Moderna’s (MRNA.O) COVID-19 vaccine is being reviewed on Monday by technical experts for possible WHO emergency use listing, a World Health Organization spokesman told Reuters.

“Moderna is being reviewed at the TAG (technical advisory group) meeting today,” WHO spokesman Christian Lindmeier said in reply to a query. A decision on the U.S. drugmaker’s vaccine was expected in one to four days, he said.

So far COVID-19 vaccines made by Pfizer (PFE.N), AstraZeneca (AZN.L) and Johnson & Johnson (JNJ.N) have already received WHO approval, which is a signal to national regulatory authorities on a product’s safety and efficacy.