Aunque la evidencia epidemiológica no ha apoyado la hipótesis de una relación causal entre las vacunas y el autismo que contienen timerosal, las preocupaciones continúan sobre la exposición infantil al mercurio a través de la administración de la vacuna. Un comunicado emitido por la Academia Americana de Pediatría y el Servicio de Salud Pública de los EE.UU., en 1999 llevó a la eliminación de timerosal de muchas vacunas. En 2004, el Comité de Revisión de Seguridad de la Inmunización del Instituto de Medicina rechazó la hipótesis de una relación causal entre las vacunas que contienen timerosal y el autismo.En una búsqueda en MEDLINE y EMBASE, se identificaron los artículos que abordan la posible asociación entre el timerosal y los trastornos del desarrollo neurológico, específicamente el autismo. En este artículo se revisan los últimos estudios de farmacocinética y epidemiológicos publicados entre 2003 y 2008 en relación con el enlace propuesto entre el timerosal y el autismo.

CONTEXTO: Los compuestos mercúricos son nefrotóxicos y neurotóxicos a dosis altas. El timerosal, un preservante muy utilizado en las formulaciones de vacunas, contiene etilmercurio, por lo que se ha sugerido que la vacunación infantil con vacunas que contienen timerosal podría estar relacionada causalmente con trastornos del neurodesarrollo como el autismo. OBJETIVO: Determinar si la vacunación con una vacuna que contiene timerosal está asociada con el desarrollo de autismo. DISEÑO, LUGAR Y PARTICIPANTES: Estudio poblacional de cohorte de todos los niños nacidos en Dinamarca entre el 1 de enero de 1990 y el 31 de diciembre de 1996 (N = 467 450) comparando niños vacunados con una vacuna que contiene timerosal con niños vacunados con una formulación libre de timerosal de la misma vacuna. PRINCIPALES MEDIDAS DE RESULTADO: El riesgo relatiovo (RR) para autismo y otros trastornos del espectro autista, incluyendo la tendencia observada en relación a la dosis de etilmercurio. RESULTADOS: Durante 2 986 654 personas-año, se identificaron 440 casos de autismo y 787 casos de otros trastornos del espectro autista. El riesgo de autismo y otros trastornos del espectro autista no difirió significativamente entre los niños vacunados con vacunas que contienen timerosal y los niños vacunados con la vacuna sin timerosal (RR 0,85 [95% intervalo de confianza [IC] de 0,60 a 1,20] para autismo; RR 1,12 [IC del 95% de 0,88 a 1,43] para otros trastornos del espectro autista). Por otra parte, no se encontraron pruebas de una asociación dosis-respuesta (aumento en el RR por cada 25 microgramos de etilmercurio, 0,98 [IC del 95% de 0,90 a 1,06] para el autismo y 1,03 [IC del 95% de 0,98 a 1,09] para otros trastornos del espectro autista). CONCLUSIÓN: Los resultados no apoyan una relación causal entre la vacunación infantil con vacunas que contienen timerosal y el desarrollo de trastornos del espectro autista.

Ha habido una enorme debate sobre la posibilidad de una relación entre las vacunas infantiles y el posterior desarrollo de autismo. Esto en los últimos tiempos se ha convertido en un importante problema de salud pública con el aumento de las enfermedades prevenibles por vacunación en la comunidad debido al temor de un "vínculo" entre las vacunas y el autismo. Se realizó un metanálisis para resumir la evidencia disponible de estudios de casos y controles y de cohortes sobre este tema (MEDLINE, PubMed, EMBASE, Google Académico hasta abril de 2014). Los estudios elegibles evaluaron la relación entre la administración de la vacuna y el posterior desarrollo de autismo o de Trastornos del Espectro Autista (TEA). Dos revisores extrajeron los datos sobre las características del estudio, métodos y resultados. Los desacuerdos se resolvieron por consenso con otro autor. Cinco estudios de cohortes en 1.256.407 niños, y cinco estudios de casos y controles que iinvolucraron 9.920 niños fueron incluidos en este análisis. Los datos de cohortes no revelaron ninguna relación entre la vacuna y el autismo (OR: 0,99; IC del 95%: 0,92 a 1,06) o ASD (OR: 0,91; IC del 95%: 0,68 a 1,20), ni hubo una relación entre el autismo y MMR (OR : 0,84; IC del 95%: 0,70 a 1,01), o timerosal (OR: 1,00; IC del 95%: 0,77 a 1,31), o el mercurio (Hg) (OR: 1,00; IC del 95%: 0,93 a 1,07). Del mismo modo los datos de casos y controles no encontraron evidencia de un mayor riesgo de desarrollar autismo o TEA seguido de MMR, Hg, o la exposición al timerosal cuando se agrupan por la condición (OR: 0,90; IC del 95%: 0,83 a 0,98; p = 0,02) o agrupadas por el tipo de exposición (OR: 0,85; IC del 95%: 0,76 a 0,95; p = 0,01). Los resultados de este meta-análisis sugieren que las vacunas no están asociados con el desarrollo de autismo o trastornos del espectro autista . Además, los componentes de las vacunas (timerosal o mercurio) o múltiples vacunas (MMR) no están asociados con el desarrollo de autismo o trastorno del espectro autista.

