Authors

Discussion

What happens if individuals are infected with parasites when they are vaccinated? I conducted a meta-analysis to explore this question, and found that, in general, parasites tend to interfere with immunisation: individuals infected with helminths, protozoa, and viruses have worse immunisation outcomes compared with uninfected individuals. I also found that chronic helminth infections tend to result in worse immunisation outcomes than acute helminth infections, and that vaccines that are thymus-dependent are more susceptible to parasite interference than thymus-independent vaccines.  In parallel to the meta-analysis, I have begun to investigate parasite-vaccine interactions in the field. Raccoons are one of the main vectors of rabies in the United States and are currently subject to a federal vaccination campaign that aims to eliminate raccoon rabies via an oral vaccine. My field research suggests that raccoons that are infected with gastrointestinal nematodes are less likely to become immunised by the rabies vaccine compared with uninfected raccoons. In a cross-sectional survey following vaccine baiting, only 22% of nematode-infected worms had antibodies to rabies, compared with 31% of uninfected raccoons, and nematode infection status was a significant factor in a general linear model of rabies serostatus.