Thursday, October 22, 2009

Happy to Vaccinate

Generally I'm all about agreeing to disagree when it comes to someone else's parenting choices. After all, what you choose to do to your kid usually begins and ends inside your house, and while I might have an opinion, it doesn't directly affect me and mine. But that's not the case with vaccination, and that's part of why there's such a bitter debate about it. Anti-vax people feel oppressed by regulations and pressured, sometimes bullied and terrified, by doctors. Pro-vax people feel betrayed by members of their communities whose refusal to vaccinate reduces the herd immunity and puts everybody -- even the vaccinated -- at risk.

I should say up front that I am squarely, adamantly in the camp of the vaccinators. But I'm not without sympathy for the members of the other camp. I'm by nature a skeptic, and the healthcare industry deserves major skepticism. I am also, like many anti-vax-ers, a buyer of organic foods and eschewer of nasty chemicals. I treat colds with herb tea and bed rest. I clean with vinegar or baking soda. I don't love the idea of injecting my toddler with a passel of chemicals I can't spell -- it goes against a lot of my better instincts as a parent.

But here's the thing: there's a lot of good science on the side of vaccination, and opposing it is one flawed if not downright dirty study, a lot of anedote, and a lot of straight-up ignorance.

Most of the recent fear of vaccination comes from a study led by Andrew Wakefield and published in the British medical journal The Lancet in 1998. It purported to show a link between the MMR (measles mumps rubella) vaccine and autism. The study followed only 12 children -- a head-scratchingly small sample size -- and made only modest claims of correlation in 8 of those children. But even though 10 of the 13 co-authors of the Lancet article formally withdrew their findings, even though the study has been thoroughly discredited, and most importantly, even though considerable subsequent research has been unable to find a link between the MMR vaccine and autism spectrum disorder (ASD), people are still freaked out about vaccination.

Part of the reason is that there's a lot of anecdotal evidence of correlation between vaccines and the onset of autism. What happens is a kid gets a shot, and the next day, or maybe an hour later, or maybe a week later, he begins showing the first symptoms of ASD. Now, it's completely understandable that the adults in this child's life draw a line between the jab and the symptom, but it's not necessarily scientifically significant. Correlation is not causation. Just because two things happen in temporal proximity doesn't mean that one is the result of the other. Kids get vaccinated at almost every preventive-care visit (every three months) for the first two years, and most autism is diagnosed during that same period. When you think about how many millions of kids are getting shots, it makes sense that hundreds of them -- not a significant percentage, but a big number -- happen to develop ASD symptoms within 48 hours of a vaccination.

And again, it's not like this perceived correlation hasn't been extensively studied. The American Academy of Pediatrics (AAP) recently published a review paper (pdf) summarizing 29 studies that failed to find a link between the MMR shot and ASD and another 10 that failed to find a link between thimerosal (a preservative containing ethyl mercury) and ASD. "Failed to find" might sound like incompetence on the part of the researchers, so it's important to understand that it's usually impossible to prove a negative, so proving a negative is not the scientific standard. You will often hear from anti-vax activists that the MMR vaccine has never been proven not to cause autism, and that is strictly true, but neither has Tylenol. Neither have M&Ms. You can't prove something is safe, but on the other hand, harmful things are generally pretty easy to prove unsafe, especially when they're being given routinely to millions of people every year.

And you know what? Even if the evidence supported a link between the MMR vaccine and autism, I still might lean towards vaccinating. Autism can be heartbreaking, and I've already blogged about being afraid of it, but it doesn't kill 3 out of 1000 people who have it like measles does. It doesn't cause deafness, cataracts, and mental disability in 8 out of 10 infants of mothers who have it in early pregnancy like rubella does. Take a look at this pamphlet (pdf), from the AAP (based on Centers for Disease Control [CDC] publications) comparing the scientifically demonstrable risks of vaccines to the diseases they prevent. Choosing not to vaccinate isn't choosing to avoid risks: it's choosing to take different risks, and across the board, greater risks of mostly much more dire outcomes.