In Poland, administered childhood vaccines still contain thimerosal as a preservative. Despite the access to mercury free formulas, the most of children are still vaccinated by thimerosal-containing vaccines (TCV) owing to economical reasons. That circumstances caused the rising discussion on potential harmful influence of TCVs on children health. The objective of this analysis was to determine an association of TCVs exposure with the risk of autism. Study population included 96 cases diagnosed with childhood or atypical autism and 192 controls matched individually by year of birth, gender, and physician's practice. Data on autism diagnose and vaccination history were from GPs. Data on the other possible autism risk factors were collected from mothers. Conditional logistic regression was used to assess the risk of autism due to TCVs exposure. No significant association was found between TCVs exposure and autism. After adjusting to potential confounders, odds ratios of the risk of autism developing for infants vaccinated with TCVs were 1.52 (95% CI: 0.29-11.11) for doses 12.5-87.5 microg, 2.78 (95% CI: 0.29-11.11) for 100-137.5 microg and 1.97 (95% CI: 0.37-18.95) for these exposed > or = 150 microg. Our study revealed no evidence of an association between TCVs and autism.

RECORD STATUS: None CITATION: Higgins S. The measles-mumps-rubella vaccine (MMR) and autism Clayton, Victoria: Centre for Clinical Effectiveness (CCE) 2003: 14

RECORD STATUS: None CITATION: Health Technology Advisory Committee. MMR vaccine and autism: no evidence of association. Minnesota: Health Technology Advisory Committee (HTAC) 2001

BACKGROUND: In 1999, concerns were raised that vaccines containing the preservative Thimerosal might increase the risk of autism and/or other neurodevelopmental disorders. METHODS: Between the mid-1980s through the late-1990s, we compared the prevalence/incidence of autism in California, Sweden, and Denmark with average exposures to Thimerosal-containing vaccines. Graphic ecologic analyses were used to examine population-based data from the United States (national immunization coverage surveys and counts of children diagnosed with autism-like disorders seeking special education services in California); Sweden (national inpatient data on autism cases, national vaccination coverage levels, and information on use of all vaccines and vaccine-specific amounts of Thimerosal); and Denmark (national registry of inpatient/outpatient-diagnosed autism cases, national vaccination coverage levels, and information on use of all vaccines and vaccine-specific amounts of Thimerosal). RESULTS: In all three countries, the incidence and prevalence of autism-like disorders began to rise in the 1985-1989 period, and the rate of increase accelerated in the early 1990s. However, in contrast to the situation in the United States, where the average Thimerosal dose from vaccines increased throughout the 1990s, Thimerosal exposures from vaccines in both Sweden and Denmark-already low throughout the 1970s and 1980s-began to decrease in the late 1980s and were eliminated in the early 1990s. CONCLUSIONS: The body of existing data, including the ecologic data presented herein, is not consistent with the hypothesis that increased exposure to Thimerosal-containing vaccines is responsible for the apparent increase in the rates of autism in young children being observed worldwide.

