Parents of children aged two and three are being urged to book them in for a nasal flu vaccine.
NHS England will contact more than a million parents and carers from Tuesday to tell them the nasal spray vaccine is available.
Children are usually given the flu vaccine through a quick and painless spray up the nose.
But anyone who cannot have porcine gelatine in medical products is offered an injection instead.
Schoolchildren and other groups such as pregnant women, older people and those with health conditions will be able to get a vaccine ahead of winter, when cases spike.
Flu tends to peak in December and January and people are advised to have a vaccine before then.
It can be serious and can lead to hospital admission, even in young children.
Last year some 2,478 patients were in hospital with flu each day during the peak of winter flu cases, 2.5 times higher than the previous year, NHS England said.
It said Australia’s flu season, which normally predicts how seasonal viruses will affect England in winter, has seen a big wave of COVID-19 infections alongside a rise in flu and other winter illnesses.
In the current phase, pregnant women and children aged two or three as of 31 August this year can have a flu vaccine, alongside all schoolchildren and any youngster in a clinical risk group.
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From next month, vaccines will be rolled out to anyone in England aged 65 and over, those aged 18 to 65 in clinical risk groups, and those in care homes. Online bookings open on 23 September.
People such as carers in receipt of carer’s allowance and those who are the main carer of an elderly or disabled person can get a vaccine on the NHS, as can those who are close contacts of immunocompromised people.
Other eligible groups include NHS workers and carers working in care homes.
Steve Russell, NHS national director for vaccinations and screening, said: “The flu vaccine is our best defence against these winter viruses, as well as helping to reduce pressure in hospitals over the winter period as demand increases.
“The flu virus puts thousands of people in hospital each year and vaccinations help us to keep more people well so I would urge everyone eligible to book their jabs when they become available, to protect themselves and people around them.”