French-Austrian vaccine developer Valneva Wednesday announced that it had launched a Phase-3 trial of its candidate vaccine against the coronavirus -- the last testing stage before seeking regulatory approval to introduce into the market.

The study, which has been dubbed "Cov-Compare", will compare how trial participants' immune systems respond to the "VLA2001" vaccine with how they respond to AstraZeneca's jab.

Valneva announced, "Approximately 4,000 participants will receive two doses of either vaccine," noting that trials are being carried out at roughly 25 sites in the UK.

The main objective of the study is to show the superiority of VLA2001 compared to the AstraZeneca shot two weeks after vaccination, in terms of the level of antibodies that fight the virus, the company added.

If the results of the trial are positive, "Valneva aims to make regulatory submissions for initial approval in the autumn of 2021."

Unlike most high-profile coronavirus shots, which use various methods to prime the immune system to fight the coronavirus, Valneva's version is based on an "inactivated" version of the coronavirus itself.

Earlier Wednesday, Valneva said it would "deprioritize" centralized talks with the European Commission to supply its coronavirus shot across the EU's 27 member states, switching instead to "a country by country basis".

The Chief executive of Valneva, Thomas Lingelbach, complained of a lack of "meaningful progress" in talks with the European Commission.

The company said it would instead focus on both "those European Union member states and interested parties outside the EU" that expressed interest.