In the past, vaccines have been developed through a series of steps that can take many years. Now, given the urgent need for a COVID-19 vaccine, unprecedented financial investments and scientific collaborations are changing how vaccines are developed. These changes to accelerate progress do not make the system any less rigorous.
Like all vaccines, COVID-19 vaccines should go through a rigorous, multi-stage testing process, including large (phase III) trials that involve tens of thousands of people. These trials, which include people at high risk for COVID-19, are specifically designed to identify and assess any common side effects or other safety concerns. What is different this time is that some of the steps in the research and development process are happening in parallel, while still maintaining strict clinical and safety standards.
As with all vaccines developed in the past, if 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. After a COVID-19 vaccine is introduced, WHO will support work with vaccine manufacturers, health officials in each country, and other partners to monitor for any safety concerns on an ongoing basis.