Toddlers should be vaccinated against flu, researchers have said, as a new study shows it protects seven in ten children.
Young children are particularly susceptible to flu and other infections and should be routinely vaccinated, researchers said in an article in Lancet Infectious Diseases.
In America and Finland young children have been vaccinated for several years but other countries have not followed due to a lack of data about the effectiveness of the vaccines in this age group.
Research conducted in Finland found the match of the flu strains in the vaccine to those circulating was more important for efficacy than the age of the patient.They found that overall the seasonal flu vaccine, which contains two A strains and a B strain of deactivated flu, was effective at preventing the disease in 66 per cent of cases.
Where the vaccine was well matched to the two A strains, this rose to 84 per cent.
This winter in Britain pregnant women are being offered the seasonal flu jab for the first time alongside the over 65s, those with long-term diseases and frontline healthcare workers.
The seasonal flu jab contains the H1N1 swine flu strain but is not the same vaccine that was produced for last year's pandemic.
The Department of Health began vaccinating healthy children under the age of five during the pandemic but experts have not advised that this age group be offered the seasonal vaccine this year.
This is despite the under twos being one of the groups hardest hit by swine flu during the pandemic and that the H1N1 strain is expected to be widespread again this winter.
Lead author Santtu Heinonen, of the Turku University Hospital in Finland, wrote in the journal: "In conclusion, our findings suggest that trivalent inactivated influenza vaccine is effective against influenza in young children, including those younger than two years, when there is a good antigenic match between the vaccine and the circulating strains.
"Together with ample evidence for the high disease burden of influenza in young children, our findings suggest that influenza vaccine recommendations should be reassessed in most countries."
The study involved comparing the number of laboratory-confirmed influenza A and B infections in 631 prospectively followed children aged 9 to 40 months old who did and did not receive the vaccine.
Overall, the effectiveness of vaccination was 66 per cent against any influenza, and 84 per cent against influenza A viruses.
In children younger than two years overall effectiveness of vaccination was 66 per cent, and 79 per cent against influenza A strains.
They found that in half of the cases of influenza, the children had caught a different B flu strain to the one included in the vaccine that year.
Larger studies, in different countries and involving different vaccines should be conducted they said.
In an accompanying commentary Mark Steinhoff from the Cincinnati Children’s Hospital Medical Center, in Cincinnati, said larger trials were needed 'to assess the cost-effectiveness of a strategy for universal immunisation for influenza in children and the broader effect for such a strategy on families and communities'.
Prof Adam Finn, of Bristol University and consultant in paediatric infectious diseases, said vaccinating young children against seasonal flu might be a way of preventing flu in the wider population as they are known as 'super-spreaders'.
He said: "It is possible that you might save more lives amongst the elderly by vaccinating young children.
"If I were looking to introduce vaccination I would use inactivated flu jabs between six months of age and two years and then other vaccines from two to five years."
Prof Finn added that flu is one of the top three reasons young children are admitted to hospital in the winter.
A Department of Health spokesperson said: “We welcome this study and the information it provides on the effectiveness of flu vaccine in young children. The Joint Committee on Vaccination and Immunisation will consider the findings.”