The clinical trial -- VLA2001-201 -- included 153 healthy adults ages 18 to 55 years and evaluated three different dose levels of VLA2001 based on a schedule of two doses injected three weeks apart. VLA2001 was deemed to be generally safe and well-tolerated.

What's more, it was found to be highly immunogenic; more than 90% of all study participants developed significant levels of antibodies to the SARS-CoV-2 virus spike protein across all dose groups tested, according to the company. Based on the study results, Valneva said it plans to initiate a pivotal, comparative immunogenicity phase III trial by the end of April for the high-dose level of VLA2001, subject to regulatory approval.

Valneva noted that it now believes that the timeline for delivery of 60 million doses of vaccine to the U.K. government will extend into the first quarter of 2022. Antigen sparing options are also being investigated for booster strategies based on the phase I/II data.

The aim now is to complete a regulatory licensure submission for VLA2001 to the Medicines and Healthcare products Regulatory Agency (MHRA) in the U.K. in the autumn, according to the firm. Discussions with other regulatory bodies are ongoing, Valneva said.