Schistosome and malaria exposure and urban–rural differences in vaccine responses in Uganda: a causal mediation analysis using data from three linked randomised controlled trials
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Date
2024-11-21
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The Lancet Global Health
Abstract
Vaccine immunogenicity and effectiveness vary geographically. Chronic immunomodulating parasitic infections including schistosomes and malaria have been hypothesised to be mediators of geographical variations.
We compared vaccine-specific immune responses between three Ugandan settings (schistosome-endemic rural, malaria-endemic rural, and urban) and did causal mediation analysis to assess the role of Schistosoma mansoni and malaria exposure in observed differences. We used data from the control groups of three linked randomised trials investigating the effects of intensive parasite treatment among schoolchildren. All participants received the BCG vaccine (week 0); yellow fever (YF-17D), oral typhoid (Ty21a), human papillomavirus (HPV; week 4); and HPV booster and tetanus–diphtheria (week 28). Primary outcomes were vaccine responses at week 8 and, for tetanus–diphtheria, week 52. We estimated the total effect (TE) of setting on vaccine responses and natural indirect effect (NIE) mediated through current or previous infection with S mansoni or malaria, and baseline vaccine-specific responses.
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Natukunda, A., Nkurunungi, G., Zirimenya, L., Nassuuna, J., Zziwa, C., Ninsiima, C., ... & Walusimbi, B. (2024). Schistosome and malaria exposure and urban–rural differences in vaccine responses in Uganda: a causal mediation analysis using data from three linked randomised controlled trials. The Lancet Global Health, 12(11), e1860-e1870.