I wrote about the rationality or irrationality of the anti-vaccination movement last March, and concluded that the decision not to have one's children vaccinated may be rational from a purely selfish and narrow point, but that it's deeply irrational from a wider societal point of view:
But the decision not to have one's children vaccinated can also be a rational one, though only on a narrowly selfish basis, at least as long as herd-immunity prevails:
If almost all the other parents in the area have vaccinated their own children and if the custom of vaccination is old enough so that almost all adults in the community have immunity, too, then the benefits from vaccinating your own children become negligible. Your child won't get infected!
But any kind of vaccination may have harmful, though rare side-effects. The private (based only on one's immediate family) comparison of benefits from the vaccination to its costs, both financial and possible health risks, would strongly suggest that for one particular family the choice not to vaccinate can be rational*.
Given that you are smart and erudite, my dear readers, you have already spotted the logical flaw in the above calculations: If not getting the shots is narrowly rational for the one family in the above example, then it is narrowly rational for all the other families, too!**
But once a sufficient number of families chooses not to vaccinate, whoops! The herd immunity is gone, the infectious diseases return to the communities, and there will be deaths and very high health care costs and unnecessary pain and suffering***.
Economic theory looks at dilemmas like this as signs (1) that a particular market (here the market for vaccinations) is not producing the socially optimal level of disease prevention and that government intervention in that market may improve the outcomes. The German government, for instance, is planning to make childhood measles vaccinations mandatory.
The recent mass murders in Gilroy, El Paso and Dayton, all carried out with assault weapons, made me ask if there are similarities between those who oppose vaccinations and those who oppose gun control, and if those similarities suggest that some kind of regulation of the relevant markets (vaccinations and guns) might be beneficial.
I believe I found one similarity. The choice to acquire or to keep guns, and to fight gun control attempts for that reason, is made on the basis of a similar narrow private calculus. That calculus does not assign any weight on the great social harm easy access to guns causes to others (2). This might (2) be a reason for controlling the gun market and the excessive number of guns in the US.
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(1) This is because the private comparison of benefits and costs excludes the benefits accruing to other individuals in the community, even though those are the benefits which ultimately end up protecting any unvaccinated children via herd immunity. Thus, the private calculus results in too few children getting the vaccinations.
(2) That's the similarity between anti-vaxxers and anti-gun-control folks. But then the two cases diverge, because anti-gun-control people fear all those guns already out there and see owning guns themselves as a necessary defense.
In other words, they don't just exclude the harm to others in their private calculus concerning gun ownership and anti-gun-control stances, but include the general easy access to guns as one reason why they, too, need to be armed to the teeth.