Clinical trials are a type of research that studies new medical interventions and evaluates their effects on human health outcomes.
Phase 3 studies involve large groups of volunteers (from several hundred to thousands) to investigate the efficacy of an intervention as well as to monitor adverse effects, and to collect information that will allow the intervention to be used safely. Phase 3 studies are often the step right before a new intervention is approved. Participation in any phase of clinical trials is voluntary.
All COVID-19 vaccines, which received WHO Emergency Use Listing approval and/or stringent regulatory agencies’ emergency authorization, have undergone phase 3 clinical trials. Information about various COVID-19 candidate vaccines currently undergoing phase 3 clinical trials is rapidly evolving and can be found on the WHO website.