Emergency use authorisation of drugs or vaccines: What, when, how

The coronavirus pandemic has seen countries opting for emergency use authorisation of drugs and vaccines as never before. The United Arab Emirates (UAE) is the latest to allow the emergency use of the Covid-19 vaccine made by the Chinese state-owned pharmaceutical company, Sinopham, for its frontline workers.

The US Food and Drug Administration had recently allowed the emergency use of convalescent plasma therapy for Covid treatment, besides existing drugs such as Remdisivir. Several countries, including India, have frameworks for allowing such authorisations for drugs and vaccines. 

When is emergency use authorisation of drugs or vaccines allowed?

If a regulator sees a reasonable likelihood