When it comes to public health, how far should governments compel people to do what is good for others?

Vaccines are also very safe. They are dispensed by the million, so side-effects would be easy to see if they existed. But no medicine can be entirely without risk. In a large population, a few people will have a rare, strong reaction to even the safest substance. Moreover, as a disease becomes vanishingly rare—as diseases like measles and whooping cough have in the West—it follows that adverse reactions to the vaccine, however rare they in turn may be, will become more common than the disease itself.