One of the mercies of immunity produced by vaccination is that a small number of people can forgo vaccination without putting themselves or others at greatly increased risk. But the exact number of people this might be—the threshold at which herd immunity is lost and the risk of disease rises dramatically for both the vaccinated and the unvaccinated—varies depending on the disease and the vaccine and the population in question. We know the threshold, in many cases, only after we’ve exceeded it. And so this puts the conscientious objector in the precarious position of potentially contributing
...more
