Officials in Europe on Thursday announced that they have wrapped up exploratory discussions for 225 million COVID-19 vaccines that German biotech group CureVac will develop and supply.

CureVac said that its Advanced Purchase Agreement (APA) talks with the European Union include an option to supply 180 million additional doses, once health regulators approve the mRNA-based vaccine as a safe and effective treatment against the virus. The supply deal will have 405 million shots in total.

CureVac's experimental drug is currently undergoing first-stage tests at different research facilities in Belgium and Germany. Scientists are working to determine the most favorable dose and validate the immunological characteristics of the potential drug in humans.

So far, the British-Swedish multinational pharmaceutical group AstraZeneca is the only firm to sign a supply agreement with the European Commission. The deal includes the supply of at least 300 million shots of AstraZeneca's candidate COVID-19 vaccine, which the group is developing with Oxford University.

Johnson & Johnson is also in advanced negotiations with the European officials, and has teamed up with GlaxoSmithKline and Sanofi.

Shares of CureVac were up 16 percent and closed at $66 on Thursday following news of the German company's advanced talks with the European Union member countries.

Meanwhile, U.S. officials have finalized a supply agreement with Johnson & Johnson, GSK, Sanofi, Novavax, Moderna, and AstraZeneca for 800 million COVID-19 vaccines.

CureVac listed on the NASDAQ on August 14 and secured $213 million in funding. The company is backed by billionaire Bill Gates, founder of software giant Microsoft.

CureVac CEO Dr. Franz-Werner Haas said they are happy to support and boost the European Union's program to develop and provide quick access to a safe and effective drug against the virus.

Haas pointed out that if the vaccine proves successful, the company will be "fully committed to ensuring broad access" to their treatment.