Berlin - German vaccine manufacturer BioNTech plans to produce 2 billion doses of its jab in 2021, increasing its initial plan to produce 1.3 billion doses by more than 50 per cent, welcome news as lawmakers addressed shortages and a slow vaccine campaign roll-out.

"We are on track to scale-up our manufacturing capacities," the company announced in Mainz.

The company said conversion work at Pfizer's Puurs plant in Belgium had been successfully completed, and the drugmaker was back on schedule to deliver the promised vaccine doses to the European Union.

Pfizer and BioNTech will raise delivery volumes to ensure they can meet their contractual commitments in the first quarter - and can deliver up to 75 million more doses to the European Union in the second quarter.

Chancellor Angela Merkel defended the European approach to the procurement of the coronavirus vaccine and appealed for understanding for the pace of the roll-out.

She pointed out that production capacities in Europe were limited compared to the US, that the EU had spent a long time negotiating liability issues, and also that it had not opted for emergency approval of vaccines.

Merkel said that while pharmaceutical manufacturers knew that the government needed to plan, it was also understandable that the companies did not want to promise more than was fair in view of complex production processes.

Her videoconference was billed a "vaccine summit" and including the premiers of Germany's 16 states, as well as representatives from vaccine producers and the European Commission, which buys vaccines on behalf of EU member states from various companies.

The EU has also been forced to defend its vaccine strategy in recent weeks, particularly after logistical problems forced British-Swedish company AstraZeneca to announce that it would initially provide far fewer doses than promised of its vaccine.

EU Health Commissioner Stella Kyriakides defended the EU's approach during the online meeting, saying the bloc had negotiated the best possible deals with manufacturers.

And she echoed a commitment to vaccinate 70 per cent of the adult population by the end of the summer.

The European Commission also defended the pace of vaccinations and its procurement strategy, saying short supplies were not due to lack of money.

"With more money, we definitely would not have got more vaccine doses," Sandra Gallina, the commission's director general for health, told the European Parliament's budget Committee.

She said that the EU had secured the doses of the vaccine "extremely quickly."

Gallina also said that time had been needed to rule out risks and clarify liability issues, saying safety was paramount.

Meanwhile, other companies also committed to helping produce vaccines against Covid-19.

Vaccine production to be increased

Pharmaceuticals heavyweight Bayer is to venture into vaccine production by extending a partnership with CureVac, which plans to submit its vaccine to regulators in the coming months.

CureVac chief executive Franz-Werner Haas hopes that Bayer's involvement in manufacturing will lead to "several hundred million" doses of his company's drug being made available towards the end of 2021.

German Health Minister Jens Spahn noted that the CureVac vaccine provided long-term prospects, for example if people need booster shots later in the year.

Merkel also suggested that vaccines could be needed over a longer period of time - possibly for years to come, as with flu vaccines.

After the summit, she also acknowledged that if the virus continued to mutate, this would present further complications.