Essays on the collective action dilemma of vaccination

Sammanfattning: Vaccines famously possess positive externalities that make them susceptible to the collective action dilemma: when I get vaccinated, I protect not only myself, but also those who I might otherwise have infected. Thus, some people will have an incentive to free ride on the immunity of others. In a population of rational agents, the critical level of vaccination uptake required for herd immunity will therefore be difficult to attain in the long run, which poses difficulties for disease eradication.In this doctoral dissertation, I explore different implications of the collective action dilemma of vaccination, and different ways of ameliorating it. First: given that coercion or force could solve the dilemma, and democracies may be less likely to engage in policies that violate the physical integrity of citizens, democracies may also be at a disadvantage compared to non-democracies when securing herd immunity. In essay I, I show that this is, empirically, indeed the case. Barring the use of extensive coercion therefore necessitates other solutions.In essay II, I highlight the exception to individual rationality found in other-regarding motivations such as altruism. Our moral psychology has likely evolved to take other's welfare into account, but the extent of our prosocial motivations vary: a wider form of altruism that encompasses not just family or friends, but strangers, is likely to give way to a more narrow form when humans pair-bond and have children. This dynamic is shown to apply to the sentiments underlying vaccination behavior as well: appeals to the welfare of society of getting vaccinated have positive effects on vaccination propensity, but this effect disappears in people with families and children. On this demographic, appeals to the welfare of close loved ones instead appears to have large effects.In essay III, I investigate whether the prosocial motivations underlying vaccination behavior are liable to be affected by motivation crowding - that is, whether they are crowded out when introducing economic incentives to get vaccinated. I find that on average, economic incentives do not have adverse effects, but for a small minority of highly prosocially motivated people, they might.