Cheng told a briefing that the company would keep the “active” drug substance in stock while it awaited regulatory approval around the world.

She said there would be enough vaccine for 20 million doses in Britain by the end of the year, with enough “active” drug substance for 70 million doses for the UK by the end of Q1 2021.

She said she expected that to translate into 4 million finished vaccine doses by the end of 2020, and 40 million finished doses by the end of Q1 next year.

“If we go with a half dose you can imagine for the initial dose, we will be able to double the number of vaccinations here,” she said.

She said the figures referred to the vaccine doses being manufactured by AstraZeneca, and not those being made by manufacturing partners.

REUTERS