Evaluating Coverage and Compliance of a School-Based Schistosomiasis Mass Drug Administration on Unguja Island, Zanzibar

Schistosomiasis persists as a public health burden in sub-Saharan Africa, including Zanzibar. School-based mass drug administration (MDA) is central to control, but its effectiveness relies on high coverage and compliance. Performance data for such campaigns on Unguja Island are scarce. This study evaluated the coverage and compliance of a school-based schistosomiasis MDA campaign on Unguja Island, Zanzibar. Its primary objectives were to quantify the proportion of targeted school-aged children who received praziquantel (coverage) and who completed the full, observed treatment (compliance). A cross-sectional cluster survey was conducted after an MDA campaign. A representative sample of primary schools was selected using probability proportional to size sampling. Data were collected through structured interviews with headteachers and direct observation of treatment registers. Coverage was calculated as the number of children treated divided by total enrolment. Compliance was defined as the proportion of treated children who swallowed all tablets under observation. The survey achieved a 98% response rate from selected schools. Programme coverage was 87.4% among enrolled children. Directly observed full compliance was lower, at 76.2%. Key reasons for non-compliance included absenteeism on treatment days and taste aversion to the tablets. The campaign achieved high coverage but suboptimal compliance, revealing a gap between drug distribution and complete ingestion. Reported coverage figures may therefore overestimate the actual chemotherapeutic impact at the population level. Programme managers should strengthen strategies for directly observed treatment, including dedicated follow-up for absentees. Further qualitative research is needed to understand and address barriers to tablet swallowing. Integration with other school health programmes could improve efficiency and uptake. schistosomiasis, mass drug administration, praziquantel, coverage, compliance, school-based health, Zanzibar. This study provides critical empirical evidence on the implementation gap between coverage and compliance in a school-based schistosomiasis MDA, offering practical insights for strengthening control programmes in similar settings.