Credit: Harvard Gazette Online

The tests on the flu vaccines reveal no signs of abnormalities so far, as health authorities continue investigation into the bad flu vaccine reaction scare in WA.

Jim Bishop, chief medical officer of Australia said the rise of cases of fits and fever among young children in WA could be possibly due to higher number of vaccinations being performed for young children in that particular state.

Altogether, there have been 57 cases reported in WA, compared to six in Victoria, 4 in NSW and Queensland, 2 in South Australia, and one case reported each in the ACT and Tasmania.

Prof Bishop said tests performed by drug manufacturer, the Therapeutic Goods Administration (TGA) and a number of various independent experts have not been successful to find a possible cause.

We don't have evidence at this time that there's any abnormality with the batch or with the vaccine, said Prof Bishop.

The health authorities will be at a better chance of grasping the complete picture once the investigations come to an end next week.

All the states and territories have been asked to go through past records to find for more related cases that might have been overlooked.

About three million doses of seasonal flu vaccine have been distributed this year, with nearly up to two-thirds were sent to WA, said Prof Bishop.

He believed this could provide a partial explanation as the most number of cases were observed with a much higher rate of complications in the western state.

Unlike the rest of the country, only West Australia offers free seasonal flu vaccine for children under five.