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Objective. To assess the possible toxicity of thimerosal-containing vaccines (TCVs) among infants. Methods. A 2-phased retrospective cohort study was conducted using computerized health maintenance organization (HMO) databases. Phase I screened for associations between neurodevelopmental disorders and thimerosal exposure among 124 170 infants who were born during 1992 to 1999 at 2 HMOs (A and B). In phase II, the most common disorders associated with exposure in phase I were reevaluated among 16 717 children who were born during 1991 to 1997 in another HMO (C). Relative risks for neurodevelopmental disorders were calculated per increase of 12.5 [micro]g of estimated cumulative mercury exposure from TCVs in the first, third, and seventh months of life. Results. In phase I at HMO A, cumulative exposure at 3 months resulted in a significant positive association with tics (relative risk [RR]: 1.89; 95% confidence interval [CI]: 1.05-3.38). At HMO B, increased risks of language delay were found for cumulative exposure at 3 months (RR: 1.13; 95% CI: 1.01-1.27) and 7 months (RR: 1.07; 95% CI: 1.01-1.13). In phase II at HMO C, no significant associations were found. In no analyses were significant increased risks found for autism or attention-deficit disorder. Conclusions. No consistent significant associations were found between TCVs and neurodevelopmental outcomes. Conflicting results were found at different HMOs for certain outcomes. For resolving the conflicting findings, studies with uniform neurodevelopmental assessments of children with a range of cumulative thimerosal exposures are needed. Pediatrics 2003;112:1039-1048; cohort study, computerized medical record systems, language development disorders, speech disorders, thimerosal, vaccines., ABBREVIATIONS. Hg, mercury; EPA, Environmental Protection Agency; TCV, thimerosal-containing vaccine; HMO, health maintenance organization; VSD, Vaccine Safety Datalink; CDC, Centers for Disease Control and Prevention; LBW, low birth weight; ICD9-CM, [...]

Objective. Varicella breakthrough, the occurrence of varicella disease >42 days after vaccination, is indicative of vaccination failure. A sevenfold increased risk of breakthrough among vaccinated children with asthma was observed in a 1996 varicella out break in a child care center. More recent outbreak investigations have also identified age at vaccination as a potential risk factor for breakthrough. We assessed the association of varicella breakthrough with asthma, steroids, age at varicella vaccination, and timing of measles-mumps-rubella (MMR) vaccination. Methods. We performed a retrospective cohort study among children born after 1993 and followed up through 1999 at 2 health maintenance organizations ([HMOs] A and B) in the United States. Information was obtained from automated vaccination, clinic, hospital discharge, and pharmacy records. Results. We identified 268 and 97 breakthrough cases among 80 584 and 8181 children vaccinated against varicella at HMOs A and B, respectively. Varicella breakthrough was not associated with asthma, inhaled steroids prescribed at any time, and oral steroids prescribed before vaccination. An increased risk of varicella breakthrough was found in the 3 months immediately after prescription for oral steroids at HMO A (adjusted relative risk [aRR]: 2.4, 95% confidence interval [CI]: 1.3-4.4) and HMO B (aRR: 2.8; 95% CI: 1.0-7.8), when varicella vaccine was given before 15 months of age at HMO A (aRR: 1.4, 95% CI: 1.1-1.9), and when varicella vaccination followed MMR vaccine within 28 days at HMO A (aRR: 3.1, 95% CI: 1.5-6.4). Conclusions. Varicella vaccine failure in children was not associated with asthma or the use of inhaled steroids, but with the use of oral steroids. Administration of varicella vaccine before the age of 15 months may be associated with a slightly increased risk of breakthrough disease. As currently recommended, varicella vaccination should not be administered for 28 days after MMR vaccination. URL: http://www.pediatrics.org/cgi/content/full/112/2/e98; varicella vaccine, asthma, steroids, measles-mumps-rubella vaccine, chickenpox.

To the Editor.-- I am the first author of a recent article on a study undertaken by the Centers for Disease Control and Prevention (CDC) to screen for a potential [...]