What Is an Emergency Use Authorization?

In the United States, vaccines must be approved by the Food and Drug Administration (FDA) before they can be used. The FDA bases its decision on data from clinical trials. In a clinical trial, the vaccine is given to volunteers—sometimes tens of thousands of them—while others get a placebo, meaning an injection that doesn’t contain any vaccine. Scientists observe whether the people who got the vaccine get fewer cases of the disease than those who got the placebo. This means that the vaccine appears to work in those people; this is called the vaccine’s “efficacy.” The scientists also watch out for unexpected side effects that the vaccine might have caused. This is called the vaccine’s “safety.”

If the clinical trial data shows enough evidence of efficacy and safety, the FDA will approve the vaccine and license it for use in the United States.

Sometimes, the FDA will allow a medical product that has not yet been fully approved to be used in an emergency to diagnose, treat, or prevent a serious illness. This is called “emergency use authorization” or “EUA”.

An EUA may be issued when the FDA determines that the product “may be effective” against the disease based on all the available scientific evidence. This is a lower standard than required for full approval of a product; it uses early data gathered from clinical trials.

More information on EUAs is available from the FDA website.