This early increase has prompted concerns of flu spreading into the wider population in the coming weeks and triggering a “long and drawn-out flu season”.
UKHSA said it had no plans to issue guidance recommending school closures.
Duncan Burton, the chief nursing officer for England, said: “This early rise of flu in children is particularly concerning – especially given that flu circulation in children normally precedes that in adults – so it’s vitally important those eligible come forward for their vaccine as soon as possible to avoid a long and drawn-out flu season.
“The flu virus changes every year, so it’s important to get a vaccination each year to ensure yours and your families’ protection and to help reduce the spread to others.
“Vaccines are one of the safest and most effective ways to help shield against the virus and prepare for what we expect to be a very challenging winter, so I would urge everyone eligible to come forward for their jabs as soon as they can, with easy to book appointments or drop-in sessions now available closer to home.”
All eligible adults should aim to have received their flu vaccination by the end of November.
Vaccines are available for everyone aged 65 and over, under-65s in clinical risk groups, care home residents and carers, pregnant women, close contacts of those who are immunosuppressed and frontline health and social care workers as well as children.
Appointments and walk-in sessions are available in local pharmacies, GP practices and community clinic drop-in centres across the country.
Parents are also reminded to complete their child’s vaccination consent forms to schools, or to book an appointment for 2 to 3-year-olds to ensure their child gets vaccinated against flu before the Christmas period.
Dr Alex Allen, a consultant epidemiologist at UKHSA, said: “We’re seeing an unusually early start to the flu season this year, with the latest data showing a sharp increase among children but also increases in other age groups, with the virus now starting to spread more widely in the community.
“If you’re eligible for a vaccine it is because you are at greater risk of severe illness – every year, we see many thousands end up in hospital and far too many deaths from flu. It’s crucial that everyone eligible books their appointment as soon as possible. The vaccine is our best defence.”
Rory Deighton, the acute and community care director at the NHS Confederation, said: “The flu season arriving early this year is deeply worrying, given that the signs were already pointing to another difficult winter.
“The NHS has already had a very busy summer and has been running hot coming into the winter months, so this will pile yet more pressure on already squeezed services.”
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