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TSE risk assessment for starting materials used during, or in the manufacture of vaccines for human use--a consultant's view of the commercial approach.

Vaccination is an essential tool to protect humans from many infectious diseases. Materials derived from bovine tissues are used in, or during the manufacture of, most vaccines. Following the occurrence of BSE in cattle in three continents since 1986, the need to ensure the TSE safety of vaccines is vital. Various actions have been taken to ensure safety targets are reached. This paper shows that selecting starting tissues used in vaccine manufacture on the basis of their inherent TSE risk is of prime importance and is more secure than using geography as the primary criterion of a safe origin. Other approaches can also contribute to safety assurance. These include avoiding, where possible, tissues from animals, risk tissues and tissues of unknown or uncertain provenance. It is essential to ensure tissues are collected and processed appropriately and detailed records are kept. The risk assessment approach, based on the main safety factors of Source, Process and Use, coupled with these additional features, combine to establish that the TSE safety of vaccines is ensured, despite the challenge resulting from the occurrence of BSE.