FDA Workshop on Standards

for inactivation and clearance of infectious agents in vaccine development

excerpt— As the situation with retroviruses indicates, there can be real problems in source materials that may have an outcome that is only apparent many years later and may not necessarily be easy to tie to the source material.

CDC

Adventitious agents and vaccines

excerpt— In the past, biologic products have served as vectors for viral diseases. Examples include:

1. the contamination of yellow fever vaccine with hepatitis B virus in the 1940s (because a human-derived excipient contained hepatitis B virus),
2. contamination of early polio and adenovirus vaccines with simian virus 40 in the late 1950s and early 1960s,
3. contamination of blood products with hepatitis viruses and HIV, and
4. contamination of dura mater grafts with the Creutzfeldt-Jakob disease agent.

In these examples, either human or animal materials used in production usually caused the contamination.