Approximately one-third of humanity, especially in developing countries, is infected with parasitic roundworms or flatworms, collectively known as helminth parasites. These infections cause severe diseases, delayed physical development and mortality. A person in helminth endemic areas may be infected with these parasites all his life. These parasitic infections coincide with many other infectious diseases, such as malaria, tuberculosis and HIV. Treatment of these parasitic infections is relatively easy. In some cases a single dose of anti-parasitic treatment suffices. This paper briefly reviews the effects that helminthic infections have on other infectious diseases; on chronic non-transmittable diseases and discusses the potential benefits that de-worming may have on the overall morbidity and mortality associated with these diseases in developing countries, as well as on the effect de-worming may have on vaccination efficacy. We conclude that successful mass de-worming is essential for the reduction of the morbidity associated with these infections and may be a feasible and affordable means to combat other infectious diseases, such as HIV, malaria and tuberculosis. Furthermore, without it, HIV, malaria and TB vaccines may fail to confer protection in helminth endemic areas.