evidence: The GACVS reviewed 2 published papers alleging that aluminium in vaccines is associated with autism spectrum disorders3, 4 and the evidence generated from quantitative risk assessment by a US FDA pharmacokinetic model of aluminium-containing vaccines. GACVS considers that these 2 studies3, 4 are seriously flawed. The core argument made in these studies is based on ecological comparisons of aluminium content in vaccines and rates of autism spectrum disorders in several countries. In general, ecological studies cannot be used to assert a causal association because they do not link exposure to outcome in individuals, and only make correlations of exposure and outcomes on population averages. Therefore their value is primarily for hypothesis generation. However, there are additional concerns with those studies that limit any potential value for hypothesis generation. These include: incorrect assumptions about known associations of aluminium with neurological disease, uncertainty of the accuracy of the autism spectrum disorder prevalence rates in different countries, and accuracy of vaccination schedules and resulting calculations of aluminium doses in different countries. [...] 3Tomljenovic L, Shaw CA. Do aluminum vaccine adjuvants contribute to the rising prevalence of autism? Journal of Inorganic Biochemistry, 2011; 105: 1489–1499.