Clarifying my views on chicken pox vaccination

First of all, let me say that the discussion with Dr. Novella and Orac has been partly enjoyable, as in sharpening my debate skill, and partly like a school yard brawl, which I will invariably lose because I am not interested in that kind of a zero-sum game. It is all well and good to say that your tone is your tone, but it is an altogether different matter when personal attacks are involved. I know, I started it. But did I really? Well, no matter, that is quite unimportant.

Here are a couple of interesting bits. First of all, go to this blog, where Eddy Jenner, a clinician in Australia, blogs about his encounters with EBM at the bedside -- he provides a fascinating, well-reasoned and well-read perspective. His most recent post is illuminating particularly in the context of the current discussion. It reminded me that I am much more interested in general in improving everyone's understanding of how we do clinical research than debunking alternative approaches. 

Next, I want to articulate why it is I think that chicken pox and HPV vaccines strike me as being less straight-forward than, say smallpox, polio or pertussis. There are 3 things to remember about medicine as a science:

1. With every intervention's benefit there is also a risk of an adverse event.

2. What we think we know today will be different in a decade.

3. It is the obligation of medicine first to do no harm.

None of the 3 statements is particularly controversial or new, and I think everyone can agree on them. So, what? 

Here is the so what. Since what we know today is necessarily incomplete, it is quite probable that there are many risks to our treatments, which today we just do not have the data to understand, but will be known in the future. Alas, we do not have a crystal ball to see what is coming down the pike, so, being circumspect about what we are so sure about today should be the norm. For example, when the risk of serious complications from a disease is extremely high (think smallpox, polio, diarrheal diseases in Africa, etc.), then, if the treatment (vaccine) diminishes this risk substantially (how about no more smallpox?), and there is no immediate reason to think that the risk of that treatment is overwhelming, then the risk-benefit equation is hard to tilt away from the benefit. However, when the risks of the complications or death from a particular disease are not that high (relatively speaking, of course), then one really has to examine the risks of the intervention with a much finer lens. And indeed, here is a study on chicken pox vaccination and deaths that showed that from pre-vaccination period to post-vaccination period deaths declined on average from 145 to 66 per year. So, that's pretty good, if there were absolutely no deaths associated with the vaccine itself. But invariably, there are, and this is less a function of the vaccine safety than it is of the human substrate that is being injected. In fact if you check CDC Wonder's VAERS, you will see that on average there are about 14 annual deaths that may be related to varicella vaccination. Now you may say that the balance of this intervention is in the direction of the benefit, and you will be correct. But the magnitude of this benefit makes me a bit cautious. If we were talking in purely scientific terms, I would worry about the possibility of type I error, where the difference is really there by random chance. But we also know that we are not all rationality and science, and there is a lot of emotion involved in this debate. So, it is easy to see how these numbers lead to a variety of interpretations and opinions. And add to this the idea that it is not inconceivable that some other safety signal may come along in the future, and it becomes patently obvious why the issue is difficult to reduce to either ethics or idiocy when one is really committed to science and its principal nostrum of "first do no harm".      

Are vaccines safe?

The H1N1 pandemic is bringing into focus not only the world's vulnerabilities vis a vis the spread of an infectious disease, but also our complete lack of a framework in which to make rational choices about prevention. The cornerstone of preventive efforts for any significant infectious disease is vaccination of a large swath of the population. The rapid development and approval of the H1N1 vaccines is both a blessing and a curse, given the sophomoric level of discussion about its risks and benefits. By coincidence this discussion has extended into the world of HPV vaccination, with a high profile death of a 14-year-old girl in the UK one hour following inoculation with Cervarix, the GSK's HPV shot. Though upon a post-mortem examination it is clear that the girl's death was a result of a malignant tumor invading her chest and not of Cervarix, the level of panic and skepticism about the vaccine is illustrative of the polarization of public opinion on the very philosophy of vaccination itself.

Why do we even have vaccines? To put it simply, vaccines are there to prevent highly infectious agents from causing mass morbidity and mortality. In the US, states mandate that children undergo certain vaccinations as a prerequisite for attending school. In fact, save for a handful of states where parents can express intellectual objections to some vaccines, in most states, including my own, the only acceptable reason for not vaccinating a child is a religious objection. And this is an all-or-nothing situation, where you are forced to either get the entire panel of shots or nothing. These laws, written decades ago, have taken individual decision making out of the public's hands. They leave no room for engaging in an educated risk-benefit analysis for the individual situation.

Rabid vaccine advocates would argue that there is never a need to make individual decisions in diseases where a vaccine is available. Well, let's take the chicken pox vaccine. Here is a childhood disease that is indeed highly contagious, but only causes a self-limited nuisance illness with a very low risk of complications in the pediatric age group without underlying conditions. In the US the disease was associated with ~10,000 hospitalizations and on average 105 deaths annually in the pre-vaccine era. So, is this really a big deal? Well, yes, from the perspective of those families suffering the 105 fatalities. But what about the societal concern? This is well summarized in the recommendation rationale from the American Academy of Family Physicians: 

Because chickenpox is so contagious, a child with chickenpox shouldn't go to school or day care until all the sores have dried or crusted. Many parents miss work during the time their child has chickenpox. Because of the lost time from work, chickenpox can be a significant cost to parents of children who get the illness. [emphasis mine]

So, there is clearly an economic risk that drives at least some of the rationale for requiring this vaccine. This then begs the question: should economic considerations ever drive a government mandate for vaccination? Note, economic considerations do not fall into what I put forth as the rationale to vaccinate: to prevent spread of highly contagious disease that causes wide-spread morbidity and mortality. Now it becomes about the money. So, does it not stand to reason that I as a parent should be able to take into account my personal situation with respect my aversion to missing work days to stay home with a sick child and make this vaccination decision myself?

Unfortunately, I do not believe that most citizens are equipped with the skills to make these informed choices. Since we have broadly accepted the government's judgment as to who should get vaccinated with what, we have not been taught systematically to make these choices rationally. And here we are, in 2009, faced with the swine flu and HPV choices: to vaccinate or not?

Ignorance is fertile ground for breeding fear. Hysterical rhetoric on both sides, anti-vaxers and vaccine apologists, is promoting a climate of confusion. When a radio program polls its listeners on whether or not they believe the H1N1 vaccine is safe, what are they looking to accomplish? As scientists we know that the concept of safety does not exist in a vacuum. How do you define safe? Safe for whom? Is there a gradient of safety? And what do the loud and often non-sensical caller responses accomplish but to create more noise at the margins?

A more constructive approach in the short-term would be to present the populace with facts -- both risks and benefits of both the diseases and the vaccines against them. (And yes, the reality is that diseases AND vaccines will have risk-benefit profiles that differ for different people.) But this short-term tactic will not solve our general inability to make rational choices when faced with complex ideas. This shortcoming needs to be addressed in our educational institutions. This knowledge will serve us in far more ways than just deciding whether or not to vaccinate our kids against chicken pox.