Greater Manchester is experiencing a 'severe' wave of flu infection.
Flu admissions continue to climb, prompting NHS Greater Manchester to launch a series of walk-in, catch-up vaccination clinics.
The clinics are aimed at children aged two to three who have not yet received their vaccine through their GP, as well as school-aged children up to Year 11 who missed the vaccine at school or are home-schooled.
Dr Helen Wall, clinical director for population health at NHS Greater Manchester, said: "Every year thousands of people get really sick and end up in hospital from flu - and this year we are seeing it more than ever.
"That's why we are holding free walk-in catch-up flu vaccination clinics for any two and three-year-olds who've not been vaccinated by their GP and school-aged children who have missed the vaccinations happening at their school or who are home-schooled - to ensure as many children as possible are protected.
"The vaccine is still our best defence against flu, but the virus changes every year, which is why it is so important to get the new vaccine each year to stay protected."
The walk-in clinics are open from Friday, December 12 to Thursday, December 30, and are being held in areas with lower uptake, including Oldham, Tameside, Manchester, Salford, Bolton, and Bury.
Most children will be offered the nasal spray vaccine, but an injection is available for those who cannot receive the live vaccine or prefer not to for cultural reasons.
The flu virus changes each year, making annual vaccination essential.
Dr Wall said: "For most children this means getting a quick and painless spray vaccine rather than an injection.
"So, if your children have missed getting the flu vaccine at their school this year or are home-schooled, I urge you to please book them an appointment at one of the flu clinics taking place in December to ensure they have the protection they need to fight this virus and to keep those around them safe."
Parents and carers are encouraged to use the clinics if their child has not yet been vaccinated, unless a school clinic is still scheduled.
For questions or concerns, Intrahealth, the NHS vaccination partner, can be contacted by phone at 03333 583 397 or by email at contactimms@intrahealth.co.uk.
More information about the walk-in clinics is available at the Greater Manchester Integrated Care Partnership website under Children's catch-up flu vaccination clinics.