Validity of studies on the association between soil-transmitted helminths and the incidence of malaria: Should it impact health policies?

Introduction: The global distribution of malaria and soil-transmitted helminths is widely overlapped. Some studies suggest a possible association between helminth infection and incidence of malaria. Objectives: To identify the available epidemiologic evidence and to assess the validity of these studies. Methods: A systematic review was carried out in specialized databases. The studies identified were critically analyzed and ranked according to the U.S. Preventive Services Task Force's classification. The major methodological limitations of each study were identified. Results: Six studies on the topic were found. Only two studies had a high evidence level (level I), three had level II-2, and one had level III-3. There are important methodological limitations for clarifying the association between soil-transmitted helminths and the incidence of malaria. Conclusion: It is too early to discuss the potential public health implications of these findings, given the lack of studies and limited validity of the evidence available. Further studies with new methodological considerations could improve the knowledge on the association. However, it is more important to carry out actions on structural determinants to control and prevent the occurrence of both diseases.