Autism and measles vaccine: no link found -- again
Suspicion that autism is triggered by childhood vaccinations -- notably the measles, mumps and rubella vaccine -- lingers on, even though studies repeatedly fail to find such a link. Another of those was published online today in the Public Library of Science ONE -- which allows full access after publication, so you can read the entire report here.
Led by scientists at the Columbia University Mailman School of Public Health, the research team took bowel tissue samples from 25 children with autism who had gut disturbances and compared it to bowel tissue of 11 children who also had such disturbances but did not have autism. The researchers screened the tissue for presence of the genetic material of the measles virus to see if the virus persisted more often in the children who had developed autism. Three labs examined the tissue independently, and no one knew which tissue came from autistic or non-autistic children until after the results were in. In all three labs, only two of the samples showed traces of the measles virus. One was from a child in the autism group and one was from a child without autism.
In other words, children with autism were no more likely to have measles virus in their tissue than ones who did not have autism, and that doesn't support a MMR-autism causal link, the authors concluded.
The scientists also investigated the temporal relationship you'd expect if the vaccine-autism theory were true. If the vaccine caused gut symptoms/autism, you'd expect the vaccine timing to precede either of the other two. This wasn't found.
Why did the researchers do this? The MMR-autism theory stems from a 1998 report by a British surgeon, Dr. Andrew Wakefield, that 12 children with autism and gastrointestinal disturbances had traces of the measles virus in their gut tissue. (The MMR vaccine uses a live, attenuated version of the measles virus.) Wakefield's theory was that the virus attacked the gut and caused autism. (Ten of the 13 authors of the paper, which was published in the Lancet, later retracted their authorship; you can read more about the Wakefield paper and subsequent controversy here and here.)
The researchers say they conducted the study because they saw a gap in the research that needed filling. Although many studies of populations have investigated whether kids who were vaccinated with MMR were more likely to develop autism than those who didn't -- and haven't found such a link -- no one since Wakefield has searched for the presence/absence of the viral RNA in children with autism.
Measles cases in the U.S. are at their highest rate in more than a decade, according to an August report from the Centers for Disease Control and Prevention -- a trend believed linked to vaccine fears.
But in related news, the CDC released data today reporting that vaccine rates for kids are high overall. "Childhood immunization rates remain at or near record levels, with at least 90% coverage for all but one of the individual vaccines in the recommended series for young children," the agency said. You can read all the estimates (which are from 2007) at the CDC website, as well as review the series of vaccines recommended for children. The one outlier: no, not MMR, but the last dose in a series of four for the diphtheria, tetanus and pertussis vaccine. Only 84.5% of U.S. children are estimated to have gotten that shot.
Finally, here's what some bloggers/organizations are saying about this latest MMR study (some links on this list shamelessly cribbed from the first one, Autism Vox -- many thanks!):
-- Rosie Mestel