Health secretary Sajid Javid has encouraged anyone who hasn't had their vaccine or booster jab to make an appointment.
He made the plea during a Downing Street press conference on Wednesday.
When discussing COVID-19 variants, Javid said: “We need to be ready for what lies around the corner. This means our ongoing programme of booster jabs is so important.”
Millions of people who are eligible for their third jab are yet to have it.
Javid warned the coronavirus pandemic is “not over” and said cases could rise to 100,000 a day.
He said hospital admissions are now approaching 1,000 per day and deaths are “still sadly over 100 a day”.
Javid added: “We’ll do what it takes to make sure that this pressure doesn’t become unsustainable and that we don’t allow the NHS to become overwhelmed.”
He said: “This pandemic is not over. Thanks to the vaccination programme, yes the link between cases and hospitalisations and deaths has significantly weakened, but it’s not broken.”
Business secretary Kwasi Kwarteng said on Wednesday morning that the slow uptake of coronavirus booster jabs is “something that we really need to address”.
He told Sky News the vaccine rollout had been “the most successful thing we’ve done” but urged those eligible to take up the offer of a third dose of the vaccine.
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He said the government was “concerned” about rising deaths, but added that “it’s something we’re going to have to live with”.
Meanwhile, England’s chief medical officer professor Chris Whitty urged people to get vaccinated or take up the offer of a booster shot.
How many people have had a COVID booster?
The latest NHS England figures show that 3,846,287 booster doses have been administered in England as of 19 October, with 1,298,493 of those being given to people over 80.
The NHS said last week that only two in five people aged 50 and over who are eligible have forward for their extra jab.
It is estimated that around 8.5 million people are currently eligible for the jab in England, according to calculations by John Roberts, from the COVID-19 Actuaries Response Group, which tracks the vaccine rollout.
While 83,597,242 jabs in total have been given out in England since the start of the vaccine rollout, some 28 million people in England will be eligible for their boosters when sufficient time has elapsed after their second dose.
Numbers released at the end of September by Public Health England estimated jabs had prevented 261,500 hospital admissions among people aged 45 and over, while the number of deaths prevented by the rollout in England was estimated to be 127,500.
Professor Neil Ferguson, a leading member of the Scientific Advisory Group for Emergencies (Sage), said that it is “critical” that the booster programme is accelerated.
Ferguson, from Imperial College London, said there is a need to speed up boosters and the vaccination of teenagers, who he suggested should be given two doses of a jab to block infection and transmission.
He also said the government’s ‘Plan B’ winter plan – that would involve reinstating work-from-home guidance, introducing strict vaccine-only entry conditions for some venues and events, and making it mandatory to wear masks in crowded places and on public transport – could be introduced.
Downing Street has said it has no plans to bring in tougher restrictions or impose another lockdown.
A No 10 spokesman said: “We have set out our autumn and winter plan in terms of ‘Plan A’ and ‘Plan B’, and we continue to look at the latest scientific data.
“There isn’t any proposed plan for any further lockdowns. We are sticking to the autumn and winter plan we have set out.”
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