French drug maker Sanofi has said it will help mass produce the coronavirus vaccine developed by Pfizer/BioNTech, amid EU shortages.
Sanofi says it has struck a deal to produce 125 million doses of the vaccine by the end of the year.
Pfizer-BioNTech has cited production problems, as has AstraZeneca, which is also falling behind in its EU deal.
The EU has threatened to restrict the exports of vaccines made within the bloc to deal with the shortfall.
Sanofi's chief executive said the contract with Pfizer was a first in the pharmaceutical industry and it comes after the French firm delayed the launch of its own jab.
The Germany-based BioNTech will initially produce the vaccines at Sanofi facilities in Frankfurt, starting in July, according to a Sanofi statement.
What are the supply problems?
The EU has ordered 600 million doses of the Pfizer/BioNTech vaccine for use across its 27 member states. But the company was not able to supply the 12.5 million vaccines it promised the EU by the end of 2020, due to supply chain issues.
Pfizer said last week it was delaying shipments for the next few weeks because of work to increase capacity at its Belgian processing plant.
The EU also signed a deal with AstraZeneca in August for 300 million doses, with an option for 100 million more. But the Anglo-Swedish company is also falling behind on its supply target because of production problems.
The AstraZeneca vaccine has not yet been approved by the EU, although the European Medicines Agency (EMA) is expected to give it the green light at the end of this month.
The EU had hoped that, as soon as approval was given, delivery would start straight away, with some 80 million doses arriving in the 27 nations by March.
The head of BioNTech, U?ur ?ahin, told the German magazine Der Spiegel that its delay was caused because the EU wrongly assumed that several different vaccines would be ready at once and therefore spread its orders. He also said his company was ramping up its manufacturing capacity.
The EU is desperate to boost its stuttering vaccination programme but there is no quick fix.
Today's Sanofi-Pfizer deal doesn't help in the short term.
Germany is urging Brussels to allow members states to block exports of EU-made jabs - in order to ensure the continent gets its "fair share".
But the EU trade commissioner, Valdis Dombrovskis, suggests it's better, for now, to ask companies to provide more information about where they were sending jabs - rather than blocking them.
This row with AstraZeneca is over a vaccine that the EU is yet to approve.
That is likely to happen at the end of the week, but there are signs it may not be approved for the over 65s because of a perceived lack of efficacy testing within this age group.
The challenge for the EU is to make sure any such decision doesn't look like retaliation amid this increasingly bitter argument.
Which other vaccines is the EU buying?
The European Commission says it has reached agreements with four other pharmaceutical companies to purchase hundreds of millions of vaccines, once they pass clinical trials:
Sanofi-GSK: 300 million doses
Johnson & Johnson: 400 million doses
CureVac: 405 million doses
Moderna: 160 million doses
The Commission also concluded initial talks with another company, Novavax, for up to 200 million doses.
What about the UK?
The UK did not take part in the EU vaccine scheme although it could have done (until the end of 2020).
At the time, the government said it was opting out because it felt it wouldn't be allowed to continue its own negotiations with potential suppliers and wouldn't have a say on the price, volume and date of possible deliveries.
The UK was the first country in the world to approve the Pfizer/BioNTech vaccine (and rolled it out several weeks before the EU).
The UK has also approved the Oxford/AstraZeneca vaccine and the Moderna vaccine.