a) Jabs can cause fever b) fever modulates austistic symptoms
"Fever is a frequent systemic adverse event following immunization, especially in infants and young children."
and from Albert Einstein College:
"The new theory stems from decades of anecdotal observations that some autistic children seem to improve when they have a fever, only to regress when the fever ebbs."
Vaccination and immunization may induce fever, which is usually fairly mild. There is much anecdotal evidence, confirmed by recent research, that fever can temporarily reduce autistic spectrum symptoms. Hence a parent who noticed autistic symptoms worsening as a vaccination-induced fever abated might not unreasonably blame this worsening on the vaccination/immunization. In such a situation there is indeed a correlation, though epidemiological studies of the MMR jab have shown that it does not cause autism.
Given big pharma's track record, it's hardly surprising that some will dig their heels in and call 'liar' when told that there is absolutely no connection at all. Some parents will have seen their child develop a fever following the jab; and seen the sutistic symptoms worsen as the fever diminished.
The myth that MMR causes autism will disapear only when it is widely realised that jabs sometimes cause a fever and that fever can modulate autistic spectrum symptoms.