Evidence, opportunity, ethics, and the allure of zero leprosy

After a decade in which the long-term downward trend in the number of people diagnosed with leprosy (also known as Hansen’s disease) has stalled, there is new momentum toward a vision of zero leprosy. This has been facilitated by scientific advances, particularly related to post-exposure prophylaxis (PEP) for leprosy, and the coming together of the leprosy community in a new Global Partnership for Zero Leprosy. The World Health Organization is in the process of drawing up Guidelines for the use of PEP with single-dose rifampicin (SDR) for national leprosy programmes, although some investigators have expressed reservations regarding the robustness of evidence for its effectiveness; the potential for drug resistance; and ethical issues related to implementation of PEP, including informed consent and disclosure of leprosy diagnosis. Many of the same concerns have been raised and addressed in other neglected tropical disease (NTD) control and elimination programmes. I review features of these NTD control programmes, highlight benefits of the increasingly close relationship between the leprosy community and the larger NTD movement, and examine concerns regarding scaling up of PEP in light of the NTD experience. The fundamental question, “How much evidence is required to scale up a promising intervention?” is a perennial one in public health. In addition to drawing upon lessons from other NTD control and elimination programmes, I examine this question with reference to ethical principles in public health and suggest that the answer is not found in a yes/no dichotomy, but rather, in moving forward to scale up PEP within national leprosy programmes while incorporating 1) operational research to strengthen the evidence base; 2) robust monitoring for drug resistance; and 3) procedural safeguards as well as strong stakeholder engagement to protect human dignity and ensure adherence to the highest ethical standards.