At the heart of control and elimination programs to combat neglected tropical diseases (NTDs) amenable to preventive chemotherapy is the successful implementation of annual mass drug administration (MDA), a large-scale effort to distribute safe and effective treatments to entire at-risk populations in an endemic area. The importance of achieving effective MDA coverage rates cannot be overstated. For example, when MDA for lymphatic filariasis achieves effective annual coverage (defined as 80% of eligible population, or 65% of total population), transmission of the disease can be interrupted after 5-6 years of mass treatment, bringing much needed relief to endemic communities. With support from USAID’s Act to End Neglected Tropical Diseases | West program (Act | West), Sierra Leone’s national NTD Program (NTDP) is targeting four NTDs that cause serious illness, blindness, and disability—lymphatic filariasis, onchocerciasis, schistosomiasis, and soil-transmitted helminthiasis—for elimination or control.
MDA monitoring is critical to assessing, improving and maintaining effective coverage, without which disease transmission will persist. MDA monitoring tools can help assess coverage in real-time, identify areas where coverage is below targeted thresholds, and validate reported coverage results after MDA (if using an end-process tool). Monitoring provides insights into areas where the NTDP can tailor approaches, such as strengthening training or diversifying social mobilization, and identifies weaknesses in the supply chain and in service delivery to hard-to-reach communities, to guide modifications during implementation. To this end, two MDA monitoring methods have been used in Sierra Leone: independent monitoring and the supervisor’s coverage tool.
Independent monitoring versus the supervisor’s coverage tool
Independent monitoring (IM) was developed in 2010 to assess MDA coverage in Sierra Leone’s Western Area, where the population had greatly surpassed projections from the 2004 census. It was modelled upon the approach used in vaccination campaigns, with a basic sampling methodology of 30 randomly (or purposefully) selected sites x 30 randomly (or conveniently selected) respondents. In Sierra Leone, equal numbers of men and women are sought for each site within communities (at markets, transport terminals, or entertainment centers/cafes, for example) and within households. This purposeful sampling methodology is helpful where census data is in question, populations are migratory or unstable—perhaps due to insecurity or economic or sociopolitical factors—and when local knowledge of the context can be leveraged.
Independent monitors are typically recruited from local universities and then trained on the IM methodology and tested by staff from the NTDP and the Act | West program. The use of independent monitors who do not have ties to the NTDP ensures the objectivity of the findings. With both IM and the supervisor’s coverage tool, a questionnaire is used to conduct interviews with community members and findings are recorded on a tally sheet.
IM has two phases: in-process and end-process. In-process IM is conducted during the MDA to help identify challenges and coverage gaps, thereby allowing course-corrections. Around the capital in the Western Area, Independent monitors debrief with Ministry of Health staff daily and devise plans to correct problems overnight. In the provinces, monitors record their findings via a mobile health (mHealth) platform, which are then reported to the NTDP for corrective action.
End-process IM occurs within one week of the MDA campaign to validate reported coverage. A final debriefing session is held to discuss lessons learned, program coverage rates (which can be compared to reported epidemiological coverage rates), and opportunities for improvement in the next MDA campaign. If coverage gaps are identified in a community, the drug distribution period is extended and tailored to address the challenge. For example, in the recent MDA in the Western Area, monitoring reports showed that some villages had low coverage because many male fishermen were out at sea during the MDA. To address the problem, drugs were distributed during the early morning and late evening hours, which enabled the NTDP to reach this population without interfering with their work schedules.
The supervisor’s coverage tool (SCT) is an in-process tool that is designed to quickly identify areas with low coverage that need additional support for MDA. The sampling methodology is similar to Lot Quality Assurance Sampling (LQAS), whereby supervisory areas are defined and subdivided into ‘lots’. These lots are then evaluated on whether they have achieved a pre-determined target threshold. Within each lot (of no more than 5,000 individuals), 20 non-overlapping communities are randomly selected and mapped. Then, households and individuals are randomly selected and interviewed. Finally, the MDA coverage rate in each lot is classified as ‘good,’ ‘cannot conclude,’ or ‘low coverage’. When using the SCT (and unlike with IM), it’s important to have reliable population data so that new communities (enumeration areas) are not missed.
Adapting SCT in Sierra Leone
Sierra Leone’s post-war and Ebola contexts have had significant consequences for the enumeration of communities. Census data have been rendered unreliable by displaced persons, employment-seeking migration, and disease risk. To this end, purposeful selection has been used for IM in communities known to be hard to reach or to have had recent population changes or historical difficulties in providing effective MDA or vaccination coverage. Because IM is purposefully focused towards vulnerable communities, which are likely to have low coverage due to context-specific circumstances, the coverage rates reported through IM cannot be directly compared to the overall, district-level MDA coverage rate.
Like IM, the SCT can help detect issues related to low coverage, such as poor compliance or performance of community drug distributors (CDD). The tool can also be used to identify sub-districts in need of additional treatments. While SCT requires more reliable population data for planning, it is a more rigorous methodology than IM due to the use of a randomized sampling methodology.
Under Act | West, Sierra Leone has begun to use independent monitors to monitor MDA coverage using the SCT methodology. While SCT is traditionally implemented by local CDD supervisors, the experience in-country has been that independent monitors are more effective, given that human resources within the health sector are over-stretched during campaigns, and the strict methodology can be challenging.
Using independent monitors to implement SCT has enabled Sierra Leone to reap benefits from both methods, allowing context and local knowledge to drive the monitoring approach. Through its efforts to identify communities with low MDA coverage and its commitment to working with NTD partners like Act | West to provide these communities with supplementary support (which may require additional funds and extend MDA beyond previously agreed timelines, but is essential to achieving effective coverage), Sierra Leone has demonstrated its commitment to beating NTDs once and for all.