The Covid booster programme is not following the pace of the vaccine rollout, with three in five older adults yet to come forward.
Sir David King, the government’s former chief scientific adviser, said the dangers of waning immunity going into winter were clear with cases rising towards 40,000 per day.
“I think the booster scheme has been rolled out extremely slowly,” he told Sky News.
“It’s very surprising given the success of the vaccination scheme which was conducted through the NHS in an amazing, professional way.
“I’ve had my booster but I do know many older people who have not yet had their booster and I cannot understand this. If the vaccines are available, what’s happening to the rollout?”
Two in five eligible adults, aged 50 and over, have come forward for their extra jab along with more than a third of eligible health and care workers, figures show.
It means millions of those eligible are still yet to respond to NHS invites sent by text, email and letter.
Professor Neil Ferguson, of Imperial College London, said it is “critical we accelerate the booster programme” urging that the top up jabs are “absolutely” the answer to fading immunity.
He told BBC Radio 4 Today: “There’s data coming through now... which shows that if you’ve had the third booster dose of the vaccine, then you get very high loads, better than even you had after the second dose.”
Prof Ferguson also highlighted how infection rates are currently highest in teenagers while most other European countries are ahead of us in vaccinating teens and giving them two doses instead of just one.
“Two doses really are needed to block infection and prevent transmission,” he added.
“I don’t think it’s a reason to panic right now but I would certainly like to see vaccination booster doses accelerated, vaccination for teenagers accelerated,” he added.
The NHS said almost four million people have received their booster since the rollout began, more than double the rate of the initial rollout in December.
A spokesperson continued: “While the NHS can only invite people to get their booster six months on from their second jab, millions of people are getting invited within days of becoming eligible.
“There is plenty of capacity available, the NHS message remains that when you are invited, you should book in immediately.”
Who is eligible for a Covid booster vaccine?
Booster vaccine doses are available on the NHS for people most at risk from Covid, who received their second vaccine dose at least six months ago.
This includes people aged 50 and over, those living and working in care homes, frontline health and social care workers, people aged 16 and over with high risk health conditions or caring for somebody at high risk.