On one side of this debate is pretty much the entire medical, medical research, and public health community. On the other are a few physicians who are not scientists and a whole lot of passionate amateurs. The evidence on the pro-vaccine side is manifold, and it is backed up by established procedures of peer review and standards of scientific proof. The evidence on the anti-vaccine side is anecdotal and backed by nothing. The internet and cable news tend to present these two sides as more or less balanced: the internet because you can certainly find as many anti-vax sites as pro-, and the vast majority of the information, if presented with a bare minimum of layout competence, looks equally trustworthy on its face; cable news because it tends to bestow a level of expertise just by virtue of putting someone in front of the camera and slapping the title of "expert" on him whether he deserves it or not. Take a look at this clip from a Fox News segment on the H1N1 vaccine:

Dr. Holtorf, billed by the Fox anchor as an expert on infectious disease, claims no expertise on his own website in anything relating to vaccination or epidemiology. He is not a scientist or an expert on public health; he is a physician specializing in hormone replacement. He claims expertise in chronic infectious disease, like lupus, which is a far cry from expertise in epidemiology. In the clip, he says that thimerosal is "highly implicated" in causing ASD though the medical literature doesn't suggest any implication at all. He says it (presumably a single dose of the vaccine, though it's unclear) has 25,000 times the amount of mercury that would be considered toxic in food or water, which is simply not true: there are 25 micrograms of mercury in an H1N1 shot and 28 in a typical tuna sandwich. He says he's seen this vaccine "devastate" patients with chronic fatigue and fibromyalgia and implies that it would be similarly dangerous to pregnant women, but he doesn't specify the symptoms his patients suffered or how he determined causation or whether their reactions were life-threatening, as H1N1 certainly is to pregnant women. But if you saw this clip and were predisposed to distrust the federal government and the medical and scientific establishment, this jackass would have confirmed all your fears with the imprimatur of an established news source. And even had Fox followed this guest with an actual expert to refute the bogus claims, it would have looked like two experts who came to different conclusions, as if there's debatable evidence on both sides.

Anti-vax activists like to frame the debate in terms of personal choice: it's up to you to choose what's right for you child. And that's true. But I think you have a much higher standard of proof to meet when you choose not to vaccinate because you're not just choosing for yourself; you're choosing for your whole community. Some people, because of weakened or suppressed immune systems or certain allergies, cannot be immunized. And vaccines are not 100% effective. Those who can't be vaccinated and those who have been but happen not to be fully protected depend on herd immunity, the notion that, depending on a disease's virulence, once a certain percentage of the population has been inoculated, the lack of hosts acts as a kind of firebreak. If you don't vaccinate, you're putting kindling into the firebreak.

And this is why I have a lot of sympathy for the physicians who "pressure" their patients into getting vaccinated. Not only is it demonstrably in the patient's own best interest, it's in the best interest of all the doctor's other patients, too. Yes, it's unpleasant to have your convictions challenged, but do you really want a doctor who won't passionately advocate for what she thinks is best for your health and the health of your community, a doctor who won't challenge what she sees as your misconceptions or ignorance? Would you really prefer a doctor who doesn't read -- or worse, doesn't believe or can't understand -- the results of scientifically rigorous medical research? And if you're so sure that vaccines are the wrong choice that you're willing to bet your kid's health and the health of everybody in your community on it, you should be able to go toe-to-toe with the biggest bully in town to defend your conviction. Right?

American Academy of Pediatrics Immunization page

Centers for Disease Control vaccines page

Autism and Vaccination (2007)
Vaccines and Autism: a Deadly Manufactroversy (2009)
at Skeptic

As Flu Vaccine Arrives for the Season, Some Questions and Answers
An H1N1 primer in The New York Times

Andrew Wakefield and MMR - The Investigation

at the site of Brian Deer, the reporter who covered the story

A Pox on You: My son has cancer. He can't go into daycare because of unvaccinated children.
In Slate.