Risk of infection is zero, medical experts assert

The Government's medical experts are convinced the polio vaccine administered to between 50,000 and 60,000 Irish children is safe. Their confidence comes from the way the vaccine is manufactured and also because of the small amount of infective material that might have been introduced before processing.

A man who donated plasma for the vaccine later developed variant Creutzfeldt-Jakob disease (vCJD). The disease, the human form of BSE, is invariably fatal.

But the plasma would have undergone filtering to remove any infective material, according to the chairman of the Government's CJD advisory committee. "In my view it is zero risk," Prof William Hall said.

The vaccine is made by producing a weakened strain of the live polio virus and adding this to a "stabiliser", albumin, which is collected from human blood donations.

Albumin supplies are pooled so that large batches of finished vaccine can be produced. The vCJD donor was one of 63,866 who contributed plasma to the pool of albumin used in the polio vaccine, so any infective material would have been significantly diluted, Prof Hall said.

The processing methods would subsequently have cleared anything that could cause illness, he added. Repeated filtering leaves only pure albumin behind.

Prof Hall said the process had been tested by one of the world's leading experts on CJD, Dr Paul Brown of the US National Institues of Health.

"Everyone who has done work on this so far has shown no infectivity," said Dr John Devlin, the Department's deputy chief medical officer.