Update from Vox's Future Perfect: UK challenge trial will infect volunteers with Covid-19 to test vaccines.

a human challenge trial... is set to kick off in the UK within a month, now that an ethics board has given it the necessary approval. Scientists have run such trials in the past for influenza, malaria, typhoid, dengue, and cholera, but this will be the world’s first for Covid-19.

Only healthy volunteers aged 18 to 30 will be allowed to participate. The challenge trial is not meant to replace conventional clinical trials that are still ongoing for the different vaccines in development — the different types of trials will proceed along parallel tracks.

Many young people clamored to participate in the challenge trial. The advocacy group 1DaySooner gathered the names of nearly 39,000 people in 166 countries who said they’d be interested in volunteering.

The UK trial will begin with an initial phase that isn’t about testing vaccines at all; it’s about answering a preliminary question that lays the groundwork for testing vaccines later. The question is: How much of the virus does someone need to be exposed to in order to launch an infection?

Scientists will expose a small group of unvaccinated volunteers (somewhere between 50 and 90 people) to a very low dose of the virus, gradually increasing it until they find “the Goldilocks dose” — enough to infect most participants, but not enough to make them very ill.

the philosopher and MacArthur “genius grant” winner Rebecca Goldstein said signing onto 1DaySooner’s letter in support of challenge trials was “almost a no-brainer” for her.

“I have more faith both in people’s ability to understand the consequences of things, and in some people’s incredible sense of responsibility to others,” she told me last October. “Maybe it’s hard to imagine that there really are altruistic people, and we think, ‘Oh, they just don’t understand that harm could come to them.’ But I do believe there are such people.”