Vaccine manufacturer BioNTech-Pfizer is trying to ramp up production to fill the gap provided by a lack of other drugs to fight coronavirus.
Ugur Sahin, co-founder or BioNTech, said they needed to boost manufacturing capabilities but it was not a simple cases of finding new production lines.
The German biotech start-up has led the vaccine race but its shot has been slow to arrive in the European Union because of relatively late approval from the bloc's health regulator and the small size of the order placed by Brussels.
The United States ordered 600 million doses of the BioNTech/Pfizer shot in July, while the EU waited until November to place an order half that size.
Professor Sahin warned there would be gaps in supply until other vaccines were rolled out.
"We are lacking other approved vaccines and we have to fill this gap with our vaccine," he said.
"We are trying to find new co-operation partners to produce for us. But it's not as if there were specialised unused factories lying around across the world that could produce vaccines of the required quality from one day to the next.
"You can't just switch over, from producing vaccines instead of aspirin or cough syrup. The process requires years of expertise and the appropriate structural and technological equipment," he added.
The delays in rolling out the home-grown vaccine have caused consternation in Germany, where some regions had to halt vaccinations within days of starting an inoculation drive.
"At the moment it doesn't look good – a hole is appearing because there's a lack of other approved vaccines and we have to fill the gap with our own vaccine," Prof Sahin said.
BioNTech hopes to launch a new production line in Marburg, Germany, before schedule in February, with the potential to produce 250 million doses in the first half of 2021, Prof Sahin said.
Talks are also taking place with contract manufacturers and there should be greater clarity by the end of January, he added.
Health Minister Jens Spahn said on Twitter that German authorities would do everything possible to enable a swift start in Marburg.
The federal government, which has backed BioNTech with 375 million euros ($458 million) in funding, has resisted calls from opposition leaders to speed production of its vaccine by issuing compulsory licences to other drugmakers.
Another vaccine from Moderna is expected to be cleared by the European Medicines Agency (EMA) on January 6.
Mr Spahn has also urged the EMA to quickly approve the Oxford University-AstraZeneca shot cleared by Britain. The EU timeline for that treatment remains uncertain.
That vaccine was approved by India's drug regulator on Friday for emergency use, two sources with knowledge of the matter told Reuters.
