A new study has struck another blow in the ongoing battle over the supposed link between childhood vaccinations and autism spectrum disorders. This debate started in earnest in 1998 after a study published in the British journal Lancet linked the common MMR (measles, mumps, rubella) vaccine to the subsequent development of physical symptoms resembling autism. The study is still often cited by those calling for further government action on the matter, but it only linked the two variables in an indirect way, noting that gastrointestinal (GI) problems common to the 12 vaccinated infants involved in the study were similar to those seen in many autistic cases and that traces of the vaccinations were supposedly responsible. That single study provoked a controversy whose influence has been so great that current presidential candidate John McCain nearly stated its assertions as fact in February.

The ostensible purpose of the newly published study, led by researchers from Columbia University, Massachusetts General Hospital and the Centers for Disease Control (CDC), was to recreate the Lancet research and compare results – they even invited one of the co-authors of the original study to participate in the new one. The two papers’ conclusions, however, do not match. Like most vaccines, the MMR inoculates young children by exposing them to the viruses. Lancet researchers reportedly found trace evidence of the measles virus in subjects affected by both autism and gastrointestinal issues. They speculated that these traces of the virus remained in the bodies of these infants and that the correspondingly overworked immune systems caused the bowels to leak, allowing the virus to migrate to the brain and create developmental problems amounting to autism. The CDC study used identical parameters to examine a group of children, average 5 years of age, who had GI problems. Most were also autistic. But unlike the Lancet team, CDC researchers found traces of the virus in only two of the children, one of whom was autistic and one of whom was not. They also noted that all but 5 of the children in the study reported GI symptoms before receiving the vaccination.

The results were replicated three times in three different labs, proving that the MMR vaccine did not cause either GI or autism in the subject sample. This new study has effectively cancelled out the original research, but thousands will continue to see both a link between the vaccine and the incidence of autism spectrum disorders and a malicious intent on the part of national health care organizations. In some cases, adverse reactions to vaccines may indeed provoke developmental disorders. But the epidemic noted in conspiracy literature simply does not exist, and the medical consensus remains unchanged. The risks inherent in these vaccinations are far smaller than the risks that children run by exposing themselves to the common diseases they prevent.

Measles rates remain low in the developed world, but they have recently begun to rise in Britain and the United States, where vaccination rates dropped in the last decade primarily because of the Lancet controversy. The fact is that autism rates will almost certainly continue to rise as we refine our definition of the spectrum. But without vaccination, avoidable childhood diseases will grow more common as well. The ridiculously slight chance that a child’s development will be compromised by these doses is very easily cancelled out by the protection that they provide. Of course, the study concerned only the MMR vaccine, and a majority of skeptics remain unconvinced. The controversy will continue.