Vaccines and evidence

Salon.com has recently reviewed a new book by pediatrician Dr. Paul Offit on the anti-MMR (and anti-thimerisol) vaccine movement. Back in February this year, a friend of mine wrote to me that she was “on the fence” about vaccinating her infant. As she put it, “Whom are we to believe?…I’d be interested in anything compelling on either side so I could just move on either way.  My confidence in institutions is at an all time low.”

My response to her (revised for this blog) reviewed some evidence, much of which also appears in the Salon article:

Among doctors, there is really no question. The one published study that claimed a relationship between MMR vaccine and autism has been renounced by 10 of the 13 authors and retracted by the journal (for some relevant links see http://blog.openmedicine.ca/node/50).

With respect to thimerisol, it’s out of all childhood vaccines in the US right now, except for some flu shots. See http://www.cdc.gov/nip/vacsafe/concerns/thimerosal/faqs-thimerosal.htm. The one study in this area that claimed a link was also authored by a pair of docs who make their money as expert witnesses and was seriously flawed.

The purported link is, at base, no more than a scam to make profits off of people who have the misfortune to already be dealing with how to raise their autistic child and are accustomed to (rightly) standing up to recognized authority in other matters related to their children (e.g. education).

Since 2001, thimersol has been removed from vaccines, and autism rates have increased. And now measles is making a comeback.

What is known is that vaccines have made many childhood diseases
nearly extinct in the US, and saved a ton of lives and health.
E.g. http://www.cdc.gov/mmwR/preview/mmwrhtml/00056803.htm

Readers of this blog will know that I think scientific evidence is a good thing in medical decision making. But looking over my response, I wonder if I really addressed her key uncertainty: “My confidence in institutions is at an all time low”

Unfortunately, I think there are many people who are concerned about the trustworthiness of public health research and recommendations (and perhaps too few people who are concerned about the trustworthiness of pharmaceutical company research, but that’s a different story). Some of this concern is undoubtedly justified, as I wrote, because people who are raising autistic kids or living with other disabilities do have to be critical of the institutions around them, and often must make their voices heard loudly in order to secure equitable and beneficial treatment of their children and themselves in non-medical arenas. It is hard to avoid skepticism about medical science if you’re African American and familiar with the Tuskegee studies. IUD use is very low in the U.S., despite its safety and effectiveness, in part because of memories of problems with the Dalkon Shield. And sometimes things that look good, like thalidomide, do turn out to be bad.

As we wrote in the book, uncertainty is a fundamental feature of medicine; on the other hand, decisions have to be made. For vaccination, the default option (the one proposed by nearly all pediatricians) is to vaccinate, and that’s a good thing, but once a treatment has entered the public consciousness as uncertain, people will rightly want to make a more considered decision. A key question for physicians and patients alike is how much evidence, and what kind, should we expect in order to make these decisions, and how can we be sure we’re hearing reliable evidence and not biased evidence? This is a particular problem because, much of the time, good science speaks softly; bias shouts.

There are some time-honored heuristics that serve well here. Prefer evidence that you seek yourself to evidence that someone else thrusts at you. Prefer evidence that can clearly be replicated, that has received open scrutiny from other scientists, and especially findings that have been replicated repeatedly. Ask “cui bono?” Understand statistical reasoning. Recognize that in a nation of 300 million people, a one-in-a-million chance will happen about 300 times. Compare medical risks to other risks that you’re willing to undertake in daily life for similar benefit. Remember to consider the risks incurred by choosing not to choose.

Comments

  1. The following news item describes how the MMR scare unfolded in the UK. The author, a journalist who is a practising doctor, also notes that vaccination scares often differ between countries.

    http://www.badscience.net/2008/08/the-medias-mmr-hoax/

    A mental models analysis of parents’ understanding of vaccination issues has just been published by Julie Downs, Wandi Bruine de Bruin and Baruch Fischhoff: “Parents’ vaccination comprehension and decisions”, in Vaccine, 26, 1595-1607.

  2. The Downs, Bruine de Bruin, and Fischhoff study is a really neat piece of work, David. Thanks for calling it to my attention!

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