The European Medicines Agency said it is reviewing Pfizer’s and BioNTech’s investigational COVID-19 vaccine using a “rolling” review process that will assess the latest study data without waiting for the companies to file a completed application.

The messenger RNA-based vaccine candidate, BNT162b2, prompts cells to make proteins mimicking the coronavirus’ outer surface, spurring the immune system to repel the virus.

BNT162b2 is currently being assessed in phase 3 studies in the U.S., Brazil, South Africa and Argentina.