunteers until January. Before that, they will first need to determine what dose of SARS-CoV-2, the virus that causes COVID-19, is safe to give to people but can still produce