RÉSUMÉ
Epidemiological evidence suggests a link between mercury [Hg] exposure from Thimerosal-containing vaccines and specific delays in development. A hypothesis-testing longitudinal cohort study [n = 49,835] using medical records in the vaccine Safety Datalink [VSD] was undertaken to evaluate the relationship between exposure to Hg from Thimerosal-containing hepatitis B vaccines [T-HBVs] administered at specific intervals in the first 6 months of life and specific delays in development [International Classification of Disease, 9th revision [ICD-9]: 315.xx] among children born between 1991 and 1994 and continuously enrolled from birth for at least 5.81 years. Infants receiving increased Hg doses from T-HBVs administered within the first month, the first 2 months, and the first 6 months of life were significantly more likely to be diagnosed with specific delays in development than infants receiving no Hg doses from T-HBVs. During the decade in which T-HBVs were routinely recommended and administered to US infants [1991-2001] an estimated 0.5-1 million additional US children were diagnosed with specific delays in development as a consequence of 25 jig or 37.5jig organic Hg from T-HBVs administered within the first 6 months of life. The resulting lifetime costs to the United States may exceed $1 trillion