Now, the challenge

Human challenge trials involve deliberately exposing volunteers to disease to gain scientific insights. This controversial public health tool is rarely deployed, and usually only when there is an effective treatment for the disease being studied. While treatment has significantly improved since the start of the pandemic, there is still no cure for covid-19, the illness the virus causes. Still, the staggering costs of each additional day without an effective coronavirus vaccine emphasize a key advantage of challenge trials: speed.

Traditional vaccine trials commonly involve recruiting tens of thousands of volunteers, giving a placebo to one group and a vaccine to the other, and observing differences in outcomes between the two groups over the course of several months. This method is tried, tested and relatively slow. Under certain circumstances, challenge trials could hasten crucial discoveries about vaccine efficacy while using far fewer volunteers. That’s because, unlike traditional vaccine trials in which only a small fraction of volunteers would be exposed to the pathogen as they go about their lives, all participants in human challenge trials are guaranteed exposure. Thus, challenge trials could give researchers rapid feedback about what is and isn’t working — a major advantage in an ongoing global health crisis.

While challenge trials would rightfully have to clear a very high ethical bar to proceed, it’s worth noting that society routinely accepts contributions from brave individuals who step forward.