The European Commission said on Wednesday it had sealed a deal with Pfizer and BioNTech for the supply of up to 300 million doses of their Covid-19 vaccine candidate.

The move follows Pfizer’s announcement on Monday that its experimental vaccine developed with BioNTech was more than 90% effective, making them the first drugmakers to show successful interim data from a large-scale clinical trial of a coronavirus vaccine.

Under the EU deal, the 27 EU countries could buy 200 million doses and have an option to purchase another 100 million.

The EU has already signed supply deals with AstraZeneca, Sanofi, and Johnson & Johnson for their experimental Covid-19 shots, and is talking with Moderna, CureVac, and Novavax to secure their vaccines.