Abstract
The potential consequences of parasitic infections on a person’s immune responsiveness to unrelated antigens are often conjectured upon in relationship to allergic responses and autoimmune diseases. These considerations sometimes extend to whether parasitic infection of pregnant women can influence the outcomes of responses by their offspring to the immunizations administered during national Expanded Programs of Immunization. To provide additional data to these discussions, we have enrolled 99 close-to-term pregnant women in western Kenya and determined their Schistosoma mansoni and Plasmodium falciparum infection status. At 2 years of age, when the initial immunization schedule was complete, we determined their children’s IgG antibody levels to tetanus toxoid, diphtheria toxoid, and measles nucleoprotein (N-protein) antigens using a multiplex assay. We also monitored antibody responses during the children’s first 2 years of life to P. falciparum MSP119 (PfMSP119), S. mansoni Soluble Egg Antigen (SEA), Ascaris suum hemoglobin (AsHb), and Strongyloides stercoralis (SsNIE). Mothers’ infections with either P. falciparum or S. mansoni had no impact on the level of antibody responses of their offspring or the proportion of offspring that developed protective levels of antibodies to either tetanus or diphtheria antigens at 2 years of age. However, children born of S. mansoni-positive mothers and immunized for measles at 9 months of age had significantly lower levels of anti-measles N-protein antibodies when they were 2 years old (p = 0.007) and a lower proportion of these children (62.5 vs. 90.2%, OR = 0.18, 95% CI = 0.04–0.68, p = 0.011) were considered positive for measles N-protein antibodies. Decreased levels of measles antibodies may render these children more susceptible to measles infection than children whose mothers did not have schistosomiasis. None of the children demonstrated responses to AsHb or SsNIE during the study period. Anti-SEA and anti-PfMSP119 responses suggested that 6 and 70% of the children acquired schistosomes and falciparum malaria, respectively, during the first 2 years of life.
Highlights
There is a concern that children in developing countries do not respond appropriately to standard vaccines given through the expanded program of immunization (EPI), and this is most often discussed in regard to the mother’s parasitic disease status during gestation
The question of whether a schistosome infection impacts vaccine responses continues to be of potential public health importance
It seems that initial responsiveness to hepatitis B vaccine and tetanus toxoid is not impacted in young adults, but that the levels of their responses tend to wane earlier if they harbored schistosomes when immunized, perhaps indicating that those with schistosomiasis need to be boosted more regularly to maintain protective levels against these pathogens [29]
Summary
There is a concern that children in developing countries do not respond appropriately to standard vaccines given through the expanded program of immunization (EPI), and this is most often discussed in regard to the mother’s parasitic disease status during gestation. Since vaccine-preventable diseases account for an estimated two to three million deaths in African children each year [7], the extent to which parasitic diseases during gestation influence EPI vaccine effectiveness in neonates could have critical public health consequences. If the helminth infection status of a pregnant woman decreases the effectiveness of current and/ or future vaccine responses of her newborn, anti-helminthic treatment during pregnancy would take on an additional level of public health importance
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