By Michelle Roberts
BBC News health reporter
A leading doctor has questioned the government's policy of not offering routine flu jabs for the under-twos.
Parents may be concerned if their children have to have more jabs
Dr George Kassianos, the Royal College of General Practitioners' immunisation expert, argues vaccinating infants would prevent illness and save lives.
The US already offers the jab to children aged six months to five years.
But UK government advisers said it was unclear if a similar policy would cut the flu burden enough, given the cost of a vaccination campaign.
The US introduced shots for young children on the assumption that it will reduce flu transmission and cases in both children and adults.
In the UK, those hit hardest by flu - people aged over 65 and those, including infants and children, with other health problems such as asthma - are already offered free jabs.
But the expert advisory body, the Joint Committee on Vaccination and Immunisation (JCVI), has so far rejected the idea of giving the jab to all children.
However Dr Kassianos said routine childhood immunisation should be considered.
"Children do fall ill with influenza and some even die as a result."
Up to 10 to 15% of the population may develop influenza in any one year, varying from year to year
Even during a winter where the incidence of flu is low, 3-4,000 deaths may be attributed to flu
Deaths can rise much higher during an epidemic - there were an estimated 29,000 deaths in 1989/90, including the under twos
Flu is not usually life threatening for healthy people
And he added: "Young children bring flu home from school and playgroup. That is why the US has introduced the vaccine universally.
"I would have preferred the JCVI to have allowed us to routinely vaccinate children age six months to at least three years.
"If we can take it to five years like the Americans, even better."
"It would have an impact on adult transmission and circulation of the virus in the community."
He said the vaccine did work in children, although infants need two doses in the very first year they get the jab.
Dr Kassianos added: "While we understand that there might be logistical problems with extending the influenza immunisation recommendations, these can be overcome with support."
Critics, including the European Centre for Disease Prevention and Control's scientific panel on vaccines and immunisation, question the ethics of exposing a healthy child to the risks of a flu jab for a policy that would mainly benefit adults.
The JCVI has so far rejected the idea because studies had suggested the jab might not work as well in children.
It has also said it is unclear whether children play a big role in spreading the virus to vulnerable groups like the elderly - a factor the JCVI says is critical for the policy to be cost effective for the NHS.
The data considered by the JCVI suggested the number of people falling ill with flu would go down by a fifth if 60% of children aged six months to two years were immunised against common flu strains A and B.
But many of the assumptions were based on US findings, which the committee argued might not hold true in the UK.
The JCVI wants more research to be carried out before it can recommend the jab to ministers. It is set to consider the issue again at a meeting in March.
Flu expert Professor John Oxford, from Queen Mary's School of Medicine, agreed that infants were responsible for passing flu on to adults and that vaccinating the under-twos would save both child and adult lives.
But he said the JCVI had probably made the right decision to be cautious given the lack of UK data and the public's reticence about vaccines.
The Department of Health said it would not make a decision until the JCVI had presented its recommendations.