Game Theory and Vaccination
A couple months ago, the state of California passed a law that makes vaccination obligatory in public and private schools. A wise decision, given that a growing number of parents, scared of possible side effects, decide not to vaccinate their children. Although vaccination might not be 100% effective, it’s still the best way of preventing a person from a disease. If the majority of people are vaccinated, and hence less likely to catch the disease, an outbreak is less likely to happen, which benefits everyone (herd immunity). The problem is that, when a community benefits from herd immunity, incentive to vaccinate decreases, which causes parents to free ride (benefit from something without contributing to it) the high immunization rate without vaccinating their children. If enough parents free ride, all of them end up losing the benefit: the population will not be safe from an outbreak.
In my point of view, the game is as follows: let the players be an anti-vaccines parent (who thinks they do more harm than good) and a school. Their strategies are the same, to vaccinate (V) and not to vaccinate (N). If both vaccinate, the payoff is low for the parent (who is against it), but high for the school, because it will be safe from the disease. If the parent vaccinates but the school doesn’t, there’s no payoff for either, because not only was the child vaccinated, it will probably not work, given the school is not safe. If the parent doesn’t vaccinate but the school does, both get a high payoff, because the school will still be safe, and as a result so will the child (without having to be vaccinated). If neither vaccinate, the school still has no payoff, because it isn’t safe, but the parent gets a low payoff because it didn’t have do vaccinate the child.
Because there is a dominant strategy for both, we can predict that the parent won’t vaccinate and the school will. The problem is that if a high number of parents join the “anti-vaxxers” and start thinking of vaccines as prejudicial, the school won’t be safe even vaccinating. That’s where the law makes sense. By taking the decision from the parents, it resolves the social dilemma and assures the most beneficial scenario for all children.