Mobilizing voices for science to promote trust in vaccination: the health ambassadors multi-site randomized controlled trial

INTERVENTION: This study targets adults residing in catchment areas (clusters) of selected urban health facilities in Côte d'Ivoire, Malawi, Senegal, and Zimbabwe where vaccines, including those for COVID‐19, Typhoid, HPV and Hepatitis B are available. In each of the four countries ‐ Côte d'Ivoire, Malawi, Senegal, and Zimbabwe ‐ the researchers selected 32 health centers in densely populated urban areas based on (1) the availability of the priority vaccines for each country and (2) making sure that the health facilities are at least 4 km apart to avoid spillovers. In each cluster, the researchers obtained approval from the relevant health authorities to proceed with field activities. Field enumeration staff (separate from the Health Ambassadors) operate under the research team’s supervision to select 24 households to be surveyed within each cluster. The household selection process is as follows: 1. Using Google Maps, the researchers plot the GPS coordinates of the focal health facility in the cluster and then create a circular buffer of 1 km around that coordinate point. 2. They stratify the circular area into si Xevenly spaced concentric bands of increasing distance to the health facility. 3. They randomly sample a geolocated point within each band. 4. Using Google Maps, the researchers identify the residential structure (house, flat, etc) nearest to each of those sampled points. Enumerators are instructed to select one household from within this structure. 5. Proceeding 50 m along the same side of the street in either direction from the initial residential structure (turning the corner if necessary), select si Xadditional residential structures that are spread evenly between the first selected residential structure and the ends of the 50 m segment. (The 50 m distance will be CONDITION: Trust in vaccination among adults eligible for vaccination but who were not vaccinated for COVID‐19 ; Infections and Infestations PRIMARY OUTCOME: Vaccine trust measured using the Vaccine Trust Index (VTI) for COVID‐19 and other targeted vaccines at baseline prior to any intervention and then at endline, which will occur within 1 month after the end of the six‐week intervention implementation period. SECONDARY OUTCOME: Vaccine uptake measured for each vaccine and each household member using:; 1. Household member’s verbal affirmation of receiving the vaccination (yes or no); 2. Whether the household member provided documentation of vaccination (e.g. their vaccination card) (yes or no); Measured at baseline prior to any intervention and then at endline, which will occur within 1 month after the end of the 6‐week intervention implementation period. INCLUSION CRITERIA: Eligible participants are adults (at least 18 years old) who live in households located within the catchment areas of health facilities where the Health Ambassadors will be based (the catchment area is a 1km circular buffer surrounding the health facility) and who meet all the following three conditions: 1. At least one adult member of the household has not been vaccinated against COVID‐19 at the baseline survey. 2. The head of the household or their representative consents to carry out the survey at the baseline and endline survey. 3. The head of the household or their representative consents to be contacted again by the research team.