A new large-scale Danish study searches for connections between autism and the MMR vaccine. In particular, they investigate at-risk individuals. Once again, no links are found. Share on Pinterest The latest study to look at MMR vaccines and autism goes an extra step. The furor surrounding vaccines and their relationship with autism has been rumbling along for decades. A paper published in 1998 first described a link between the measles, mumps, and rubella (MMR) vaccine and autism. Both the findings and the lead researchers have since been entirely discredited. Anyone who takes an interest in science might be asking whether we need to carry out any more research in defense of the MMR jab. After all, strong evidence has already been collected, confirmed, and replicated.

Facts upon facts The author of the study that sparked the storm, Andrew Wakefield, has since been stripped of his clinical and academic credentials. Vaccination rates dropped after the panic began, and they still have not returned to the levels needed to protect children from disease adequately. The authors of the latest study write that “Measles outbreaks are not uncommon in Europe and in the United States, and vaccine hesitancy or avoidance has been identified as a major cause.” Clearly, not everyone is convinced that the MMR vaccine is safe; scare stories are difficult to forget and worryingly easy to perpetuate. By continuing to publish high-quality evidence, the fears surrounding vaccines might, one day, be extinguished once and for all.

Overturning all arguments Some people have criticized earlier studies that found no link between the MMR vaccine and autism. They argue that, although the vaccine might not increase autism risk at a population level, it might make a difference for children who already have an increased risk of autism. According to the authors of the present study, another common argument is that the vaccine is “associated with a regressive form of autism, leading to a clustering of cases with onset shortly after MMR vaccination.” They argue that this time-sensitive interaction might not have been picked up in some of the previous work. The team of scientists set out to overturn these arguments. This week, they published their findings in the Annals of Internal Medicine. The researchers, from the Statens Serum Institut in Copenhagen, Denmark, took data from a Danish population registry. In all, they had access to data from 657,461 children; of these, 6,517 received an autism diagnosis during the 10-year follow-up.

The data are in, again The researchers compared autism rates in children who had received the MMR vaccination and compared them against children who had not had the jab. As expected, there was no increase in risk associated with the vaccination. Similarly, even in children with a higher risk of developing autism, the MMR vaccination made no difference. The autism risk factors that the team accounted for included having a sibling with an autism diagnosis, low birth weight, maternal age, paternal age, and smoking during pregnancy. The authors conclude: “[O]ur study does not support that MMR vaccination increases the risk for autism, triggers autism in susceptible children, or is associated with clustering of autism cases after vaccination.” In further analyses, they also looked for links between vaccinations other than MMR and autism; again, they found none. One of the study’s main strengths is the large number of individuals included in the analysis. As the authors write, the study’s size allowed them to conclude that “even minute increases in autism risk after MMR vaccination are unlikely.”