More than half the children in England taking the swine flu drug Tamiflu suffer side-effects such as nausea, insomnia and nightmares, researchers have found.
Two studies from the Health Protection Agency (HPA) show a high proportion of schoolchildren reporting problems after taking the antiviral drug.
Data was gathered from children at three schools in London and one in the south-west of England who were given Tamiflu to try and stop them developing swine flu after classmates became infected.
The researchers behind the study said while children may have attributed symptoms to the use of Tamiflu that were actually due to other illnesses, "this is unlikely to account for all the symptoms experienced".
Their research, published in the medical journal Eurosurveillance, looked at side-effects reported by 11 and 12-year-old pupils in a secondary school that was closed for 10 days after a pupil was confirmed to have swine flu after a holiday in Cancun, Mexico.