Thursday, September 4, 2008

New data suggests MMR vaccine is NOT linked to autism

The MMR vaccine is not associated with autism, according to a new article published in the online scientific journal, PLOS. Scientists at the Mailman School of Public Health of Columbia University declared no link can be proven in their report.

The study provides more evidence against a link between the vaccine and autism than any in the past. As part of the research, the investigators replicated the 1988 study that detected a link and found nothing.

A case-control study was conducted looking at the timing of the onset of autism and gastrointestinal disorders, in relation to the vaccine.

The study also looked for the presence of measles in the bowel tissue of 25 cases and 13 controls.

Neither investigation supported the hypothesis that the measles component of the vaccine can lead to inflammation in the bowel and the release of neuroactive chemicals that promote developmental neuropathology.

If the hypothesis were true, the administration of the vaccine should precede the GI symptoms and the GI symptoms should precede the onset of autism. A cohort of 25 children with both autism and severe GI disorders was matched for age with 13 children with similar GI symptoms but not autism and the findings compared.

The median age of the autistic children and the control group was 5.5 and 5.1, respectively, and they got the first dose of MMR vaccine at about the same age, 15.3 versus 16 months.

The children were selected because their GI symptoms were sufficiently grave that a biopsy was indicated for clinical reasons, which allowed the researchers to obtain tissue samples for the current study and duplicate the original investigation in 1998 that raised the issue in The Lancet. That study reported the measles virus RNA in bowel tissue of 77% of children who had both autism and GI disorders, but not in children in a non-autistic control group.

Since then several studies have looked at the timing of the disorders and found no link between the vaccine and either autism or GI symptoms, but none has repeated the original investigation, until now.

In this study, using three different labs and modern molecular methods, the researchers found evidence of measles viral RNA in one case and one control, but otherwise they found no differences between the groups.

Equally, the temporal sequence of events did not support a link between the vaccine and either autism or GI disorders:

- The first appearance of GI symptoms averaged 12 months in the autism group and two in the controls.
- 13 of the 25 cases had the vaccine before the onset of autism.
- 16 of the cases had the GI symptoms before the onset of autism.
- And five of the cases had the vaccine before the onset of GI symptoms

The researchers were confident that the measles hypothesis is nullified, but added the finding doesn't rule out a link between autism and other vaccines, mercury compounds, PCBs, cell phones, or anything else.

Despite the concern over autism, the vaccine has shown itself to be safe and well tolerated, while significantly reducing the burden of disease, according to the CDC.

Data shows that the vaccine has been invaluable: before it was introduced in 1963, up to four million people were newly infected each year, up to 500 died, and 48,000 were hospitalized.

As of the end of July this year, the CDC had reports of 131 cases of measles in the U.S. (the highest number for the period since 1996), with 15 people, mostly young children, in the hospital and no deaths.


PLOS (open acccess, free download of article)

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