As medical products given to healthy people (mostly children) at least partly for the benefit of others, vaccines raise challenging ethical questions. A vaccine provides a dual benefit: a direct benefit to the person receiving it, and an indirect benefit to other members of the community through the creation of herd immunity. As with any medical intervention, immunization also carries risks of adverse events. The collective implications of immunization have led governments to enact policies designed to achieve high rates of coverage among their populations. This article provides a historical overview of vaccine use and considers ethical questions related to compulsory vaccination, coercion, vaccine rationing, and compensation for vaccine-related adverse events.