"Discussion with the companies has been quite constructive but it looks like there are more data that need to be submitted to us before we can progress with the different rolling reviews," the European Medicines Agency's (EMA) head vaccines strategy, Marco Cavaleri, told a news briefing.
He added EMA would continue to review data on German biotech firm CureVac's shot over the next few weeks before a conclusion can be drawn.
Cavaleri said the European medicines watchdog was expecting to soon receive data from dug makers on the effectiveness of COVID-19 vaccines on children below 12.
Cavaleri said the EMA was currently evaluating data on a booster dose for Pfizer/BioNTech's COVID-19 vaccine, to be given six months after the second dose in people 16 years of age and older.
He said other manufacturers would soon submit application on booster shots as well.
Cavaleri confirmed that U.S.-based Moderna had also asked the EMA for conditional approval of a booster shot of its coronavirus vaccine at a 50 microgram dose.
Last week, the European Centre for Disease Prevention and Control said there was no urgent need for booster doses of COVID-19 vaccines for the fully vaccinated.