Cobra Biologics is one of the firms working to make a potential vaccine known as ChAdOx1 nCoV-19 being developed by scientists at the University of Oxford.
Chief Executive Peter Coleman said the firm is not responsible for proving the efficacy of the vaccine, with those trials being run by the Oxford team, and there was a lot of risk involved in the project.
But he said that if a 200-litre manufacturing run planned for the middle of May were successful, the company would be ready to produce 1 million doses a month.
"(That's) more than enough for clinical trials, but also potentially a start to stock up for commercial supply," Coleman told Reuters, adding that it could have capacity for up to two million doses in repeat batches.
"The speed at which we're operating is much quicker than it ordinarily is. And to start building up batches for commercial supply before you've even got to phase one (clinical trials) is pretty unusual."
British pharmaceutical firm AstraZeneca has joined the Oxford vaccine programme to develop, produce and distribute the potential vaccine to help make it available as soon as possible if it succeeds in clinical trials.