Sampling strategy
This qualitative study is embedded within a larger multi-country, cluster randomized trial involving 30 communities (villages) in rural areas of Bangladesh (districts of Tangail and Munshiganj, Pakistan (district Thatta), and Sri Lanka (district Puttlam). In each country, the unit of randomization was a cluster defined by 250–300 households defined by local administration according to CHW catchment area (each cluster of households served by one to two CHWs). The post- implementation qualitative study was undertaken in 5 intervention clusters in each country that were randomized to multicomponent intervention versus usual care, as explained in the COBRA-BPS protocol paper [The sampling strategy was purposive and based on sex, age-group, and those who had already been recruited in the trial in randomly selected clusters.The Ethics Review Committees at icddr,b, Bangladesh (reference PR-15104), Aga Khan University, Pakistan, (reference 3833-CHS-ERC-15), University of Kelaniya, Sri Lanka (reference p/179/11/2015), London School of Hygiene & Tropical Medicine, UK (reference 10361), and Duke-NUS Medical School, Singapore (reference B-15-253) approved the study. The trial is registered at ClinicalTrials.gov. NCT02657746. The authors vouch for the completeness and accuracy of data, and the fidelity of the trial as reported.