The United States Food and Drug Administration (FDA) normally requires clinical trial-based efficacy data for authorization of vaccines. This is usually true even in emergency situations in which a public health emergency (PHE) has been declared: for example, during the COVID-19 PHE the FDA required phase III clinical efficacy trials for authorization of SARS-CoV-2 vaccines. Phase III trials, which involve the the vaccine candidate being administered to thousands of people to test for efficacy, are the longest and costliest phase of clinical testing.

However, some have argued that the FDA need not insist on clinical trial-based efficacy data for authorization of vaccines in emergency situations — especially given that the congressional authorization for Emergency Use Authorization does not require applications to include phase III clinical data.

The purpose of this question is to understand how likely US FDA is to authorize a new vaccine on an emergency basis via an Emergency Use Authorization without phase III clinical data being in the relevant vaccine application package.