The claim that “vaccines cause autism” first received its scientific backing by Andrew Wakefield’s now-retracted study in The Lancet, published in 1998. The study’s authors examined 12 children, who were reported to have gastrointestinal problems and pervasive developmental disorder. Based on the results of this study, Wakefield claimed to have discovered a link between the measles, mumps and rubella (MMR) vaccine and autism. Although the number of children was too small to provide conclusive evidence, this story received wide and sensational media coverage, which led many parents to avoid vaccinating their children for fear of autism. This also set the stage for the rise of anti-vaccine groups and the fall in vaccine coverage of developed countries.

Apart from the flawed study, the fundamental problem with this hypothesis is that microbial infections – whether with bacteria, viruses or fungi – also result in immune activation. After all, this is part of how the immune system fights off infection. If it is true that simply activating the immune system results in autoimmune brain damage that causes autism, then autism rates in children would be much higher than they are. This is because common microbial infections (such as the cold) also happen to pregnant women and young children (the latter are a group notorious for frequent bouts of illness). In short, the hypothesis that “immune activation by aluminium adjuvants leads to autism-causing brain damage” is clearly unsupported by any evidence.

Anti-vaccine groups have also decried childhood vaccination schedules, in the belief that too many vaccines given in a short amount of time would “overwhelm” a child’s immune system and cause harmful effects. However, a study published in 2013 by DeStefano et al. using data from more than 200 children showed no increased risk of autism from increasing exposure to immune-stimulating agents in vaccines. An assessment of health outcomes from the US childhood vaccination schedule by the Institute of Medicine also found no evidence for concern. Nevertheless, this belief persists, and has led some parents to try to delay and “space out” the administration of different vaccines. As the American Association of Pediatricians has pointed out, children are exposed to far more immune-stimulating particles (also called antigens) on a daily basis than are harboured by all vaccines in the schedule. Spacing out vaccines only results in delayed protection, and a greater chance of contracting a vaccine-preventable disease and its complications.

Despite the complete lack of scientific evidence supporting the claim that vaccines cause autism – and a lot of evidence to the contrary – vaccine hesitancy remains a formidable obstacle to achieving optimal vaccine coverage. The idea that vaccines damage children’s brains is naturally a fearful prospect for parents, who have never seen first-hand the consequences of a vaccine-preventable disease. This fear has led to decreasing vaccination rates in the US and Europe, with predictable results. The consequent reduction in herd immunity has already resulted in measles outbreaks, notably in wealthy countries where vaccine access is not an issue:

• The US (New York and Washington)
• Europe (France, Italy)
• New Zealand (Canterbury, Auckland)
• Canada

https://healthfeedback.org/how-we-know-vaccines-do-not-cause-autism-why-this-belief-persists/