U.S. military physician Walter Reed and his medical colleagues famously had mosquitoes bite volunteers in order to establish that the disease was in fact borne by the flying pests. This finding was the basis of successful mosquito control efforts to reduce the incidence of the disease in tropical areas. The volunteers in these experiments were paid $200 to participate and $500 if they contracted yellow fever. These substantial payments, made in gold, would amount to approximately $8,000 and $20,000 respectively in today's dollars.

Now Rutgers University bioethicist Nir Eyal and his colleagues are proposing something like Reed's "human challenge" study as a way to speed up the development of a vaccine against the novel coronavirus that is responsible for the ongoing COVID-19 pandemic. The idea is that vaccine developers can cut more directly to what is essentially a phase three clinical trial. In phase three, vaccines already tested for safety are generally given to a large group of folks who are at risk of the targeted infection and monitored for a considerable period of time to see how many of the vaccinated people actually come down with the disease versus a group of unvaccinated people.

As Eyal explains in Nature, the proposed idea would "gather a group of people at low risk from any exposure—young and relatively healthy individuals—and ensure that they are not already infected. You give them either the vaccine candidate or a placebo and wait for enough time for an immune response. And then you expose them to the virus." So instead of waiting around for the virus to find (vaccinated and unvaccinated) folks in the wild as researchers do in regular phase three trials, you speed things up by bringing the virus to them.

Setting aside the misery of illness, according to data published in Science on July 8, the infection fatality rate for 40–49-year-olds from COVID-19 is around 1 in 2,000. For 30–39-year-olds, the risk of death drops to 1 in 5,000, and for 20–29-year-olds, the risk of death is around 1 in 14,000.* Eyal argues that such a trial would be ethical on the grounds that we allow people to engage in risky activities all of the time such as volunteering for emergency medical services that increase their risks of exposure. In addition, volunteers in the trial who are being carefully monitored for the disease would likely be safer than folks relying on the general health care system to treat them.

The authors argue that such human challenge studies, by accelerating vaccine evaluation, could reduce the global burden of coronavirus-related mortality and morbidity. If both test subjects and researchers volunteer to take this on, let's do it.

*Update: The data originally cited was an estimate from earlier in the pandemic.