Background: Many behaviors affect not only the self but also others. The utility of a vaccination to each individual depends on population immunity, the cumulative result of individual vaccination decisions. However, little is known about how the benefit to others influences vaccination decisions.
Methods: In a series of 3 experiments (N = 292, 316, and 299) using hypothetical scenarios and college student respondents, we tested whether the vaccination decisions of individuals were sensitive to the level of immunity in the population when it had implications for either altruistic or free-riding vaccination behavior.
Results: Our findings indicate that decisions of individuals were sensitive to opportunities both to free ride by refusing vaccination and to vaccinate altruistically. Although individuals were most willing to get vaccinated when they were at risk themselves, they were also sensitive to the amount of good they could do for others. This altruistic sensitivity was strongest when individuals were not vulnerable to the disease themselves.
Conclusions: The most effective vaccination strategies, from a public health perspective, often entail vaccinating the disease transmitters rather than those who are most vulnerable. Consequently, those who bear the burden of vaccination and those who benefit are not the same individuals. Thus, effective vaccination campaigns require that disease transmitters vaccinate even when it is not in their self-interest to do so. Our results suggest that it may be possible to encourage vaccination by appealing to altruistic motives.