There is something I mentioned briefly in my previous vaccine post that I think deserves a little more thought. That is, the diagnosis of vaccine-preventable diseases (VPDs) before and after vaccines are introduced. It’s difficult to say exactly how many cases of VPDs go undiagnosed now, since they are undiagnosed! Most of what is out there is anecdotal, rather than scientific, but it is easy to see how this could be the case and how it could influence statistics the CDC uses when talking about the number of cases.
For example, take this statement from the AAP:
KEEP A CLEAR AND UP-TO-DATE RECORD OF IMMUNIZATIONS. This can help doctors do a better job of diagnosing a problem in an emergency. For example, if your child has a bad infection, and the doctor knows your child has been vaccinated against Hepatitis, the doctor can rule that out. This can save time.
This is basically stating that if your child has been vaccinated for a particular disease, that disease can be ruled out right away to make everyone’s life easier. The problem is that this assumes that vaccinations are 100% effective, which even the most glowing vaccine reports can’t say. Inside Vaccines has a list of VPDs with the information from the vaccine inserts stating their efficacy. A quick look at the Hepatitis information (taken directly from the manufacturer’s statements) shows that the Hep B vaccine is only 50% effective after 1 dose, and 70-90% after multiple doses.
A look at the DTaP information shows it as being 59-89% effective. But if you bring your child into a doctor with a persistent cough, wheezing, etc. and he or she has been vaccinated, your doctor is much more likely to diagnose bronchitis or atypical asthma than whooping cough, especially if the doctor hasn’t heard the cough (and therefore the characteristic whoop). And of course, if diseases aren’t getting diagnosed properly, it makes the vaccines look more effective than they are, so the 59-89% efficacy rate might actually be quite high. A New Zealand study published in the Journal of Theoretical Biology found that the efficacy rate might be as low as 33%.
Another example is chicken pox (varicella). I know of more than one parent who brought their vaccinated child to the doctor’s with a suspicious rash and known exposure to chicken pox, only to be told it couldn’t be chicken pox because they’ve been vaccinated. The official diagnosis in most of these cases ends up being: “a varicella-like viral infection”, and the treatment suggested is the same as would be suggested for chicken pox, but the vaccine is still considered to have worked. This is anecdotal of course. The official documentation states the vaccine is 83% effective after one dose and 98% effective after two doses, but both the Journal of Infectious Diseases and The New England Journal of Medicine have published studies showing an effectiveness closer to 44%.
Besides a lower rate of diagnosis, another way that cases can be shown to be dropping is by changing the diagnostic criteria, as happened in the case of polio. If you’re interested, there are a lot of quotes on that website about how the definition for polio was changed and the effects that had on the diagnosis of the disease and how it made the vaccine look effective. Here is one explanation.
Dr. Bernard Greenberg, a biostatistics expert, was chairman of the Committee on Evaluation and Standards of the American Public Health Association during the 1950s. He testified at a panel discussion that was used as evidence for the congressional hearings on polio vaccine in 1962. During these hearings he elaborated on the problems associated with polio statistics and disputed claims for the vaccine’s effectiveness. He attributed the dramatic decline in polio cases to a change in reporting practices by physicians. Less cases were identified as polio after the vaccination for very specific reasons.
Prior to 1954 any physician who reported paralytic poliomyelitis was doing his patient a service by way of subsidizing the cost of hospitalization and was being community-minded in reporting a communicable disease. The criterion of diagnosis at that time in most health departments followed the World Health Organization definition: “Spinal paralytic poliomyelitis: signs and symptoms of nonparalytic poliomyelitis with the addition of partial or complete paralysis of one or more muscle groups, detected on two examinations at least 24 hours apart.” Note that “two examinations at least 24 hours apart” was all that was required. Laboratory confirmation and presence of residual paralysis was not required.
In 1955 the criteria were changed to conform more closely to the definition used in the 1954 field trials: residual paralysis was determined 10 to 20 days after onset of illness and again 50 to 70 days after onset…. This change in definition meant that in 1955 we started reporting a new disease, namely, paralytic poliomyelitis with a longer-lasting paralysis. Furthermore, diagnostic procedures have continued to be refined. Coxsackie virus infections and aseptic meningitis have been distinguished from paralytic poliomyelitis. Prior to 1954 large numbers of these cases undoubtedly were mislabeled as paralytic poliomyelitis. Thus, simply by changes in diagnostic criteria, the number of paralytic cases was predetermined to decrease in 1955-1957, whether or not any vaccine was used.
One other thing to keep in mind when looking at disease statistics is that because of this misdiagnosis, many diseases look worse than they really are. For example, a disease might only be diagnosed properly because a patient is presenting with the worst symptoms, or needs to be hospitalized, while children who are mostly asymptomatic or only minorly ill may not be brought to a doctor at all or are misdiagnosed. This would of course skew the statistics to make it look like that disease hospitalizes a lot more children than the reality. For a really good explanation of this along with lots of citations, have a look at the measles page on Inside Vaccines.
I am still planning on writing my thoughts on the various diseases we vaccinate against. In the meantime, I highly recommend that anyone interested in vaccinations at all include the Inside Vaccines website in their research. There is a lot of good information and studies linked, along with citations and references to lead you to more material to read. They have an excellent article entitled “Where to Start?” for parents who are just beginning to research the issue, which provides places to search for information on both sides of the issue.