Fig. 4

Coefficient estimates of covariates associated with average egg reduction rates among children infected with schistosomes following treatment with praziquantel. Panels a and b depict coefficients estimated from the marginal models fitted to the data on, respectively, Schistosoma haematobium and S. mansoni egg counts measured from children before and after treatment with praziquantel. The coefficient point estimates (black circles) indicate the multiplicative change (risk ratio, RR) in egg counts after treatment in a particular covariate group compared to the change after treatment in the reference group. Hence, a RR <1 is associated with an increased efficacy and a RR >1 is associated with a decreased efficacy (compared with the reference group). Error bars depict 95 % confidence intervals (CIs). A covariate is deemed to exert a statistically significant effect only when its CI does not cross the vertical grey line at RR = 1. For example, older school-aged children (SAC) infected with S. haematobium are associated with a statistically significant decrease in efficacy (RR >1) compared to younger SAC