Effect of Helminth Infections on the Immunogenicity and Efficacy of Vaccines: A Classical Review

Abstract

Vaccines are responsible for the reduced cases of mortality caused by infections worldwide. However a number of studies have shown that helminth infections have strong immune modulatory effects. Due to this, they have been considered as one of the contributing causes of lowered immune responses induced by vaccines observed in developing areas, where these infections are endemic. This is often due to the host’s inability to mount an effective protective immune response once receiving the vaccine. Nevertheless, it has been shown that elimination of the helminth infections, with the use of antihelminthic treatment, would improve recipients’ immune responses to vaccines. These helminth infections such as Ascariasis, hookworm and schistosomiasis are rampant in developing countries, especially Sub-Saharan Africa. This remains a major health concern as helminth infections, especially those that remain untreated, would reduce efficacy of vaccines thus posing a serious risk of increased infections leading to outbreaks in these areas. The effects helminths have on the immune responses elicited by vaccines still remain unclear as relatively little information is available. This could be due to lack of controlled experiments involving animal models, especially the Non-human primates. This review compiles information from a number of peer reviewed articles and aims to explain the host-parasite interaction, the immune response generated and summarizes how helminth infections affects the immune responses of various vaccines. This may provide a greater understanding of the strategies helminths use to evade the immune system which in turn affect the immune responses elicited by vaccines.