Research on Vaccine Safety- Page 2 of 2

A study found that thimerosal and MMR vaccine were not linked to prevalence of pervasive developmental disorders in 28,000 children in Montreal, Quebec, Canada, born between 1987-1998 (including 180 identified with a pervasive developmental disorder). Data ruled out an association between pervasive developmental disorder and either high levels of ethyl mercury exposure or 1- or 2-dose MMR vaccinations.

A study of 467,000 children born in Denmark between 1990 and 1996 compared children who were vaccinated with a thimerosal-containing vaccine to children who received a thimerosal-free formulation of the same vaccine. The risk of autism spectrum disorders did not differ significantly between children vaccinated with thimerosal-containing vaccine and children vaccinated with thimerosal-free vaccine. The results do not support a causal relationship between childhood vaccination with thimerosal-containing vaccines and development of autism spectrum disorders.

Researchers monitored the thimerosal exposure of more than 14,000 children born in the United Kingdom between 1991 and 1992. The age at which doses of thimerosal-containing vaccines were administered was recorded, and measures of mercury exposure by 3, 4 and 6 months of age were calculated and compared with numerous measures of childhood cognitive and behavioral development between 6 and 91 months of age. No evidence was found that early exposure to thimerosal had a negative effect on neurologic or psychological outcomes.

Data were analyzed from the Danish Psychiatric Central Research Register recording all psychiatric admissions since 1971, and all outpatient contacts in psychiatric departments in Denmark since 1995. There was no trend toward an increase in the incidence of autism during the period when thimerosal was used in Denmark through 1990. From 1991-2000, the incidence increased and continued to rise after thimerosal was removed from vaccines. There also were increases among children born after thimerosal was no longer used. Data do not support a correlation between thimerosal-containing vaccines and the incidence of autism.

A study compared the prevalence and incidence of autism in California, Sweden and Denmark from the mid-1980s to the late 1990s with average exposures to thimerosal-containing vaccines. In all three locations, the incidence and prevalence of autism spectrum disorders began to rise in the 1985-1989 period, and the rate of increase accelerated in the early 1990s. In California, the average thimerosal dose from vaccines increased throughout the 1990s. In Sweden and Denmark, exposure to thimerosal from vaccines was low during the 1970s and 1980s, decreased in the late 1980s and was eliminated in the early 1990s. The data do not support the theory that increased exposure to thimerosal-containing vaccines is responsible for the apparent increase in the rates of autism in young children being observed worldwide.

A study analyzed thimerosal exposure and possible developmental delay in 109,863 children born in the UK from 1988 to 1997. Exposure was defined according to the number of diphtheria-tetanus-pertussis/diphtheria-tetanus (DTP/DT) doses received by 3 and 4 months of age, as well as the cumulative age-specific DTP/DT exposure by 6 months of age. With the possible exception of tics, there was no evidence that thimerosal exposure via DTP/DT vaccines causes neurodevelopmental disorders.

Researchers compared early exposure to mercury from thimerosal-containing vaccines and thimerosal-containing immune globulin to 42 neuropsychological outcomes in 1,047 children ranging in age from 7 to 10 years. Immune globulin is a substance used to boost the immune system in people with certain conditions. Exposure to mercury from thimerosal was determined from computerized immunization records, medical records, personal immunization records and parent interviews. The study did not support a causal association between early exposure to thimerosal used in vaccines and immune globulin and deficits in neuropsychological functioning at the age of 7 to 10 years.

Autism client data from the California Department of Developmental Services were analyzed between 1995-2007. Thimerosal was removed from recommended childhood vaccines after 2002, but autism cases continued to increase each quarter. The data do not show a decrease in autism in California even after trace levels of thimerosal were removed from nearly all childhood vaccines. Data did not support the hypothesis that exposure to thimerosal during childhood is a primary cause of autism.

Researchers reviewed managed care organization records and conducted interviews with the parents of 256 children with autism spectrum disorder (ASD). Another 752 children without autism, matched to the ASD children by birth year, gender and managed care organization, were also studied. Prenatal and early-life exposure to mercury from thimerosal-containing vaccines and immune globulin (a substance used to boost the immune system in people with certain conditions) was not related to increased risk of ASDs.