The title of this post is the same as that of a paper published in the Annals of Internal Medicine this month. I’ve added a comma before and in the interest of stylistic nicety. Twenty years ago a fraudulent paper was published in the Lancet which purported to link the MMR vaccine with autism. There was no reason prior to this paper to support such a connection and there has been none since. Nevertheless, people still worried that there might really be a cause and effect relationship to the extent that they didn’t allow their children to be vaccinated. The predictable result has been a resurgence in measles outbreaks. Measles is a serious disease that can cause serious sequelae or even death. Mumps and rubella also have major consequences, especially in adults, that can be prevented by vaccination.
A group from Denmark evaluated “whether the MMR vaccine increases the risk for autism in children, subgroups of children, or time periods after vaccination.” They studied “657 461 children born in Denmark from 1999 through 31 December 2010, with follow-up from 1 year of age and through 31 August 2013. During 5 025 754 person-years of follow-up, 6517 children were diagnosed with autism (incidence rate, 129.7 per 100 000 person-years). Comparing MMR-vaccinated with MMR-unvaccinated children yielded a fully adjusted autism hazard ratio of 0.93 (95% CI, 0.85 to 1.02). Similarly, no increased risk for autism after MMR vaccination was consistently observed in subgroups of children defined according to sibling history of autism, autism risk factors (based on a disease risk score) or other childhood vaccinations, or during specified time periods after vaccination. ”
Their conclusion was that their “study strongly supports that MMR vaccination does not increase the risk for autism, does not trigger autism in susceptible children, and is not associated with clustering of autism cases after vaccination. It adds to previous studies through significant additional statistical power and by addressing hypotheses of susceptible subgroups and clustering of cases.”
The study’s data are summarized in the table below. Click on it to enlarge it.
The above chart compares the likelihood of developing autism if vaccinated vs unvaccinated children. A hazard ratio (95% confidence interval) that straddles zero is statistically insignificant. As can be seen, none of the characteristics depicted on the chart were statistically different between vaccinated and unvaccinated subjects. There was one exception. Females had a hazard ratio of 0.79 with an interval of (0.64-0.97). This spread indicates that vaccinated females were less likely to develop autism than their unvaccinated counterparts. The authors of the study make little of this finding and it may be just a sport. No one is about to argue that vaccination reduces the propensity of children to be autistic.
The importance of this work is that it should put finis to the view still held by some parents that they are protecting their children by refusing to have them receive the MMR vaccine. There is no scientific reason to still hold that there is any association between this vaccine and autism. Is the vaccine free of side effects? Of course not, no treatment that works is devoid of unwanted outcomes. But the risk benefit ratio of the MMR vaccine is so favorable that all children should receive it. Their parents should be assured that allowing their children this preventative treatment is overwhelmingly more likely to have a benefit than it is to cause harm.