I touched on the Pfizer covid19 vaccine trial during my #ACR20 CRC talk this morning. I am not an expert on vaccine trials - this is a specialized field within biostats! I highly recommend you give @nataliexdean a follow if you are interested in hearing from an expert
Here are some other references #ACR20: OARSI Clinical Trials Recommendations: Key analytic considerations in design, analysis, and reporting of randomized controlled trials in osteoarthritis https://www.sciencedirect.com/science/article/pii/S1063458415008493
Statistical lessons learned for designing cluster randomized pragmatic clinical trials https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5025337/
Adaptive designs in clinical trials: why use them, and how to run and report them https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-018-1017-7
Understanding controlled trials Crossover trials https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1113275/
Non-Inferiority Clinical Trials to Establish Effectiveness Guidance for Industry (from the fda) https://www.fda.gov/media/78504/download