https://www.yalemedicine.org/news/what-does-eua-mean
Put simply, an emergency use authorization (EUA) is a tool the Food and Drug Administration (FDA) can use to expedite the availability of medical products, including drugs and vaccines, during a public health emergency. An EUA can only be granted when no adequate, approved, available alternatives exist, and when the known and potential benefits outweigh the potential risks. An EUA also only lasts as long as the public health emergency for which it was declared.
