A pragmatic covariate-constrained cluster-randomised controlled trial of hybrid parents and health workers adaptive intervention for optimal (timely, cumulative age-appropriate) community-wide routine childhood immunisation coverage: the AGINTOPIC trial

Introduction Vaccine-preventable infectious diseases (VPDs) covered by routine childhood immunisation programmes are major causes of morbidity/mortality as outbreaks continue to reoccur despite repeated efforts to increase immunisation coverage. This trial aimed at increasing optimal/timely immunisation coverage.Methods The Adaptive Group Intervention for Optimal routine childhood Immunisation Coverage (AGINTOPIC) trial was conducted from 1 June 2022 to 31 May 2023 in Ebonyi state, Nigeria. 16 geographical clusters (where the primary healthcare facilities were providing weekly routine childhood immunisation) were covariate-constrained-randomised (1:1) to control arm (receiving no intervention) and intervention arm (receiving hybrid parents/health workers adaptive engagement to enlighten/facilitate regular communications/working relationships between them regarding optimal immunisation). The primary outcomes included the proportion of children aged 5-9 months who had optimal/timely (cumulative age-appropriate) receipt of every recommended birth to 14 weeks vaccine and the age-appropriate vaccines receipt (receipt timeliness) score. The outcomes were measured via baseline and end-of-study repeated cross-sectional surveys. All analyses were done using a cluster-level method on intention-to-treat basis, and randomisation-based inference was done via adjusted clustered permutation tests (aCPTs) to check the robustness/validity of the main findings.Results A mean proportion of 6.0% (SD 8.1) of children aged 5-9 months in the control arm had optimal/timely receipt of every recommended birth to 14 weeks vaccine, vs 14.3% (11.7) in the intervention arm (adjusted prevalence difference 10.8%, 95% CI 0.8% to 20.9%, p=0.0376, aCPT p=0.0093). The mean age-appropriate vaccines receipt score was 75.1 (17.8) in the control arm, vs 85.5 (9.5) in the intervention arm (adjusted mean difference 9.5, 95% CI 1.0 to 17.9, p=0.0317, aCPT p=0.0155).Conclusions The AGINTOPIC intervention significantly increased the optimal/timely (cumulative age-appropriate) community-wide routine childhood immunisation coverage, and the evidence illuminates the need for the exploration and adaptation of such pragmatic/dynamic/scalable community engagement intervention by routine childhood immunisation programmes in the global efforts to address the recurrent outbreaks of VPDs.Trial registration number ISRCTN59811905.