Twelve million people over the age of 50 will be invited to book their Covid-19 and flu jabs from Friday.
Online and phone bookings for a Covid-19 booster will open on Friday for those aged 50 to 64.
Since the booster programme started a month ago, seven million people have come forward for their vaccine.
Some 26 million people are eligible for the Covid-19 booster and people have been urged to get the jab amid a warning of a potential “twindemic” of flu and Covid-19.
The NHS in England is testing whether people can book their flu jabs online, with people at 200 sites across the country being offered to book this way.
People successfully used the National Booking Service during the Covid vaccination programme, with those unable to get online given alternative ways to book.
Flu vaccinations can still be booked through GP practices or by visiting a pharmacy delivering the jabs.
Around 33 million people in England will be eligible for a flu vaccine this year, including some children who will be given the flu nasal spray.
Amanda Pritchard, NHS England chief executive, said: “Thanks to the incredible work of our front-line staff across the country, our Covid autumn vaccination programme continues to go from strength to strength as we open up eligibility to around 12 million more people from tomorrow.
NHS could face ‘extremely challenging winter’
“The rollout is off to a flying start – we have invited twice as many people as we did last autumn and we have jabbed twice as many people as we did last autumn.
“As we approach what could be an extremely challenging winter for the NHS, it is vital to get your protection against both Covid and flu, so please come forward and book in when you can.”
Steve Russell, director for vaccinations and screening, added: “More than seven million autumn Covid boosters have been administered so far thanks to the hard work of NHS staff and volunteers, and while this is a brilliant start, our work is not done as more than 12 million more people are now being invited to take up the offer and book an appointment as soon as possible.
“Vaccinations are our strongest weapon against these viruses and NHS staff are once again doing all they can to protect the public, including through a new trial that will allow people to book their flu jab through the National Booking Service.
“If you are between 50 and 64 then please do not hesitate to log on and book yourself an appointment, it is the best way to protect yourself from serious illness this winter.”
Dr Susan Hopkins, chief medical adviser at the UK Health Security Agency (UKHSA), said: “The double threat of widely circulating flu and Covid-19 this year is a real concern, so it’s crucial that you take up the free flu vaccine as soon as possible if you are offered it. It will help protect you from severe flu this winter and even save your life.
“All those over 50 are now eligible for the jab, many of which will have low natural immunity due to Covid-19 restrictions over the last two years.”