Trick or Treat: The Role of Vaccines in Integrated Schistosomiasis Control

Recent systematic reviews [1,2] indicate that the geographic extent and burden of schistosomiasis exceeds official estimates. The risk for infection is particularly pronounced in sub-Saharan Africa, but also exists in many parts of South America, the Middle East, and Southeast Asia. Collectively, close to 800 million individuals are at risk of schistosomiasis, and over 200 million people are infected [2]. The disease can be controlled with vigorous political and financial commitment, but local elimination has proved difficult in reality. The cost of treatment with the only available drug—praziquantel—has become affordable, and hence preventive chemotherapy is being advocated on a large scale [3]. However, a strongly biased approach, devoid of any emphasis on prevention, access to clean water and improved sanitation, and snail control, demands indefinite drug distribution [4,5]. Although praziquantel-based morbidity control has proved successful, it has an intrinsic weakness, which is intimately related to its inadequate impact on transmission even when chemotherapy is provided according to schedules carefully adjusted to the local setting [6]. Genuine change of the disease spectrum in endemic settings demands lasting results which can only be obtained by long-term protection involving vaccination. An entirely vaccine-based approach to schistosomiasis control is unrealistic, but we advocate that acceptable protection could be achieved by chemotherapy followed by vaccination aimed at reducing, or markedly delaying, the development of pathology [7]. Thus, the issue is not vaccines versus chemotherapy, but how to graft a vaccine approach onto current schistosomiasis control programs. This, we believe, would fit well with the scope of the ‘‘Schistosomiasis Research Agenda’’, particularly in the areas of ‘‘Basic Science’’, ‘‘Tools and Interventions’’, and ‘‘Disease Burden’’ advanced by Colley and Secor in their recent Policy Platform article in PLoS Neglected Tropical Diseases [8] and the linked Expert Commentary [9].