COVID-19 vaccines go through a rigorous, multi-stage testing process, including large trials that involve tens of thousands of people. These trials, which include people at high risk for COVID-19, are specifically designed to identify any common side effects or other safety concerns.
Once a clinical trial shows that a COVID-19 vaccine is safe and effective, a series of independent reviews of the efficacy and safety evidence is required, including regulatory review and approval in the country where the vaccine is manufactured, before WHO considers a vaccine product for prequalification.
An external panel of experts convened by WHO analyzes the results from clinical trials, along with evidence on the disease, age groups affected, risk factors for disease, and other information. The panel recommends whether and how the vaccines should be used.