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An Australian study into the effectiveness of a H1N1 swine flu vaccine has revealed a single dose produces an excellent response against the virus in most children.

The study, led by Professor Terry Nolan, Head of the Vaccine and Immunisation Research Program at the University of Melbourne and the Murdoch Childrens Research Institute, and colleagues in major children’s hospitals around Australia has been published today in the Journal of the American Medical Association (JAMA).

“This influenza vaccine has shown an excellent level of protection against influenza in children following a single dose, although health authorities around the world have recommended two doses to provide optimum protection against this unpredictable infection,” Professor Nolan said.

“However, a single dose could be a viable option in the future.”

Results of the trial demonstrate a robust immune response after a single dose in children as young as six months of age, which is further enhanced by the administration of a second dose given three weeks later.

The clinical study included 370 healthy infants and children aged six months to nine years located in Melbourne, Perth, Adelaide, Sydney and Brisbane. Participants were divided into two groups, and given either a 15 microgram or a 30 microgram dose of the vaccine, produced by Australian biopharmaceutical company CSL.

A second dose was given to each group three weeks later. Blood samples to test protective antibody levels were taken before the first dose, and following each dose of vaccine.

Analysis shows that following the initial dose, 15 microgram induces protective antibody levels in 92 percent of children aged six to 35 months; and 92.9 percent in children aged three to nine years. After a second dose, 100 per cent of children in both age groups had protective antibody levels. Immune responses were robust regardless of age, baseline immune status, or seasonal influenza vaccine immunisation status.

The vaccine was well-tolerated by the children studied, with minor adverse effects very similar to that seen with seasonal influenza vaccines. No safety concerns were noted in the study

“As influenza can be a very severe disease in young children which spreads rapidly in those attending school or daycare, the published results of this trial are important and timely,” Professor Nolan said.

‘Vaccinating children is a significant component of reducing influenza transmission in the community. We are continuing to see outbreaks of H1N1 influenza in the Northern Hemisphere. Therefore, we cannot assume the threat of the disease has passed in Australia.’

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