Claims that childhood vaccines fuelled an epidemic of autism were widely publicised in the late 1990s. One “theory” incriminated the measles component of the triple measles-mumps-rubella (MMR) vaccine, the second one implicated thimerosal (ethylmercury) received through other childhood vaccines. However, trends in rates of ASD were shown to be uncorrelated to trends in uptake of MMR or thimerosal-containing vaccines [
8]. Controlled observational studies (case-control and cohort studies) equally failed to show increased risk of ASD in individual children exposed to MMR or thimerosal-containing vaccines in various doses [
9]. Thimerosal was removed from vaccine production in the early 2000s, with no effect of autism trends. Younger siblings of children with ASD also have no raised risk of ASD after immunisations [
10]. Remarkably, no study has ever supported a risk association of autism with vaccines, and as shown in meta-analyses and systematic reviews [
9], the convergence of negative findings across investigators, study designs, samples and countries has been impressive. Further claims were made that the risk could be confined to a small, vulnerable, subgroup that epidemiological studies would not be capable to detect. Systematic search for this hypothetical subgroup (defined by regression, onset immediately after MMR shot, co-occurrence of gastrointestinal symptoms and inflammation, and abnormal persistence of measles virus in the gut wall) failed to validate its existence [
11–
13].
