Nearly 500,000 vaccine appointments were booked by midday on Tuesday in a “Glastonbury-style” rush after the rollout was expanded to 25- to 29-year-olds in England, the NHS said.
The National Booking Service saw 493,000 slots reserved, five hours after eligibility was widened to the over-24s.
It is more than double the number booked the previous day and equates to about 100,000 bookings an hour.
Sir Simon Stevens, the chief executive of NHS England, said: “This encouraging Glastonbury-style rush for appointments has already now seen hundreds of thousands of people between 25 and 29 book in for their NHS Covid jabs, as more vaccine supplies continue to come on line.
“Pleasingly, this suggests strong enthusiasm for vaccination amongst people in their 20s, following hard on the heels of the millions of others who’ve already taken up our offer.”
The health secretary, Matt Hancock, said: “I am absolutely thrilled young people have come forward for the jab in full force today. We have one of the highest vaccine uptake rates in the world and these latest booking figures are testament to this.”
However, many young people reported problems with the booking website this morning, with some posting screenshots to social media showing an error message telling them that they are “not currently eligible to book through this service”.
It directs them to call the 119 helpline to try to book a vaccination. Others reported being told they were in a queue of thousands.
A spokesperson for NHS Digital said: “Large numbers of people are currently booking their vaccine appointments through the NHS website, which means you may need to wait in a queue.
“We know that some people have been receiving an ineligible message when trying to book, which is being fixed now, so please retry.”
The vaccine booking website has suffered glitches previously, including crashing in April after appointments were being opened up to the 45s and over.
Elsewhere, Andy Burnham, the mayor of Greater Manchester, urged the government to speed up vaccine supplies to his region to allow it to run a “surge vaccination programme”.
He spoke after the government announced that surge testing will be extended in Greater Manchester and Lancashire in response to the rise in Covid cases in those areas.