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Does the MMR vaccine cause autism?

May 8, 2010 2 comments

The question of safety is the main vaccine concern. Are vaccines safe? If I vaccinate my child, will that have negative effects for their health? Of course, these questions are extremely broad to be answered all at once. Thus I will be breaking the answers in little bits. Today we will look at the MMR (Measles, Mumps & Rubella) vaccine and autism. Is the MMR vaccine correlated with autism? A quick PubMed search found this study from the June 12, 1999 Lancet (the same journal that originally published and recently retracted the Wakefield study that is widely credited with starting the MMR/vaccine hysteria):

Autism and measles, mumps, and rubella vaccine: no epidemiological evidence for a causal association.

Taylor B, Miller E, Farrington CP, Petropoulos MC, Favot-Mayaud I, Li J, Waight PA.

Department of Community Child Health, Royal Free and University College Medical School, University College London, UK

Study Summary: The authors looked at data about autism diagnoses since 1979 and data about MMR vaccinations, which started in 1988 in the UK, to try to see if there is any increase in autism diagnoses in or around the time when the MMR vaccine was introduced. They found that autism rates were steadily increasing every year and no “step-up” in autism diagnoses occurred when the vaccine was introduced, thus lending credibility to the conclusion that MMR does not seem to increase autism rates.

There was a steady increase in cases by year of birth with no sudden “step-up” or change in the trend line after the introduction of MMR vaccination. There was no difference in age at diagnosis between the cases vaccinated before or after 18 months of age and those never vaccinated. There was no temporal association between onset of autism within 1 or 2 years after vaccination with MMR (relative incidence compared with control period 0.94 [95% CI 0.60-1.47] and 1.09 [0.79-1.52]). Developmental regression was not clustered in the months after vaccination (relative incidence within 2 months and 4 months after MMR vaccination 0.92 [0.38-2.21] and 1.00 [0.52-1.95]). No significant temporal clustering for age at onset of parental concern was seen for cases of core autism or atypical autism with the exception of a single interval within 6 months of MMR vaccination. This appeared to be an artifact related to the difficulty of defining precisely the onset of symptoms in this disorder. INTERPRETATION: Our analyses do not support a causal association between MMR vaccine and autism. If such an association occurs, it is so rare that it could not be identified in this large regional sample.

Now, let us keep in mind that, one study never proves anything. At best one study points to a possible direction, no matter how well done, and how rock solid that one study may appear. What matters is the literature as a whole; what do all the studies done on the topic suggest. As such,  given that this is the first study about vaccines & autism we’ve reviewed here, let us not interpret this as proof that the MMR vaccine is not correlated to autism. Only when we have found more studies, and only when all the studies appear to reach the same conclusion can we say with any level of certainty that it appears highly unlikely that the MMR vaccines causes an increase in autism levels.

New Genetic Clues to Autism Found


READ THE REST OF THIS ARTICLE AT WEBMD

May 3, 2010 — Researchers have discovered two new genes that may be involved with autism, the brain disorder marked by difficulty in communicating and relating to others.

The evidence for one of the two new “susceptibility genes” is stronger than that for the other, says Daniel Notterman, MD, the senior author of the study and a professor of pediatrics, biochemistry, and molecular biology at Penn State College of Medicine in Hershey.

One of the newly discovered gene mutations is in NCAM2 and the other is in PTPRD.

“We are more confident about NCAM2 and less about PTPRD,” Notterman tells WebMD.

The researchers announced the discovery Sunday at the Pediatric Academic Societies annual meeting in Vancouver, British Columbia.

Autism or autism spectrum disorder, involving less severe forms of the condition, affect one in 110 U.S. children, according to estimates from the CDC.

The new finding, Notterman says, adds to the growing evidence for genetic links for autism but doesn’t rule out a role for environmental factors. “Over the last couple of years, beginning in 2007, it’s become clear that some cases of autism, maybe up to 15%, will be caused by rare mutations, either occurring spontaneously or that can be inherited by a parent,” he says.

Tracking the Autism Genes

Notterman and his colleagues analyzed data from the Autism Genetic Resource Exchange (AGRE), a collaborative gene bank for autism, on  943 families, most of whom had more than one child diagnosed with autism. In all, they evaluated  3,742 family members.

They compared these with genetic data from 6,317 people without developmental or neuropsychiatric conditions.

Comparing genetic information on those affected with autism and those not, Notterman says, ”gave us a starting list of about 25 genetic mutations” found more commonly in those with autism.

Next, the researchers looked at whether the 25 were substantially different in the two groups, and in the process narrowed the list of suspect genes to four.

Two of the four had already been identified by researchers as linked with autism. The other two were new. “No one had shown this [link] statistically,” Notterman says.

READ THE REST OF THIS ARTICLE AT WEBMD

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