Vaccine producer Sanofi said it will use its manufacturing capabilities to make 100 million doses of a rival vaccine from Pfizer and BioNTech even as it works to push its own vaccine through clinical trials.

The announcement came as setbacks for the Pfizer/BioNTech COVID-19 treatment, and a vaccine from Europe's AstraZeneca, on availability triggered political uproar across the European Union.

The EU's 27-country immunization campaign has struggled to pick up momentum, while more infections virus strains are spreading fast and fatalities from the disease are growing again.

According to Thomas Cueni, chief of the International Federation of Vaccine Manufacturers (IFVM), 77% of the world's major vaccine producing capacity is in Europe.

France-based Sanofi will give Pfizer and BioNTech access to a production plant in Frankfurt, which will start to roll out doses this summer, the company said in a statement. "We had a slight delay on one of our experimental vaccines and decided to use that time to mobilize our manufacturing capacities to help with Pfizer's," Olivier Bogillot, who heads Sanofi's French operations, said in remarks quoted by The Irish Times.

The agreement announced Wednesday marks the first time a pharmaceutical group will work to help make a competitor's vaccine, Bogillot said.

Sanofi chief executive officer Paul Hudson announced that the company would start bottling Pfizer/BioNTech vaccines in July.

"We should be able to provide 100 million doses by end of the year, which will be destined for the EU," he said.

Sanofi is developing its own COVID-19 vaccine with GlaxoSmithKline. The company's first round of Phase 2 clinical tests found the potential vaccine gave patients 18 to 49 years old the same level of protection as those who have recovered from the disease.

Sanofi is also working on another experimental vaccine with U.S. company Translate Bio. First stage trials are set to kick off in March this year.