There has been and still exists a debate regarding whether vaccines administered at the start of an infant’s life have any connection to the development of autism. This has caused a major public health issue, after concerned parents began opting out of these initial vaccines, raising the chances of an outbreak of diseases such as measles, mumps, and rubella (MMR). Despite the claims of fervent believers, there have been countless studies that disprove this connection as entirely mythical. One meta-analysis in particular analyzed several cohort studies, which included over a million children, and reported there is no connection between autism and the MMR vaccine, thimerosal, or mercury.
Source: Taylor LE, Swerdfeger AL, Eslick GD. Vaccines are not associated with autism: an evidence-based meta-analysis of case-control and cohort studies. Vaccine. 2014 Jun 17;32(29):3623-9.