Bovine-derived materials have traditionally been used in the manufacture of many biological products, including vaccines. Bovine spongiform encephalopathy (BSE), so-called "mad-cow disease," was first recognized in the United Kingdom (UK) in the 1980s(1). The Center for Biologics Evaluation and Research (CBER) of the U.S. Food and Drug Administration (FDA) has been concerned about eliminating any potential for contamination of biological products with the BSE agent This concern was heightened by the appearance of the human transmissible spongiform encephalopathy known as variant Creutzfeldt-Jakob Disease (vCJD, also referred to as new-variant CJD) in the UK in 1996; vCJD has been attributed, among other possibilities, to eating beef products from cattle infected with the agent of BSE (2). To date, there are no reports of BSE contamination of pharmaceutical or biological products. To minimize the possibility of contamination in such products, the FDA, in 1993 (published in the Federal Register on August 29, 1994, 59 FR 44591), and again in 1996, recommended that manufacturers not use materials derived from cattle that were born, raised, or slaughtered in countries where BSE is known to exist; the FDA referred manufacturers to the listing of such countries that is maintained by the U.S. Department of Agriculture (USDA)(3).
In 1991 the USDA list included only countries and other regions in which BSE was known to exist, such as France, Great Britain, Northern Ireland, the Republic of Ireland, Oman, and Switzerland. In 1998, the USDA expanded the list to include countries and other regions in which BSE had not been documented but in which import requirements were less restrictive than requirements that would be acceptable for import into the United States or in which surveillance was inadequate. Thus, all European countries, even those that have had no reported BSE cases, are currently on the USDA list, which is published in the Code of Federal Regulations, title 9, part 94 (9 C.F.R. part 94).
Earlier this year, CBER learned that its recommendations regarding the sourcing of bovine materials for the manufacture of vaccines had not been followed in at least one instance. As a result of this finding, CBER requested all vaccine manufacturers to review the source for all bovine-derived materials used in the manufacture of their vaccines. This review identified additional vaccines manufactured with bovine-derived materials that had been obtained from European countries on the USDA list.
No evidence exists that any case of vCJD has resulted from the administration of a vaccine product(4), and no cases of vCJD have been reported in the United States. To evaluate the risk of disease that might result from a vaccine manufactured with a process that
utilizes bovine materials potentially contaminated with the BSE agent, CBER
conducted risk assessments and convened a special joint meeting of the Transmissible Spongiform Encephalopathy Advisory Committee and the Vaccines and Related Biological Products Advisory Committee on July 27, 2000. In assessing the potential risk of vaccines, CBER and the joint Committees considered: (1) the likelihood that any cattle that were used might be infected (i.e., the time period and country of origin) and animal husbandry procedures; (2) the amount of bovine material that might be present in the final vaccine; and (3) the inherent infectivity of the various types of bovine materials that were used. The joint Committees concluded that the risk of vCJD posed by vaccines in the scenarios that were presented was theoretical and remote. They also noted that the benefits of vaccination far outweigh any remote risks of vCJD. The joint Committees made several
- Bovine-derived materials used in the routine production
of vaccines that are sourced from countries on the USDA list should be replaced with bovine-derived materials from countries not on the USDA list.
- Working bacterial and viral seed banks and working cell
banks that were established using bovine-derived materials sourced from
countries on the USDA list should be re-derived with bovine-derived materials from countries not on the USDA list. However, master bacterial and viral seed banks established in a similar manner do not need to be re-derived; the potential risk presented by the master seed banks is even more remote than that presented by the working seed banks and is outweighed by the risk of altering the bacterial or viral vaccine through re-derivation.
- These issues are of public interest and, therefore, the
public should be informed about the safety of vaccines that used materials
sourced from countries on the USDA list, and the assessment of the nature of
any risk of vCJD from such vaccines.
As noted above, there is no evidence that any case of vCJD has been caused by or is related to vaccines manufactured with bovine-derived materials obtained from countries in which BSE or a significant risk of BSE exists (i.e., countries on the USDA list), and thus the risk of vCJD is theoretical. The joint Committees’ recommendation to replace such bovine-derived materials with bovine-derived materials from countries not on the USDA list is a precautionary measure intended to minimize even the remote risk of vCJD from vaccines.
The vaccines that use bovine-derived materials from countries on the USDA listinclude: Aventis Pasteur, S.A.’s Haemophilus influenzae type b conjugate vaccine, ActHIB® (ActHIB® is also marketed as OmniHIB™ by SmithKline Beecham Pharmaceuticals); North American Vaccine Inc.’s diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccine, Certiva™ (the tetanus toxoid manufactured by Statens Seruminstitut for use in CertivaTM is the only component of the vaccine manufactured with bovine-derived materials from a country on the USDA list); SmithKline Beecham Biological’s DTaP vaccine, Infanrix®(the diphtheria toxoid manufactured by Chiron Behring GmbH & Co. for use in Infanrix® is the only component of the vaccine manufactured with bovine-derived materials from a country on the USDA list) and hepatitis A vaccine, Havrix®.
In some other cases, the source of the bovine-derived materials is unknown, in part because manufacturers have not always maintained or had access to records of the source of such materials, particularly in the 1980s and early 1990s, before the connection between BSE and vCJD was first suggested. Vaccines that use bovine-derived material of unknown origin obtained in 1980 or thereafter (the current best estimate is that BSE first emerged in 1980) include: Aventis Pasteur, S.A.’s inactivated polio vaccine, IPOL®; BioPort’s anthrax vaccine and rabies vaccine; Lederle Laboratories’ pneumococcal polysaccharide vaccine, PNU-IMUNE® 23.
Vaccines using bovine-derived materials from a country on the USDA list or from an unknown source to manufacture only the master seed are not listed above; the joint Advisory Committees indicated that master seeds need not be re-derived. Additional information on such vaccines can be obtained upon request.
The FDA has requested that manufacturers of vaccines using bovine-derived materials obtained from countries on the USDA list replace these materials with materials from countries not on the USDA list, consistent with the recommendations of the joint Advisory Committees. The manufacturers have agreed to fully implement these changes. Indeed, several manufacturers initiated a number of these changes before the July 27, 2000, joint Advisory Committee meeting. FDA anticipates that the majority of these changes will be completed within one year. The FDA will revise the list of vaccines using bovine-derived materials from countries on the USDA list or from an unknown source as the requested changes are implemented and the vaccines come to market. Get the full list in today's issue of Vidyya.
The Public Health Service (PHS) recommends that all children and adults continue to be immunized according to current immunization schedules(5). At the present time, the PHS has no preference for using one licensed vaccine product over another based on the source of bovine-derived materials used in vaccine production. The recommendations of the FDA Advisory Committees and the actions of the FDA are, as described,
precautionary and have been taken to reduce even the remote potential of a risk of vCJD and to maintain public confidence in the safety of vaccines. Failure to obtain the recommended vaccinations with licensed vaccines poses a real risk of serious disease.
- Wells G.A.H. et al. 1987. A novel progressive spongiform encephalopathy in cattle. Veterinary Record 121:419-420
- Spongiform Encephalopathy Advisory Committee of UK statement of 20 March 1996 (http://www.maff.gov.uk/animalh/bse/index.html)
- USDA 9 CFR part 94.18
- P. D. Minor, R.G. Will and D. Salisbury.2000. Vaccines and variant CJD Vaccine 19:409-410.