More than half of children taking Tamiflu suffer side-effects such as nausea, insomnia and nightmares, researchers said.
Two studies from experts at the Health Protection Agency (HPA) showed a "high proportion" of British schoolchildren reporting problems after taking the anti-viral drug.
Data was gathered from children at three schools in London and one in the South West who were given Tamiflu earlier this year after classmates became infected.
The researchers behind one study said that, although children may have attributed symptoms that were due to other illnesses to the use of Tamiflu, "this is unlikely to account for all the symptoms experienced".
