BSE risk associated with the use of materials of bovine origin during the manufacture of vaccines

3 September 2007

TGA has had a number of consumer enquiries concerning safety issues arising from the use of bovine materials in the manufacture of vaccines. The following questions and answers explain the BSE-related issues associated with vaccines registered by the TGA.

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BSE stands for Bovine Spongiform Encephalopathy and is a progressive neurodegenerative disease of cattle. BSE is also called mad cow disease. BSE first emerged in Great Britain in the mid 1980s. A total of around 200,000 cases of BSE have since been confirmed in UK cattle and BSE has also occurred in other European countries, Japan and North America.

An abnormal prion protein is considered to cause the disease. Prion proteins (PrP) are produced in normal animal and human cells. Abnormal prion protein forms into an infectious particle that can transmit the disease. Accumulation of the abnormal protein within the brain causes neurological deterioration.

BSE is one of a group of Transmissible Spongiform Encephalopathies (TSEs) or prion diseases that cause progressive fatal neurological diseases in animals and humans. TSE diseases in animals include Scrapie, which occurs in sheep and goats, feline encephalopathy in cats and chronic wasting disease (CWD) in deer and elk. There are 6 TSE diseases which occur in humans, the most frequent of which is Creutzfeldt-Jakob Disease (CJD), which occurs sporadically worldwide at a rate of about one case per million persons. A human TSE, known as variant Creutzfeldt-Jakob Disease (vCJD), was first identified in the UK in 1995 and is considered to be the human form of BSE. Up to July 2007, a total of 168 persons in the UK have acquired the disease. Only small numbers of confirmed cases of vCJD have been reported in persons living outside of the UK, such as in France, Ireland, Netherlands, Portugal, Spain, Italy, Saudi Arabia, Japan, Canada and USA giving a world wide total of 201. When compared to CJD, vCJD affects younger persons, has differences in clinical features including a longer disease course and some differences in changes in brain tissue structure.

Epidemiological and laboratory evidence provide strong support that vCJD and BSE are caused by the same agent. The time interval between initial exposure of the human population to the BSE agent and the initial cases of vCJD was around 10 years. Confirmed cases of vCJD have all been linked to geographic areas in which BSE occurred. Prions obtained from patients with vCJD and cattle with BSE show similar molecular characteristics however, the characteristics of prions obtained from patients with CJD have different molecular characteristics. [Nature 1996; 383: 685-90]. Experimental studies in which prion causing BSE was injected into monkeys and mice, showed brain tissue changes similar to those seen in vCJD [Nature 1996; 381: 743-4].

Vaccines used to prevent infectious diseases contain bacteria or viruses which have been killed or weakened, or contain components of the bacteria or viruses. These components stimulate a response by the immune system of the body which protects against the development of disease. The bacteria or viruses used are grown under controlled conditions in media, which provide nutrients for growth. Although fully synthetic media are adequate for the growth of many microorganisms, some microorganisms require additional nutrients, which are easily provided in animal derived products such as serum and blood. Meat extracts, tallow derivatives, gelatin, detergents and enzymes may also be used in manufacture of some vaccines.

Any bovine derived material used in the manufacture of a medicinal product is regulated according to the European CPMP Note for Guidance for minimising the risk of transmitting animal spongiform encephalopathy agents, as adopted by TGA. Since 1991 manufacturers have been advised of concerns about use of bovine derived materials from animals born in or residing in countries where BSE has occurred. During review for TGA registration, sponsors must provide detailed descriptions of manufacturing processes and information on the source of all materials used in manufacture. Some of the criteria used for safety assessment include control of the geographical source of the animals used, the nature of the tissue used and manufacturing processes that can/may inactivate BSE infectivity.

No case of vCJD from vaccines has been demonstrated. In Australia, there have been reviews of TSE safety in relation to vaccines and other medicinal products used in humans since 1995 after the first cases of vCJD emerged in the UK. In 2000, a review was initiated by Australia's Chief Medical Officer, following the withdrawal of an oral polio vaccine used in the UK. In 2001-2002 a comprehensive TGA review of all registered vaccines was conducted which was reported to and reviewed by the NHMRC Special Expert Committee on Transmissible Spongiform Encephalopathies (Transmissible Spongiform Encephalopathy Advisory Committee, TSEAC). All of these reviews have concluded, that vaccines used in Australia meet high safety standards and that any risk of vaccines being contaminated with BSE is extremely low. The benefits of vaccines used in Australia are also concluded to far outweigh any theoretical risk of vCJD transmission via vaccines.

Additional information on this topic is included in the US FDA website. This information includes details of the risk assessment process of the type that has been undertaken for each vaccine product registered in Australia.

Information is also available from the EMEA website:

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