Preclinical testing: Vaccines given to animals to see what response it produces.
Phase 1 Safety Trial: Scientists test the vaccine on a small number of people for safety and dosage.
Phase II Expanded Trials: Hundreds of people included in the trials. Scientist give vaccine to different groups, elderly and children, for example, to test safety and efficacy.
Phase III Efficacy Trials: Thousands included in testing of vaccine versus placebo. This trial is crucial because a vaccine must protect at least 50 percent of vaccinated people to be considered effective.
Approval: Many countries will issue emergency use authorization to combat the pandemic.
Warp Speed: The U.S. government's Operation Warp Speed will name five or more vaccine projects and give them billions of dollars.
Combined Phases: Some researchers are combining phases, testing for the first time on hundreds of people.
