In summer 2020 there was a limited window to rapidly test COVID-19 vaccines using many volunteers for human challenge trials, and it was not used.

Judge as of 2020-10-27. True: no human challenge trial of a COVID-19 vaccine began in summer 2020, even though many volunteers (e.g. tens of thousands signed up through 1Day Sooner) had come forward, and contemporaneous sources describe summer 2020 as a period when such trials would have been feasible or useful (e.g. before conventional trials read out). Mostly true: no challenge trials ran, but the claimed 'limited window' is debatable or a detail is off. Mixed: challenge trials were partly pursued (e.g. formally approved or under way in summer 2020), or experts strongly disputed that they could have sped up vaccine testing then. Mostly false: challenge trials did start in summer 2020 but were small. False: challenge trials were carried out at scale in summer 2020.

Set before the research began.

1. E1 Expert partnership to explore and establish Human Challenge studies of COVID-19 in the UK UK Government (gov.uk) · 20 October 2020

   “If approved by regulators and the ethics committee, the studies would start in January with results expected by May 2021.”

2. E2 Scientists ponder human challenge trials for COVID-19 vaccines Fred Hutchinson Cancer Center · 18 June 2020

   “and I am afraid that currently there is just too much uncertainty about them to make an informed decision,”

3. E3 Covid-19 vaccines: Should we allow human challenge studies to infect healthy volunteers with SARS-CoV-2? BMJ · 9 November 2020

   “In the current pandemic, over 38 000 people have signalled their willingness to participate in covid-19 human challenge studies with 1Day Sooner, a non-profit organisation advocating for these volunteers.”

4. E4 Covid-19 vaccines: Should we allow human challenge studies to infect healthy volunteers with SARS-CoV-2? BMJ · 9 November 2020

   “The scientific and social value of challenge studies is inadequate, as we are likely to have one or more vaccines in hand without them.”

The evidence shows that the UK's COVID-19 challenge studies had not started by October 2020 and were planned for January 2021 if approved [E1], and that over 38,000 people had volunteered through 1Day Sooner [E3]. None of the evidence items shows whether any COVID-19 challenge trial began anywhere else in summer 2020, which the criteria require for this verdict.