EU chief Ursula von der Leyen said Monday she expects the bloc to receive 100 million doses of coronavirus vaccines every month from April, giving a boost to Europe's stuttering inoculation campaign.

Given higher delivery volumes promised by manufacturers, and "because more vaccines are about to be approved," von der Leyen told the Stuttgarter Nachrichten newspaper the bloc should see a big ramp up in arrivals of the jabs.

The EU will receive "in the second quarter an average of around 100 million doses a month, in total 300 million by end June," she said.

The 27-nation bloc with a population of 446 million people has received 51.5 million doses of vaccines as of February 26, according to official data posted on the EU's website.

The EU has already approved three vaccines -- BioNTech/Pfizer, AstraZeneca/Oxford and Moderna -- but its inoculation campaign has been hit by delays because of production bottlenecks.

Impatience has also grown as the pace of vaccination has lagged behind countries like Britain, Israel and the United States. 

The European Medicines Agency is to decide Thursday on whether to authorise Johnson & Johnson's single-shot vaccine.

The regulator last week began a rolling review of Russia's Sputnik V vaccine.