11:00 Dose of Vaccinology: Why Does my Kid Need a Diphtheria Shot When No One Gets That Anymore?

The answer to this question is elegantly simple: "no one gets diphtheria anymore" because most of the people in the general public are vaccinated.  The organism that causes this disease, Corynebacterium diphtheriae, is alive and well on Planet Earth.  The protein it makes that causes the disease diphtheria ("diphtheria toxin") is kicking around, ready and waiting.  The reason you do not see this disease is because most of the people you encounter have antibodies, generated during vaccination, that soak up diphtheria toxin before it can cause illness.

There is excellent real-word evidence for this in two forms:

1.) The bacteria and the toxin are readily detectable in animals and even in healthy (vaccinated) humans (if this seems counterintuitive, tune in at 4:00 for an explanation).

2.) Destabilization of governments often leads to declines in vaccination rates, usually due to the closures of clinics and hospitals, shortages of vaccine doses, or the loss of programs that paid for them.  There are numerous examples of this (the polio outbreak in Syria last summer, for one, and the TWO within the US this past year-more at 12:00), but an extremely well-characterized example with diphtheria came after the fall of the Soviet Union in the early 1990s.  Again, this is certainly not unique to diphtheria.

The things about microbes is that they're invisible.  Just because you don't see them doesn't mean they're not there.