The possible link between autism and vaccinations has generated a substantial amount of controversy within the media and scientific community. An article published in the Lancet by Andrew Wakefield and colleagues in 1998 played a significant role in creating concern about vaccine safety. This article, which was subsequently found to be fraudulent, suggested a link between the measles, mumps, and rubella (MMR) vaccine and autism. Following the article’s publication, a rise in vaccine-preventable diseases among nonimmunized individuals was observed. Another source of controversy in the vaccine–autism debate is thimerosal, a preservative used to prevent bacterial growth. Numerous large-scale studies have consistently found no link between MMR or thimerosal-containing vaccines and the development of autism. This entry introduces autism, explores the widespread public interest in the ...