Table 2 Lessons for DMC and trialists in future pandemic (and non-pandemic) trials

• Emphasise the need for wider trust in the judgement of a properly convened and expert Independent DMC (with names of DMC members available publicly to facilitate this trust)

• Liaise with regulators at an early stage to ensure that the role of the DMC is properly understood in order to avoid later requests for unblinded interim results

• Employ factorial designs where appropriate to allow simultaneous unbiased assessments of multiple treatments as rapidly as possible

• Ensure DMC includes members with a wide range of expertise in clinical trials, statistics, epidemiology, and clinical medicine and include individuals with expertise in monitoring the safety and efficacy of treatments in any special populations (e.g. children and pregnant women)

• DMC should adhere to the principle that decisions are made by the chief investigators and steering committee unless there are either safety concerns or a definitive efficacy result

• Ideally enrol a second unblinded statistician to produce reports for the DMC to cross-check results and provide resilience in case of illness