Posted by: Chris Maloney | December 2, 2011

Increased Vaccine Requirements = Increased Exemptions. The Myth of Herd Immunity.

Despite Maine’s 97% vaccination levels, public health officials voiced concerns over increasing exemptions in today’s Kennebec Journal article.  There was no data on the varicella vaccine, which is now required and is likely to have caused any increase in exemptions as a few parents decided it wasn’t really something they wanted to have their children take.

If HPV vaccination becomes mandatory, we’ll likely see another increase in exemptions.  The overwhelming, vast majority of Maine’s parents will dutifully get their children that one as well, but a few will wonder about making everything mandatory, especially if boys are included in the mandate.

In fact, as more and more vaccines become mandatory, an ever-increasing number of parents will start opting out of at least some of the vaccinations.  It’s just that they will make absolutely no difference in the health of the state as a whole.

The idea of total vaccination is that we can maintain herd immunity.  Health officials won’t say what the number necessary is, but let us be clear that with full vaccination, the vaccines are 80% effective at preventing the disease.  This is a very generous estimate, as the CDC’s own estimates of disease prevention are between 60-80%.  The ability of a vaccine to generate a sufficient response varies widely from population to population.

So at 100% vaccination compliance, we would still have a very real chance of an epidemic of any of those diseases still going through the state among individuals who have been vaccinated but who did not generate a sufficient immune response.  In recent years the outbreak in Maine of Mumps was among vaccinated children.

So what is the vaccine coverage goal that would provide the maximum coverage possible?  According to the U.K. health goals, it’s 95%According to public health officials, the number is more in the range of 85%.   At that level, it’s thought that an epidemic of a disease is impossible and the disease will cease to exist within a population.

We’ve achieve herd immunity here in the U.S. for years.  But it doesn’t stop periodic outbreaks.  By increasing the bar to an impossible 100%, public health officials are deflecting the reality that the vaccines themselves are far more of a problem than any of the few individuals opting out.

Even if the vaccines were improved to 100% efficiency (again, an impossible target), there would still be periodic outbreaks of disease.  In a recent study of Hib vaccination, the type B that is vaccinated for is much less common.  But non-type B (wild strain) Hib is still an issue.  While most diseases mutate much less rapidly than the influenza virus, they do mutate swiftly enough to continue to be a problem for decades to come.

None of this means that people should not get vaccinated.  Vaccination can be life saving, especially in populations where malnourishment is common.  But we should not try to explain absolutely predictable periodic outbreaks of disease as being due entirely to parental resistance.  The numbers just don’t add up.


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