This eighth and final report of the Immunization Safety Review Committee examines the hypothesis that vaccines, specifically the measles-mumps-rubella (MMR) vaccine and thimerosal-containing vaccines, are causally associated with autism. The committee reviewed the extant published and unpublished epidemiological studies regarding causality and studies of potential biologic mechanisms by which these immunizations might cause autism. Immunization Safety Review: Vaccines and Autism finds that the body of epidemiological evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism. The book further finds that potential biological mechanisms for vaccine-induced autism that have been generated to date are only theoretical. It recommends a public health response that fully supports an array of vaccine safety activities and recommends that available funding for autism research be channeled to the most promising areas. The book makes additional recommendations regarding surveillance and epidemiological research, clinical studies, and communication related to these vaccine safety concerns.