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You may have heard of a recent study published in JAMA that once again confirmed that the measles, mumps, and rubella (MMR) vaccine is not related to autism. I just met the author of the study at a recent meeting, and she told me that the study is evidently the number one most downloaded from JAMA. Ever.
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. That's the topic of this week's Healthcare Triage.

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Doctor Aaron Carroll: You may have heard of a recent study published in JAMA that once again confirmed that the measles, mumps, and rubella, or MMR vaccine is not related to autism. I just met the author of the study at a recent meeting, and she told me that it's evidently the number one most downloaded from JAMA. Ever.

The study's findings, widely covered in the media, are considered robust and important, but it might be time to question how much good continued research in this area is doing. That's the topic of this week's Healthcare Triage.

[intro]

The study is entitled "Autism Occurrence by MMR Vaccine Status Among US Children With Older Siblings With and Without Autism," and it involved a cohort of about a hundred thousand children. They followed all of the kids from birth until they were at least 5 years old. The researchers were most interested in whether use of the MMR vaccine was associated with an increased risk of developing autism spectrum disorder, or ASD, especially in children at higher risk for the disorder by virtue of having a sibling with ASD. In the study, about 3,000 kids either had autism spectrum disorder, or had a sibling who did, which would place them at high risk. No association was found between the vaccine and ASDs, even for the kids at high risk. The conclusion: the MMR vaccine does not cause autism.

Look, the study has excellent methods, and its results are definitely robust, and I don't doubt that the findings were likely welcome to readers of JAMA and viewers of Healthcare Triage, as they provide confirmation that science, on top of decades of experience, confirms what we know to be true: the MMR vaccine is safe and effective.

Here's the thing: I'm starting to worry that our continued focus on the vaccine and autism issue is a distraction. It might be doing more harm than good. Can we all just agree that if this issue isn't decided yet in the minds of some people, it's never going to be put to rest? This is one of the most researched topics in medicine, ever.

As I noted in our episode on vaccines and autism, the most recent Cochrane review of research on the MMR vaccine included 5 randomized controlled 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. Anyone who looks at this overwhelming body of evidence and then calls for more research almost has to either be in denial of what the research shows, or be hoping that just one more trial might give a different result. But as you remember from our episode on Bayes' Theorem, our pre-study probability is so small and has so much evidence behind it that at this point, a much smaller study that found an association really shouldn't make us change our minds.

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 alters 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. Plus, even though everyone pretty much agrees that we should try to achieve the highest possible vaccination rates, things aren't as dire as the media sometimes makes it seem. Even in California, where the last big outbreak started, more than 92% of kindergartners had received 2 doses of the MMR vaccine. Only 3% had received exemptions from their schools system. That's not that bad.

It's also unclear whether those who oppose vaccination would be swayed by any more research. There's a lot of studies that show that when we're confronted by information that runs counter to our beliefs, we often become more entrenched, not less. In a study published in Pediatrics last year, political scientist and my upshot colleague Brendan Nyhan 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 these led to parents increasing their intent to vaccinate their children. None. They don't seem to work.

A few months later, Brendan published another study in the journal Vaccine; we covered that study in Healthcare Triage News, but it bears reviewing. In that work, he and a colleague attempted to correct misinformation about the influenza vaccine. Specifically, they tried to get people not believe in the myth that the flu shot can cause the flu, and 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. More information backfired.

There's a reasonably strong body of literature confirming that entrenched beliefs in myths are hard to shake. You may remember a political candidate who falsely claimed that the affordable care act would create "death panels." Well, a 2013 study found that strong supporters of this candidate were even more likely to believe death panels were real--after reading an article explaining that the claim wasn't true. I wrote an editorial on that study for the journal if you're interested, entitled "Combating Myths is Harder Than You Think."

Our unrelenting need to correct publicly 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, studies show 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. Is is possible-- 'cause research shows it-- to identify parents who are hesitant about vaccines. It's also possible-- again, proven by research-- to alter the ways that we talk to parents to make them more likely to change their minds. What probably won't help is another scientific study that shows that the MMR vaccine isn't associated with autism.

The facts, unfortunately, don't seem likely to make a difference among those who believe that the vaccine is unsafe. Maybe instead, we should focus on research exploring what actually does cause autism and what we should do to help kids who have it once it's diagnosed.

Healthcare Triage is supported in part by viewers like you through Patreon.com, a service that allows you to support the show through a monthly donation. We'd especially like to thank our honorary research associates: Cameron Alexander and Qadeem Salehmohamed. Thanks Cameron and Qadeem! If you'd like to support the show, more information can be found at patreon.com/healthcaretriage.