Plan to accelerate the rollout of the second dose of the vaccine to the over-50s will not delay younger people being offered their first dose, England’s chief medical officer has said.

The Prime Minister announced on Friday that the over-50s will now be offered their second jab eight weeks after their first – instead of 12 weeks.

The change comes as the UK tries to ward off the possibility of a new surge in cases caused by the India variant, which is feared to be up to 50% more transmissible than the Kent variant.

Boris Johnson told a Downing Street press briefing: “The race between our vaccination programme and the virus may be about to become a great deal tighter, and it’s more important than ever therefore that people get the protection of a second dose.”

He said the Joint Committee on Vaccination and Immunisation had advised speeding up second doses to vulnerable groups.

Despite the change in tactics, Professor Chris Whitty said it was still the Government’s aim for everybody to have been offered a first dose of the vaccine by the end of July.

“The prioritisation of second doses will not, we think, delay the situation, the rollout, for people who are in younger ages,” he told the briefing.

“We hope to get all the way through to everybody having their first vaccine by the end of July – that is the aim.

“Additionally, there is an aim for people of all ages to accelerate to some degree the point at which people get their second vaccination.”

Prof Whitty added: “This is because we think those who have a second vaccine will have greater protection, not only against the original variants but also against this new variant.”

He said even with the India variant, the number of people who are testing positive for Covid-19 in the UK is “on a steady downward path and is stable” in terms of the overall numbers.

There is also a “steady decrease” in the numbers of people who are in hospital.

Prof Whitty said the number who have died following a Covid-19 test has been steadily decreasing with the most recent seven-day average standing at seven deaths a day.