More than 600,000 people in England will be invited for a COVID-19 booster jab next week.
Since the beginning of the spring booster programme last week, NHS England said more than 470,000 people have already come forward for a jab.
Around 5.5 million people in England aged over 75 or immunosuppressed will be eligible for a spring booster over the coming weeks and months.
It comes as infection levels reach near-record highs in England, with around one in 16 people in private households in England – or 3.5 million people – likely to have had COVID-19 in the week to 19 March.
The figure, from the Office For National Statistics, is up from the one in 20 people – or 2.7 million people – who had the virus in the previous week.
It is also the third consecutive week that infections are estimated to have risen.
Health and Social Care Secretary Sajid Javid said: “I’m so grateful to our brilliant NHS staff and volunteers who have sprung into action yet again to rollout Spring boosters to keep the most vulnerable safe.
“Vaccines remain our best line of defence against this virus, and it’s thanks to these protections that we are all able to do the things we love.
“With hundreds of thousands more invites being sent to eligible people this week, it’s vital to come forward as soon as you can.”
People should wait to be invited before trying to book their spring booster, with the Joint Committee On Vaccination And Immunisation recommending that eligible people get their vaccine six months after their first booster.
The rise in infections in recent weeks is being driven by the Omicron BA.2 variant – a more transmissible form of Omicron, the ONS said.
The increase is being seen in all age groups and regions.
Infections among those over 70 are at their highest since estimates began in England in May 2020, with around one in 20 (5%) likely to have the virus – up week-on-week from one in 30 (3.5%).
Around one in 12 (8.3%) of those aged between two and school year 6 are estimated to have had the virus last week – up from one in 16, or 6.3%.
Dr Nikki Kanani, deputy lead for the NHS Vaccination Programme, said: “Over the course of the pandemic, vaccinations have been key to helping society get back to normal and allowing us to enjoy time with friends, family and loved ones – and they continue to play a crucial role in protecting us all against COVID, so please do book in when invited.”