We discuss ethical aspects of risk-taking with special focus on principlism and mid-level moral principles. A new distinction between the strength of an obligation and the degree to which it is valid is proposed. We then use this distinction for arguing that, in cases where mid-level moral principles come into conflict, the moral status of the act under consideration may be indeterminate, in a sense rendered precise in the paper. We apply this thought to issues related to pandemic influenza vaccines. The main conclusion of the paper is that on a principlist approach some acts may be neither right nor wrong (or neither permissible nor impermissible), and we claim that this has important implications for how we ought to make decisions under risk.