Operation Warp Speed was a federal effort that supported multiple COVID-19 vaccine candidates to speed up development. We analyzed the program's vaccine candidates and found that their development followed traditional practices, with some adaptations. For example, some clinical trial phases overlapped with each other and with animal studies to accelerate development. Two vaccines were authorized for emergency use—our tracker shows all the candidates. We also found that agencies are working to help mitigate vaccine manufacturing challenges. For example, agencies have taken steps to require contractors to prioritize vaccine production supplies.