With more and more families opting out of vaccinating their kids, one of the most sacred of public health goals, the concept of herd immunity, is being threatened.
A recent piece in Scientific American featured tantalizing graphics — on view above — illustrating this scary trend. According to this analysis, the vaccination rates in some states — Oregon, West Virginia and Colorado, for instance, are shockingly low. So low, in fact, that they’ve dropped below the “herd immunity” levels (or what is thought to be the safe threshold) for MMR (measles, mumps and rubella) and DTP (diphtheria, tetanus and pertussis).
So what’s the deal with herd immunity? According to the CDC, a population has reached herd immunity when a sufficient proportion is immune to a particular infectious disease. Immune population members get that protection either by being vaccinated or by having a prior infection.
The epidemiological concept is based on this logic: Continue reading