Impact Evaluation of a Community Engagement Intervention for Improving Childhood Immunization Coverage in Rural Assam, India: A Cluster Randomized Controlled Trial

Background: For childhood immunization, community engagement interventions can potentially address demand-side barriers to achieving immunization coverage targets, while also mobilizing the community to advocate for better service delivery. However, high-quality evidence that can causally relate such interventions to increased immunization coverage is scarce. We evaluated the impact of a community engagement intervention on childhood immunization coverage in rural India. Methods and findings: The community engagement intervention, referred to by the acronym SALT (Stimulate, Appreciate, Learn, Transfer), is a complex intervention involving an iterative process of multiple steps and continued engagement with the community. To evaluate the SALT intervention, we conducted a cluster randomized controlled trial in 196 villages spread across 3 districts in rural Assam, a state in the northeast region of India. The villages in the intervention group (n=97) received the SALT intervention for about one year along with routine immunization services and the villages in the control group (n=99) received only routine immunization services. The primary evaluation outcomes were full immunization, defined as one dose of Bacillus Calmette–Guérin vaccine, three doses of oral polio vaccine, three doses of diphtheria- pertussis-tetanus (DPT) vaccine or Pentavalent vaccine and one dose of measles vaccine, in children 12- 23 months old, and three doses of DPT or Pentavalent vaccine in 6- 23 months old children. To gather information on evaluation outcomes, we conducted cross- sectional household surveys at baseline and after 22 months at endline, in the 196 villages. We interviewed mothers with a 6-23 months old child in a random sample of households in eachvillage. In our analyses, we followed the intention-to-treat principle and used mixed-effects models to account for clustering. At endline, a total of 2,907 mothers were interviewed resulting in a median number of 15 (interquartile range (IQR)= 0) 6-23 months old children and 10 (IQR=2) 12-23 months old children from each village in both the intervention and the control groups. There was no difference between the two groups in the proportion of 12-23 months old children receiving full immunization (OR=0.98, 95% CI: 0.71 – 1.36) or in the proportion of children receiving three or more doses of DPT or Pentavalent among 6-23 months old children (OR=1.01, 95% CI: 0.76 – 1.35). Conclusions: The intervention was not found to be effective in increasing childhood immunization coverage in our study. After baseline survey, we noted that the vaccination coverage in the three districts was substantially higher than previously reported in national surveys which were used in designing the trial. The higher coverage rates were most likely due to widespread implementation of a supplementary immunization programme led by the Government of India prior to this study. We do not know whether selecting study sites with a lower vaccination coverage rate at baseline or having a more targeted approach in implementing the intervention would have resulted in a positive impact.