The European Commission announced Wednesday it has reached a deal with a sixth pharmaceutical firm, this time BioNTech-Pfizer, to reserve a further 200 million doses of a potential coronavirus vaccine.

"Our chances to develop and deploy a safe and effective vaccine have never been higher, both for Europeans here at home, or for the rest of the world," European Commission president Ursula von der Leyen said.

"To defeat coronavirus anywhere, we need to defeat it everywhere."

Brussels has previously signed deals with Sanofi-GSK, Johnson & Johnson, Curevac, Moderna and with AstraZeneca to be ready to procure doses quickly if and when any of the companies develop a safe and effective coronavirus vaccine.

"We are optimistic that among these candidates there will be a safe and effective vaccine against Covid-19 to help us defeat this pandemic," the EU health commissioner, Stella Kyriakides, said.

In a statement, BioNTech said the agreement includes an option for another 100 million doses.

Deliveries could start as soon as the end of 2020, if the labs successfully clear the various tests phases.

"We have activated our supply chain, most importantly our site in Belgium, and are starting to manufacture so that our vaccine would be available as soon as possible, if our clinical trials prove successful and regulatory approval is granted" said Albert Bouria, chairman and chief executive of Pfizer.

Labs around the world are racing to produce a vaccine to help end the worst health crisis in over a century.

More than 200 candidate vaccines are currently being developed with roughly two dozen at the stage of clinical trials with human volunteers.

Countries have also been scrambling to ensure they have sufficient doses, with the world's wealthiest nations making pre-orders worth billions to secure deliveries even before the vaccines have completed tests.

Amid concern US President Donald Trump will pressure regulators to approve a vaccine ahead of the presidential election in November, the CEOs of nine companies -- including BioNTech and Pfizer -- this week pledged to "uphold the integrity of the scientific process".

Specifically, the companies said they would only seek emergency authorisations for vaccines "after demonstrating safety and efficacy through a Phase 3 clinical study that is designed and conducted to meet requirements of expert regulatory authorities such as FDA," the US Food and Drug Administration.