Although food has been the overwhelming object of attention as the source of infection with variant Creutzfeldt–Jakob disease (vCJD), there is a possibility that some of the victims — who are predominantly young adults — might have contracted the disease through immunization.
The BSE inquiry's report (see above) calls for vaccines to be investigated as a possible route of transmission. But it concedes that this will be hampered by the fact that “systematic records of the action taken in response to BSE in respect of individual medical products are lacking”.
Indeed, the report reveals that the pharmaceuticals industry and related government agencies failed to grasp the extent of the risk, and delayed removing potentially harmful products from the public arena. It notes that this behaviour persisted longer than corresponding problems in the meat industry, without attracting similar parliamentary and public scrutiny.
Some vaccines are made using culture media derived from cattle tissue. Although guidelines asking drugs companies to get this material from countries with BSE-free herds were issued in 1989 by the Committee on Safety of Medicines (CSM), they will not become law until March 2001. Companies have been relied on to follow the guidelines voluntarily. Yet only last month, it emerged that one company, Medeva, had continued to use bovine serum from British herds to make an oral polio vaccine (see Nature 407 , 936; 2000). The Department of Health delayed release of this news for two months.
Alarmingly, vaccines produced after the point at which the BSE epidemic had been identified — possibly using British bovine material — were still in use as recently as November 1993. According to the inquiry's report, the chief medical officer of the day, Donald Acheson, decided to phase out the existing stocks because new batches of vaccines take time to grow, and medical experts considered that the benefit of maintaining a continuous national immunization programme outweighed the risk of interrupting it.
These decisions were taken in the absence of knowledge about how infective bovine materials used to make vaccines might be. It was only in 1993 that the Neuropathogenesis Unit in Edinburgh obtained test results that showed bovine serum did not cause infection in mice — studies that the inquiry's report describes as “inconclusive”.
But in some sections, the report is sympathetic to the difficulties of withdrawing medicines from use quickly. Product licences would have had to have been revoked on an individual basis, so each licence holder could have appeared before the relevant committee to argue against withdrawal. “This would have been a logistical nightmare,” says the report. “It is not surprising that the decision was taken to issue guidelines rather than attempt to use formal statutory powers.”
Last week it was also revealed that the Department of Health asked the CSM as recently as March this year to produce a comprehensive assessment of BSE-related issues in vaccines. There has been no indication when this evaluation will be made public.
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Follicular dendritic cell dedifferentiation reduces scrapie susceptibility following inoculation via the skin
Scrapie transmission following exposure through the skin is dependent on follicular dendritic cells in lymphoid tissues
Journal of Dermatological Science (2004)