Bookings for coronavirus booster jabs are opening this week for people aged 40 and over.
Sixteen and 17-year-olds will also be able to book in for their second jab from Monday.
Taking up the offer of a second or third dose will help protect the progress of the vaccine rollout in the face of waning immunity, and mean people can “enjoy Christmas safely”, the Department of Health and Social Care said.
Jabs should help to keep the coronavirus surge seen in parts of Europe “at bay”, Health Secretary Sajid Javid said.
People eligible for a booster can get the top-up jab from six months after having their second dose.
But they can book their appointment from 7am on Monday when the National Booking Service opens for people aged 40 and over, as well as for young people aged 16 and 17 in England.
Almost 200,000 teenagers in this category are currently eligible for a second jab, NHS England said.
It added that almost 500,000 people aged in their 40s are currently eligible for a booster, having had a second jab at least six months ago.
Bookings can be made online or by calling 119. Anyone eligible for a booster and at, or past, the six-month mark can use the NHS online walk-in finder to see their nearest walk-in site.
More than a million 40 to 49-year-olds can pre-book their appointments from Monday, and a further 1.5 million invites will be sent to this age group in the coming weeks, NHS England said.
Last week, England’s deputy chief medical officer Professor Jonathan Van-Tam said while vaccines have saved “countless lives and helped restore our freedoms in an unprecedented way”, it is clear “protection will wane over time after the first two doses of a primary course – that is especially so in older adults and those with risk conditions”.
He said the waning is also beginning to show in the 40 to 49 age group, something he would expect to increase in the absence of boosters.
He made the comment as the coronavirus booster programme was extended to over-40s across the UK.
More than 14 million boosters and third doses had been administered in the UK as of Friday, the Government said, with more than one million top-up jabs recorded since Tuesday.
Mr Javid, who had his booster last week, said: “Getting your Covid-19 booster vaccine is the best way to keep yourself and your loved ones safe this winter and will help reduce the pressure on the NHS.
“While the Government is continuing to monitor a wide range of data to ensure the country remains protected, we have very sadly seen a surge in cases in parts of Europe.
“The most important thing we can do to stop a similar rise in this country is get the jab – so please get your vaccines as soon as you can so we can keep the virus at bay.”
Professor Stephen Powis, NHS national medical director, said: “I’ve had my booster and I would urge everyone to get their vaccine whether their first, second or top-up dose as soon as possible, giving them and their loved ones vital protection over winter and the festive period.”
Vaccines minister Maggie Throup said people must make efforts to “protect the gains we have made through our vaccination programme this winter”, by coming forward for boosters when eligible.
Dr Emily Lawson, head of the NHS Covid-19 vaccination programme, said: “In the run-up to the festive period and what we know will be a challenging winter, I would encourage everyone who is eligible and invited to take up the offer of a life-saving booster as soon as possible to protect yourself and those around you.”