This paper describes the UK Research Ethics Committee’s (REC) preparations and review of the global first SARS-CoV-2 human infection challenge studies. To frame our review, we used the WHO guidance and our UK Health Research Authority ethical review framework. The WHO criteria covered most issues we were concerned about, but we would recommend one further criterion directing RECs to consider alternative research designs. Could research questions be equally well answered by less intrusive studies? The committee met virtually, ensuring broad representation (...) across the UK nations and also ensuring applicants could attend easily. We worked in collaboration with the applicants but while we recognise that such proximity might raise the accusation of ‘collusion’, we made every effort to maintain ‘moral distance’ and all decisions were made by the committee alone. Prior existing processes and policy facilitated training and review but even with this preparation, review took time and this could have hindered a rapid response to the emergency. Review for the various follow-on studies will now be speedier and once the pandemic has subsided, our group could be reconvened in future emergencies. In conclusion, we have tried to make decisions in good faith. We know there is controversy and disagreement and reasonable people may feel we have made the wrong decision. A more detailed analysis, built on the WHO guidance, is provided in online supplemental material. (shrink)