It's been mentioned to me in the discussion on another question that the following proposal has been advanced (in a medical journal):

Controlled human challenge trials of SARS-CoV-2 vaccine candidates could accelerate the testing and potential rollout of efficacious vaccines. By replacing conventional Phase 3 testing of vaccine candidates, such trials may subtract many months from the licensure process, making efficacious vaccines available more quickly. Obviously, challenging volunteers with this live virus risks inducing severe disease and possibly even death. However, we argue that such studies, by accelerating vaccine evaluation, could reduce the global burden of coronavirus-related mortality and morbidity. Volunteers in such studies could autonomously authorize the risks to themselves, and their net risk could be acceptable if participants comprise healthy young adults, who are at relatively low risk of serious disease following natural infection, they have a high baseline risk of natural infection, and during the trial they receive frequent monitoring and, following any infection, the best available care.

(Perhaps even more notably, the lead author of that paper was interviewed at length in Nature on the topic. But no 3rd party reactions to the proposal were included. A somewhat skeptical reaction by a French bioethicist was published by France24 (in French).)

Have any regulatory agencies (FDA or equivalents elsewhere) reacted positively to such a proposal?

  • timeslive.co.za/sport/soccer/… Commented Apr 7, 2020 at 23:59
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    @GrahamChiu: I've read that article pretty carefully, but I don't see how it's relevant to my question. Drug trials being nowadays conducted in somewhat hush-hush manner in 3rd world countries is one thing (ans somewhat common). I don't see though where they discuss a live Covid-19 challenge for the (African) test subjects in there. (Maybe you are assuming they would do it?) Commented Apr 8, 2020 at 4:23
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    Yeah, history shows prisoners etc were used for testing. I'd imagine if you were a leader of a very poor country it might seem attractive to you rather than lose millions to the virus Commented Apr 8, 2020 at 4:30
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    However, there are trials of hydroxychloroquine amongst medical staff to see if it protects them so that's similar but refers to inadvertent exposure Commented Apr 8, 2020 at 5:22
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    There's now a website looking for volunteers: thecovidchallenge.org - presumably hoping that it would soon be allowed. I've signed up today. Commented Apr 9, 2020 at 2:16

1 Answer 1


A human challenge trial ended up happening in the UK in late 2021, though it didn't examine the effectiveness of vaccines:

The UK study of 34 individuals, aged 18–30 years, shows that such trials can be done safely, say scientists, and lays the groundwork for more in-depth studies of vaccines, antivirals and immune responses to SARS-CoV-2 infection. The results were posted1 on 1 February on the preprint server Research Square and have not been peer reviewed.

Nearly half of the participants who received a low dose of virus did not become infected, and some of those who became infected had no symptoms. Participants who did develop COVID-19 reported mild-to-moderate symptoms, including sore throats, runny noses and loss of smell and taste.

Unfortunately it doesn't seem like there's any other human challenge trials in the works.

  • Tiny study, barely meets statistical minimums. I don't think I'd put a lot of credence in it since there have been deaths associated with COVID among people in that age group and younger. And notice how much they had to pay the volunteers. Who's going to fund a larger study that has to pay participants thousands of dollars?
    – Carey Gregory
    Commented Nov 10, 2022 at 2:21
  • @CareyGregory there were hundreds of wealthy people willing to fund such a trial back in 2020, the only barrier was regulatory approval. Lookup 1DaySooner - myself and tens of thousands of others signed up to do such a trial free of charge. If I had a chance to participate in the UK challenge trial I would’ve happily done so free of charge. Commented Nov 10, 2022 at 2:39

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