The novel coronavirus is inflicting global suffering that is likely to persist until scientists produce an effective vaccine. With so much hinging on a vaccine, some are calling for a little-known epidemiological tool to speed testing: human challenge trials. Under certain conditions, human challenge trials — in which individuals volunteer to be deliberately exposed to a pathogen — could hasten vaccine development by giving scientists rapid feedback about what is and is not working. Given the pandemic’s mounting destruction, proposals that could set the world on a path to recovery sooner — even risky proposals — should be considered.

Conventionally, after a vaccine is shown to be safe in humans, thousands of volunteers are divided into two groups: Half get the vaccine, half get a placebo. As volunteers go about their lives for months, some fraction of both groups will be exposed to the pathogen. Researchers compare groups to see whether fewer of those who were vaccinated got sick. With challenge trials, instead of waiting for months and hoping enough participants are exposed — which could be tricky under social distancing orders — young, healthy people agree to be exposed to the pathogen and then are observed, providing much faster evidence of a vaccine’s effectiveness. Because challenge trials guarantee exposure to the pathogen, they also could provide useful information with many fewer participants.

Of course, a host of considerations would need to govern the use of human challenge trials, some of which the World Health Organization and the National Institutes of Health recently outlined. You would need robust procedures to inform volunteers of the risks, perhaps analogous to the one thousands of Americans go through annually when they volunteer to donate a kidney. The risks of mortality for a young, healthy person who contracts the coronavirus appear to be roughly the same as those associated with kidney donation, though there’s plenty we still do not know about long-term implications of the coronavirus. Still, tens of thousands of people from 140 countries have indicated preliminary interest in volunteering for challenge trials.

Ultimately, the wisdom of using human challenge trials to speed vaccine development will depend on a series of risk calculations, many of which remain shrouded in uncertainty. It’s possible that a vaccine currently in late testing stages will prove effective, in which case, any gains in speed from using challenge trials may not be worth the risks. However, vaccine trials have high failure rates — in a nightmare scenario, an effective vaccine could still be years away. The risks of deploying challenge trials may well end up outweighing the benefits, but with so much uncertainty — and the devastation that will persist until a vaccine arrives — it makes sense to build the regulatory, medical and ethical infrastructure to support challenge trials now, regardless of whether we feel confident we will use them.

— The Washington Post