First Phase 3 Coronavirus Vaccine Candidate Begins Testing in US The experimental vaccine, developed by Moderna and the National Institute of Allergy and Infectious Diseases, began Phase 3 trials on Monday. Moderna CEO Stephane Bancel, via statement The trial will consist of about 30,000 adult volunteers who will be separated into a trial group and a control group, according to CNN. Moderna, along with several other drug manufacturers, have received funding for vaccine research through the federal government’s Operation Warp Speed program. The World Health Organization currently lists roughly 25 potential vaccines in clinical trials worldwide.