About 30,000 people who have never had COVID-19 will participate in Phase III testing of a vaccine. Protocol established by the Centers for Disease Control and Prevention requires any vaccine to be tested in several phases before it can be used. The stages of the testing process include exploratory testing, pre-clinical and clinical development, regulatory review, manufacturing and quality control.
Phase I involves a small number of people and initial results are evaluated. In Phase II, the vaccine is given to a larger group with specific conditions relating to an individual virus. In Phase III, the efficiency and safety of the vaccine is evaluated. CDC also has a fourth phase that allows for more formal and ongoing studies after a vaccine is approved and licensed.