Does the MMR Vaccine cause autism?
The following is edited for length and re-printed from the Centers for Disease Control’s (CDC’s) website with permission, at http://www.cdc.gov/vaccinesafety
Current scientific evidence does not support the hypothesis that MMR vaccine, or any combination of vaccines, causes the development of autism, including regressive forms of autism. Epidemiologic studies have shown no relationship between MMR vaccination in children and development of autism. Taylor et al. (1999) studied 498 children with autism in the UK and found that the age at which they were diagnosed was the same regardless of whether they received the MMR vaccine before or after 18 months of age or whether they were never vaccinated. Importantly, no clustering of developmental regression was found after vaccination. Also, there was no "step up" in cases of autism or change in the trend line after introduction of MMR vaccine. Gillberg and Heijbel (1998) compared the prevalence of autism in children born in Sweden from 1975-1984. There was no difference in the prevalence of autism among children born before the introduction and after the introduction of the MMR vaccine. A recent study (Kaye et al., 2001) assessed the relationship between the risk of autism among children in the UK and MMR vaccine. Among a subgroup of boys aged 2-5 years, the risk of autism increased almost 4 fold from 1988 to 1993, while MMR vaccination coverage remained constant at approximately 95% over these same years. Similarly, among children born in 1980 to 1994 and enrolled in California kindergartens, there was a 373% relative increase in autism cases, though the relative increase in MMR vaccine coverage by the age of 24 months was only 14% (Dales et al., 2001). These data do not support a causal relationship between MMR vaccination and risk of autism. In 1999, the British Committee on Safety of Medicines convened a "Working Party on MMR Vaccine" to conduct a systematic review of reports of autism, gastrointestinal disease, and similar disorders after receipt of MMR or measles/rubella vaccine. It was concluded that the available information did not support the posited associations between MMR and autism and other disorders. In addition, in 1997, the National Childhood Encephalopathy Study (NCES) was examined to see if there was any link between measles vaccine and neurological events. The researchers found no indication that measles vaccine contributes to the development of long-term neurological damage, including educational and behavioral deficits (Miller et al., 1997).
What about other studies that suggest there might be a connection between autism and MMR vaccine?
Current scientific evidence does not support the hypothesis put forth by Wakefield and colleagues (1998) that the MMR vaccine causes the development of autism, including regressive forms of autism.Wakefield et al. (1998) reviewed reports of 12 children with bowel disease and regressive developmental disorders, mostly autism. In 9 of the cases, the child's parents or pediatrician speculated that the MMR vaccine had contributed to the behavioral problems of the children in the study. This was the only evidence suggesting a possible link with vaccination. An expert committee from the UK Medical Research Council (MRC) reviewed this study. The Council concluded there is no evidence to link the MMR vaccine with autism. On April 3, 2000 the MRC issued a new report confirming its earlier conclusion; MMR has not been linked with inflammatory bowel disease or autism. A copy of this report can be found at the MRC web site, http://www.mrc.ac.uk
What about the claim that the numbers of children with autism have been increasing ever since the MMR vaccine has been in use?
The data from California (Department. of Developmental Services, 1999) used to illustrate an increase in cases of autism were presented inaccurately (Fombonne, 2001). Fombonne (2001) lists several reasons why the data are misrepresented, for instance: 1) the figures presented are based on numbers, not rates, and do not account for population growth and changes in the composition of the population, 2) changes in diagnostic definitions were not controlled in the report, and 3) as in other areas of the country, children with autism are currently being diagnosed at earlier ages meaning that there will be an increase in the number of reported cases.
Should a younger sibling of an autistic child, or a child of someone who has autism be vaccinated with MMR or other vaccines?
Yes. Current scientific evidence does not show that MMR vaccine, or any combination of vaccines, causes the development of autism, including regressive forms of autism.A younger sibling or the child of someone who suffered a vaccine side effect usually can, and should, safely receive the same vaccine. This is especially true since the large majority of side effects after vaccination are local reactions and fever, which do not represent a contraindication.
Should we delay vaccination until we know more about the negative effects of vaccines?
No. There is no convincing evidence that vaccines such as MMR cause long term health effects. On the other hand, we do know that people will become ill and some will die from the diseases this vaccine prevents. Discontinuing a vaccine program based on unproven theories would not be in anyone's best interest. Isolated reports about these vaccines causing long term health problems may sound alarming at first. However, careful review of the science reveals that these reports are isolated and not confirmed by scientifically sound research. Detailed medical reviews of health effects reported after receipt of vaccines have often proven to be unrelated to vaccines, but rather have been related to other health factors. Because these vaccines are recommended widely to protect the health of the public, research on any serious hypotheses about their safety are important to pursue. Several studies are underway to investigate still unproven theories about vaccinations and severe side effects ("http://www.cdc.gov/vaccinesafety/Vaccines/MMR/index.html and http://www.cdc.gov/vaccinesafety/Concerns/thimerosal/thimerosal_faqs.html).
This article originally appeared in an issue of “Science in Autism Treatment”, the newsletter of the Association for Science in Autism Treatment (ASAT). It may not be republished or reprinted without advance permission from ASAT. For reprint permission please contact email@example.com