We propose to analyze the specificity of ethical problems in public health issues and to elucidate the applicability of principlism as a problem-solving strategy in this realm. Although well-established in clinical ethics, principlism is not an adequate model to be used in public health, since it is basically intended to serve as a moral guide in the physician-patient encounter. We discuss the possible adequacy of principles like "solidarity", "ontic responsibility" (as proposed by Jonas), and "caring or diaconal responsibility" as presented by Lévinas. Solidarity appears to be insufficiently specified, whereas the other two perspectives may be adapted to public health issues by bringing together Jonas' ontological and Lévinas' transcendental concerns to form a principle of protection that might better serve the purposes of such an ethics. This principle would help to identify more clearly the goals and agents involved in the implementation of public policies that are expected to be both morally correct and pragmatically effective.