Scientists examine CJD 'link' to polio vaccine

Senior British Government advisers yesterday sought to head off a potential public health scare after two people with the human form of BSE were found to have shared the same batch of polio vaccine.

Although the two victims of variant Creutzfeldt-Jakob disease (vCJD) both swallowed the oral form of the vaccine – which was made using bovine blood – scientists believe the cases are an unlucky coincidence.

Professor Peter Smith, chairman of the Spongiform Encephalopathy Advisory Committee (Seac), revealed that an investigation by scientists has failed to find evidence of a link between other cases of vCJD and the polio vaccine.

However, Seac scientists are concerned that even raising the possibility of a link between vCJD and the vaccine could turn parents away from childhood immunisation programmes which have already suffered bad publicity over alleged health risks.

"We were worried on the committee that this might affect whether parents would want their children to be vaccinated in this country," said Deidre Cunningham, a public health specialist and new member of Seac.

"We thought that an absolutely infinitesimal risk was absolutely no justification for ruining a vaccination and immunisation programme that actually does protect people's health," Dr Cunningham said.

The two vCJD patients are part of a group of five "geographically associated cases" in the Southampton area. Both patients were given oral polio vaccine from a batch distributed in 1994, six years prior to the vaccine being banned.

Each batch consisted of between 70,000 and 80,000 doses of vaccine and was part of a larger consignment of about 5m doses each made by an identical process of growing the vaccine in blood serum drawn from foetal calves.

The Department of Health recalled the vaccine in October 2000 after it discovered that it breached European guidelines banning the use of foetal calf serum from countries affected by BSE.

However, a comparison of patients with vCJD and healthy people failed to find evidence to suggest that the vaccine could have caused the transfer of BSE from cattle to humans.

"Looking at the cases as a whole, there is really nothing to implicate this source of polio vaccine. The committee did not think that this was in any way persuasive evidence for a link to the vaccine," Professor Smith said.

So far there have been 112 cases of vCJD and most of them have been in people younger than 30, the group most likely to have received polio vaccine over the past 20 years.

"Both of these individuals were young adults when they received the vaccine. The vaccine is generally given to infants but quite a lot of us should receive polio vaccine at later ages, as did these two individuals," Professor Smith said.

"The fact that two had received vaccine from this one batch did not strike us as a reason for really changing the advice that had previously been given," he said.

Both patients lived in the Southampton area, were of a similar age and could have shared many other features of their lifestyle, including diet. "It's highly likely that they would have had polio vaccine from the same batch – that's why we didn't attribute any particular significance to this," Professor Smith said.

Extensive tests have failed to find any evidence that BSE can be transmitted in the blood of adult cattle with the disease, let alone immature foetuses, said Ray Bradley, a veterinary scientist and member of Seac.

"We've tested many components of bovine blood and foetal calf blood by bioassay and can find no detectable infectivity in any of those materials," Mr Bradley said.

"Foetal calf serum is used in most viral vaccines at the stage where you grow the cells and there have been literally millions of bovine and ovine vaccines prepared in this manner and no evidence whatsoever that there's even been any transmission of BSE," he said.

- INDEPENDENT