Rationale for concern Thiomersal controversy

reports of autism cases per 1,000 children grew dramatically in u.s. 1996 2007. unknown how much, if any, growth came changes in autism s prevalence.

although intended increase public confidence in vaccinations, decision remove thiomersal instead led parents suspecting thiomersal cause of autism. concern on vaccine-autism link grew confluence of several underlying factors. first, methylmercury had decades been subject of widespread environmental , media concern after 2 highly publicized episodes of poisonings in 1950s , 1960s in minamata bay, japan industrial waste , in 1970s in iraq fungicide contamination of wheat. these incidents led new research on methylmercury safety , culminated in publication of array of confusing recommendations public health agencies in 1990s warning against methylmercury exposure in adults , pregnant women, ensured continued high public awareness of mercury toxicity. second, vaccine schedule infants expanded in 1990s include more vaccines, of which, including hib vaccine, dtap vaccine , hepatitis b vaccine, have contained thiomersal. third, number of diagnoses of autism grew in 1990s, leading parents of these children search explanation apparent rise in diagnoses, including considering possible environmental factors. dramatic increase in reported cases of autism during 1990s , 2000s largely attributable changes in diagnostic practices, referral patterns, availability of services, age @ diagnosis, , public awareness, , unknown whether autism s true prevalence increased during period. nevertheless, parents believed there growing autism epidemic , connected these 3 factors conclude increase in number of vaccines, , mercury in thiomersal in vaccines, causing dramatic increase in incidence of autism. advocates of thiomersal-autism link relied on indirect evidence scientific literature, including analogy neurotoxic effects of other mercury compounds, reported epidemiologic association between autism , vaccine use, , extrapolation in vitro experiments , animal studies studies conducted mark geier , son david geier have been cited research parents advocating link between thiomersal , autism. research geier has received considerable criticism methodological problems in research, including not presenting methods , statistical analyses others verification, improperly analyzing data taken vaccine adverse event reporting system, either mislabelling or confusing fundamental statistical terms in papers, leading results uninterpretable .