As long as there have been vaccinations, there has been an antivaccine movement, and as long as there has been an antivaccine movement, there have been parents who refuse to vaccinate. In a past that encompasses the childhood of my parents, polio was paralyzing and killing children in large numbers in yearly epidemics, the fear of which led to the closure of public pools every summer. In such an environment, the new polio vaccine introduced by Jonas Salk in the mid-1950s wasn’t a hard sell. In fact, satisfying the initial demand for it was the problem, not parents refusing to vaccinate their…