Health officials in Australia say the number of children suffering adverse reactions to the flu vaccine may be severely underestimated because they have no way of monitoring people's reactions.
The ABC reports a child is critically ill and dozens more suffered serious adverse reactions after receiving the vaccine in Western Australia.
Other states, including Queensland and South Australia, are also reporting incidents of children being hospitalised and having adverse reactions such as fevers and convulsions.
Queensland Health says three children are in hospital and 41 have had adverse reactions, but only 15 of those cases were children under the age of five.
