Giving children a flu vaccination could reduce its spread among older people, research suggests.

The Health Protection Agency said an annual jab for children under five could help protect the whole population.

As children have lower immunity and come into close contact with family and each other they are often prolific spreaders of the virus.

But the side-effects of the vaccination in children are not yet known, according to the Joint Committee on Vaccinations and Immunisation (JCVI).

In 2005 the committee advised that more work needed to be done before flu immunisation in children could be considered.

Dr George Kassianos, immunisation spokesperson for the Royal College of GPs, told the BBC that the college had been calling for the introduction of influenza vaccination in children for the past five or six years.

He said: "The children themselves fare very badly from influenza but they are also the source of infection for many adults.

"There is an urgent need for the JCVI to review their decision."

Professor Steve Field, chairman of the Royal College of General Practitioners, said vaccinating young children could be beneficial but that more research was needed.

He said: "This vaccination would need to be given every year to be effective.

"We know that influenza affects the vulnerable - the elderly and the young - and we also know that flu causes a lot of problems in terms of health and also with the economy, with people being off work and so on.

"We welcome this (HPA) analysis but also believe that extra work needs to be done."