California ends personal belief and religious exemptions for childhood vaccinations

California has recently ended most exemptions from childhood vaccinations. Only exemptions for medical conditions remain, and such exemptions must be certified by a physician. The requirement applies to children attending elementary or secondary school, as well as day-care centers; home schooled children are not included. A recent editorial in the New England Journal of Medicine reviews the politics behind passage of the new law.

Clearly the recent outbreak of measles in the state played a large role in convincing the legislature to pass the law. That, plus the progressive fall in the percentage of children vaccinated. Epidemiological research has shown that when the percentage of the population that is vaccinated falls below a certain number, what is termed herd immunity no longer functions. That concept is that, if the great majority of the population is immune to a disease, the few who are not are protected by the overall rarity of the infection. The particular threshold for herd immunity varies with the disease, but it is usually in the neighborhood of 80-95%. The more infectious the disease, the higher the percentage of immune people needs to be to prevent spread. If sufficient herd immunity can be maintained for long enough, the disease can actually be eradicated. Thus far only smallpox and rinderpest (a disease of cattle) have been eliminated in this way. Perhaps the purest example of the importance of herd immunity is whooping cough, or pertussis. The people most prone to contract severe, even lethal infection are small infants. Yet they cannot begin to get the vaccine (it takes several doses) until they are several months old because it doesn’t work before that age. They are entirely dependent upon not encountering older persons who have the disease.

In my view, vaccine requirements are lawful applications of the state’s interest in public health. Adults have a right to do whatever they like to their bodies (although not their children’s) as long as their actions don’t affect others. In the case of vaccines, not participating in maintenance of herd immunity has significant and potentially serious effects on the health of others.

More here.


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