Just recently, a study published in JAMA once again confirmed that the measles, mumps, and rubella (MMR) vaccine is not related to autism. The study’s findings, widely covered in the media, are considered robust and important. But it may be time to question how much good continued research in this area is doing.
Aaron Carroll, MD, MS
This study examined a cohort of about 100 000 children, almost 3000 of whom developed autism spectrum disorder (ASD) or had an older sibling with the condition. They were followed from birth until at least 5 years of age. The main analysis examined whether use of the MMR vaccine was associated with an increased risk of developing ASD, especially in children at higher risk of the disorder by virtue of having a sibling with ASD.
No such association was found. The conclusion: the MMR vaccine does not cause autism.
This study was conducted using excellent methods and its results are robust. The findings were likely welcome to those of us who read JAMA, as they provide confirmation that science—in addition to many decades of experience—confirms what we know to be true: that the MMR vaccine is safe and effective.
The problem is that the continued focus on the vaccine and autism issue is a distraction. It also may be doing more harm than good.
Let’s start with the fact that if this issue isn’t “decided” yet in the minds of some people, it’s never going to be put to rest. The most recent Cochrane review of research on the MMR vaccine included 5 randomized clinical trials, 1 controlled trial, 27 cohort studies, 17 case-control studies, 5 time-series trials, 1 case cross-over trial, 2 ecological studies, and 6 self-controlled case series studies. These included data on almost 15 million children. No link could be found between vaccines and autism.
To continue to call for “more research” in the face of this body of evidence is either to be in denial of the findings or hoping that just 1 more trial might give a different result.
The reason to continue to perform work in this area is to add to our fund of knowledge in a way that informs, and potentially changes, practice. If a new study can’t change our beliefs, then it might not be worth doing. If it can’t change behavior, its importance is diminished further.
In addition, although many agree that we should try to achieve the highest possible vaccination rates, things are not as dire as the media might make it appear. Even in California, the focus of the latest outbreak, more than 92% of kindergarteners had received 2 doses of the MMR vaccine. Only 3% had received exemptions from the school system.
Furthermore, it’s not clear that those who oppose vaccination would be swayed by any more research. When confronted by information that runs counter to beliefs, people often become more entrenched in those ideas, not less.
In a study published in Pediatrics last year, political scientist Brendan Nyhan and colleagues tried 4 different interventions to increase parental acceptance of the MMR vaccine. These included factual information about MMR not causing autism; information about the dangers of measles, mumps, and rubella; pictures of kids with the diseases; and a dramatic narrative of a child who almost died of measles.
None of them led to parents increasing their intent to vaccinate their children.
A few months later, Nyhan published another manuscript in the journal Vaccine. In that study, he and a colleague attempted to correct misinformation about the influenza vaccine. Specifically, they were attempting to reduce belief in the myth that the flu shot can cause the flu. Although the intervention did reduce belief in the myth, it actually led to a reduced intent to get vaccinated among people who had high levels of concern about adverse effects of the vaccine. In this respect, more information backfired.
This backs up a reasonably strong body of literature confirming that entrenched beliefs in myths are hard to shake. A 2013 study found that strong supporters of a political candidate who falsely claimed the Affordable Care Act would create “death panels” were even more likely to believe death panels were real after reading an article explaining that the claim was not true.
Our unrelenting focus on correcting false notions about the MMR vaccine and autism may be doing more harm than good. Given that the risks of vaccine-preventable illnesses still remain low, empiric evidence shows that continuing to highlight the fact that people resist vaccines may be making exemptions more mainstream.
We absolutely should try to improve the vaccination of children. It is possible, as this study in JAMA Pediatrics shows, to identify parents who are hesitant about vaccines. It is also possible to alter the ways that we talk to parents to make them more likely to change their minds.
What likely won’t help is another scientific study finding that MMR is not associated with autism. The facts, unfortunately, aren’t likely to make a difference among those who believe the vaccine isn’t safe. Wouldn’t it be more productive to focus instead on research exploring what actually does cause autism and what we should do to help kids once it’s diagnosed?
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