Health officials said that protection from polio was more important than avoiding a theoretical risk that once existed from vaccines using material from British cattle.

Members of the spongiform encephalopathy advisory committee (Seac), which advises ministers on BSE-like diseases, are satisfied the link is coincidental rather than causal.

They say millions of people have been inoculated using vaccines grown from foetal calf serum, and no evidence has emerged that people treated with vaccines based on material from British cattle since the 1980s have been more susceptible to variant CJD, the human form of BSE.

Deirdre Cunningham, a Seac member, said the committee had been worried that the finding "might affect whether parents wanted their children vaccinated. We thought the threat of a theoretical risk was no justification for ruining an immunisation vaccination programme."

But the revelation is still embarrassing to other officials responsible for monitoring manufacture of medicines.

The vaccine concerned should not even have still been on the market when it was administered to the variant CJD patients in 1994. Guidance dating back to 1989 said bovine material in vaccines should be sourced from BSE-free countries, even though it took four years for many older stocks to work through.

However, the polio vaccine remained on the market until October 2000 because the guidance only referred directly to injectable vaccines, not oral ones. Tough laws introduced this year closed the loophole.

Modified Saturday, November 29, 2008