The chairman of the UK Vaccines Taskforce has said he is “very optimistic” of meeting the target to jab all over-50s by May.

Downing Street confirmed on Friday that the vaccine programme is intended to reach all those aged 50 and over, as well as adults aged 16-65 in an at-risk group, by May – having previously said it aimed to do so “by the spring”.

Vaccines tsar Clive Dix, speaking to BBC Radio 4’s Today programme, said: “Every time we’ve been set an objective in the taskforce, we’ve met it and we will work day and night to ensure whatever the target that is feasible can be met.

“I’m very optimistic that we will definitely meet the May target.”

Dr Dix, who took over from Kate Bingham at the end of last year, denied there was likely to be a slowdown in the rate of vaccinations when second dose jabs were also due to be administered.

“No, I’m confident that we are going to be supplying enough vaccine to roll out any type of protocol,” he added.

Dr Dix also said scientific studies taking place in the UK would help the world get “ahead of the game” on vaccine-evading new variants.

While admitting there was the “possibility” of a so-called “black swan” mutation emerging that could escape the vaccines currently on offer, he added: “The UK is properly at the forefront of surveying all of these variants.

“We have actually sequenced nearly 50% of all the virus that has been sequenced in this pandemic at the Sanger centre in Cambridge.

“Taking that data and having scientists look very seriously at what’s emerging – where the mutations are occurring, what they might do to the protein – we can kind of second guess some mutations that haven’t even occurred yet and we can go ahead and make those.

“And that’s part of the collaboration – we’ll make libraries of future vaccines, just small amounts, enough to then, if it does occur, do a quick clinical study to see that it works and then start manufacturing.”