Around two million children in the UK will be offered the nasal spray vaccine as part of the programme to vaccinate 19m people in England, including expectant mums, the elderly and those with long-term illnesses.
Children are known as 'super-spreaders' so by preventing large outbreaks of flu spreading through nurseries and primary schools, families may be protected as well.
This year four-year-olds are being added to the vaccination programme but the aim is that all children will be given the annual vaccine eventually.
Only four in 10 children aged two and three last year were vaccinated.
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Nick Phin, Head of Respiratory Diseases at Public Health England, said: "The decision to include four-year-olds as part of the national roll-out is part of a long term plan to see the vaccine given to all children aged between two and 16.
"Flu is unpleasant for children as they suffer the same symptoms as adults including aching muscles and fever.
"Vaccination interrupts the spread of flu providing indirect protection to those most vulnerable including the elderly and anyone with an underlying health condition."
Professor Dame Sally Davies, the Chief Medical Officer for England, said: "Flu is a really unpleasant illness, particularly for our most vulnerable patients and it is essential that people take steps to protect themselves during the winter months.
"I would urge those who are offered the free flu vaccination to visit their GP early in the flu season. I also urge all health care workers to make they are vaccinated to protect themselves, their patients and their families".
Dr Paul Cosford, Director for Health Protection and Medical Director at Public Health England said: "The nasal spray is quick, easy and painless way to help prevent preschool age children catching flu and the vaccine also helps to reduce the spread of flu to those who are more vulnerable.
"People with certain long-term health conditions are at much greater risk of becoming seriously unwell if they catch flu and sadly, many end up in hospital.
"The best way people can protect themselves from flu is to take up the offer of free vaccination from their GP as soon as it becomes available.
"Even people whose health conditions are well managed and who lead otherwise healthy lives should still have the flu vaccine – it's free because you need it.
"Last year, around 40 per cent of pregnant women protected themselves and their baby from flu by getting vaccinated. This year we want to see more pregnant women and their babies protected...
"Women can safely have the vaccine at any point during pregnancy and it can reduce the risk of complications such as pneumonia and premature birth, that can arise as a result of flu."
Dr Carol Cooper, leading GP and broadcaster said: "I am often surprised by the low uptake of the flu vaccination within certain groups, and there is a great need for more awareness to ensure those eligible take up the offer.
"For example, mothers of children aged two to four may not know about the nasal spray vaccine, a quick, effective and painless option, which eliminates the need for needles."
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