Answer
The MMR (Measles, Mumps, Rubella) vaccine was the focus of Wakefield's study. Wakefield's research, published in 1998, claimed a link between the MMR vaccine and the development of autism, sparking significant public concern. However, subsequent investigations revealed flaws in the study's methodology and a potential conflict of interest. Numerous subsequent studies have found no evidence to support the link between the MMR vaccine and autism.