Children with seasonal flu should not take antiviral drugs like Tamiflu because the risk of side-effects might outweigh the benefits of reducing symptoms, according to a new study.

In Monday's online issue of the British Medical Journal, researchers concluded the antivirals shorten the duration of flu in children between the ages of one and 12 by up to 1.5 days but had little effect on reducing asthma flare-ups or bacterial infections.

"While morbidity and mortality in the current pandemic remain low, a more conservative strategy might be considered prudent, given the limited data, side-effects such as vomiting, and the potential for developing resistant strains of influenza," Dr. Matthew Thompson from the University of Oxford and his colleagues concluded.

They reviewed seven previous studies on the use of the antiviral drugs oseltamivir (Tamiflu) and zanamivir (Relenza) for seasonal flu.

Tamiflu was linked to an increased risk of vomiting, which can be serious in children. The team concluded if 20 children were given the drug, one could be harmed by the side-effect.

During seasonal flu, children are at high risk, with over 40 per cent of preschool and 30 per cent of school-age children getting the virus. School-age children are the main source for spreading flu to households, the study's authors noted.

"Neuraminidase inhibitors provide a small benefit by shortening the duration of illness in children with seasonal influenza and reducing household transmission," the team concluded.

"Their effects on the incidence of serious complications, and on the current A/H1N1 influenza strain remain to be determined."

The review looked at four trials of 1,766 children treated with antivirals, including 1,243 with confirmed flu, and three trials of 863 who were exposed to flu but didn't exhibit symptoms and were treated with antivirals preventively. Only one trial looked at children with asthma.

Healthy children studied

Governments worldwide have been stockpiling antiviral drugs to deal with the current swine flu pandemic.

"Health Canada has concluded that the known and potential benefits of Tamiflu outweigh the known and potential risks for children under one year," the Public Health Agency of Canada says on its website.

"We know that Tamiflu thus far is effective in treating the vast majority of people who have H1N1, making their symptoms less severe and the illness lasting fewer days. We now have some evidence that there seems to be less risk in using Tamiflu in young children."

An influenza expert at the U.S. Centers for Disease Control noted the children in the studies reviewed were previously healthy kids. These children arguably are in least need of the drugs, compared with those at high risk because they are under six months old or have suppressed immune systems, Dr. Tim Uyeki said from Atlanta.

Prof. Robert Booy of the National Centre for Immunization Research and Surveillance at the University of Sydney, agreed with the study's authors that children with mild symptoms don't need treatment.

"Tamiflu, like any drug, has side-effects, and nausea and vomiting are prominent amongst them. However, it should also be recognized that influenza itself can cause nausea, vomiting and diarrhea, and this seems to be more common with the swine flu strain causing the current pandemic," Booy said.

"Overall, Tamiflu and Relenza are safe and effective drugs that are generally well tolerated."

With files from The Canadian Press, Australian Broadcasting Corporation