Sanofi agreed to produce millions of doses of BioNTech SE and Pfizer Inc.’s coronavirus vaccine in an unusual collaboration to speed vaccination efforts.

The French drugmaker will give BioNTech access to a production facility in Frankfurt, which will start to deliver doses this summer, Sanofi said in a statement Wednesday. The deal will produce more than 125 million doses of the messenger RNA vaccine for the European Union.

Sanofi’s own effort to develop a vaccine with another big pharma firm, GlaxoSmithKline Plc, stumbled in clinical tests, meaning it won’t be ready by summer as expected. The production agreement allows the region to make up for some of the loss, accelerating the complex process of packaging and distributing a vaccine that needs to be kept at ultra-cold temperatures.

Pfizer and BioNTech have been looking for ways to increase the supply of their immunization, from expanding existing plants to adding suppliers and contract manufacturers.

Sanofi said that its own COVID-19 vaccine candidate will start another intermediate clinical trial in February, with the potential to reach the market in the fourth quarter. The experimental product was dealt a blow in December after a study showed it had failed to produce a strong enough response in older people, perhaps because of a formulation error.

Sanofi also plans to start early clinical trials for its own messenger RNA vaccine candidate in February or March. The stock showed little change in early Paris trading.