OBJECTIVE: Exposure to thimerosal, a mercury-containing preservative that is used in vaccines and immunoglobulin preparations, has been hypothesized to be associated with increased risk of autism spectrum disorder (ASD). This study was designed to examine relationships between prenatal and infant ethylmercury exposure from thimerosal-containing vaccines and/or immunoglobulin preparations and ASD and 2 ASD subcategories: autistic disorder (AD) and ASD with regression. METHODS: A case-control study was conducted in 3 managed care organizations (MCOs) of 256 children with ASD and 752 controls matched by birth year, gender, and MCO. ASD diagnoses were validated through standardized in-person evaluations. Exposure to thimerosal in vaccines and immunoglobulin preparations was determined from electronic immunization registries, medical charts, and parent interviews. Information on potential confounding factors was obtained from the interviews and medical charts. We used conditional logistic regression to assess associations between ASD, AD, and ASD with regression and exposure to ethylmercury during prenatal, birth-to-1 month, birth-to-7-month, and birth-to-20-month periods. RESULTS: There were no findings of increased risk for any of the 3 ASD outcomes. The adjusted odds ratios (95% confidence intervals) for ASD associated with a 2-SD increase in ethylmercury exposure were 1.12 (0.83-1.51) for prenatal exposure, 0.88 (0.62-1.26) for exposure from birth to 1 month, 0.60 (0.36-0.99) for exposure from birth to 7 months, and 0.60 (0.32-0.97) for exposure from birth to 20 months. CONCLUSIONS: In our study of MCO members, prenatal and early-life exposure to ethylmercury from thimerosal-containing vaccines and immunoglobulin preparations was not related to increased risk of ASDs.

BACKGROUND: The purpose of the study was to evaluate the effects of MMR immunization and mercury from thimerosal-containing childhood vaccines on the prevalence of autism. MATERIAL/METHODS: Evaluations of the Biological Surveillance Summaries of the Centers for Disease Control and Prevention (CDC), the U.S. Department of Education datasets, and the CDC's yearly live birth estimates were undertaken RESULTS: It was determined that there was a close correlation between mercury doses from thimerosal--containing childhood vaccines and the prevalence of autism from the late 1980s through the mid-1990s. In contrast, there was a potential correlation between the number of primary pediatric measles-containing vaccines administered and the prevalence of autism during the 1980s. In addition, it was found that there were statistically significant odds ratios for the development of autism following increasing doses of mercury from thimerosal-containing vaccines (birth cohorts: 1985 and 1990-1995) in comparison to a baseline measurement (birth cohort: 1984). The contribution of thimerosal from childhood vaccines (>50% effect) was greater than MMR vaccine on the prevalence of autism observed in this study. CONCLUSIONS: The results of this study agree with a number of previously published studies. These studies have shown that there is biological plausibility and epidemiological evidence showing a direct relationship between increasing doses of mercury from thimerosal-containing vaccines and neurodevelopmental disorders, and measles-containing vaccines and serious neurological disorders. It is recommended that thimerosal be removed from all vaccines, and additional research be undertaken to produce a MMR vaccine with an improved safety profile.

OBJECTIVE: The first objective of the study was to determine whether there is a relationship between the measles-mumps-rubella (MMR) vaccination and autism in children. The second objective was to examine whether the risk of autism differs between use of MMR and the single measles vaccine. DESIGN: Case-control study. STUDY POPULATION: The 96 cases with childhood or atypical autism, aged 2 to 15, were included into the study group. Controls consisted of 192 children individually matched to cases by year of birth, sex, and general practitioners. METHODS: Data on autism diagnosis and vaccination history were from physicians. Data on the other probable autism risk factors were collected from mothers. Logistic conditional regression was used to assess the risk of autism resulting from vaccination. Assessment was made for children vaccinated (1) Before diagnosis of autism, and (2) Before first symptoms of autism onset. Odds ratios were adjusted to mother's age, medication during pregnancy, gestation time, perinatal injury and Apgar score. RESULTS: For children vaccinated before diagnosis, autism risk was lower in children vaccinated with MMR than in the nonvaccinated (OR: 0.17, 95% CI: 0.06-0.52) as well as to vaccinated with single measles vaccine (OR: 0.44, 95% CI: 0.22-0.91). The risk for vaccinated versus nonvaccinated (independent of vaccine type) was 0.28 (95% CI: 0.10-0.76). The risk connected with being vaccinated before onset of first symptoms was significantly lower only for MMR versus single vaccine (OR: 0.47, 95% CI: 0.22-0.99). CONCLUSIONS: The study provides evidence against the association of autism with either MMR or a single measles vaccine.