Household-based Survey of Diphtheria Vaccination in Osogbo Vis-à-vis 2023 Diphtheria Outbreak in Osun State, Nigeria: A Snapshot Assessment

Abstract

Abstract Background: Inadequate immunisation with diphtheria vaccine might lead to diphtheria outbreak, which actually occurred in 2022–2023 in Nigeria. We conducted a snapshot assessment of DPT/PENTA vaccination history to determine complete diphtheria vaccination coverage, dropout and zero-dose rates and associated factors among children born between 1 January 2007, and 10 February 2023, and living in Osogbo and two bordering local government areas (LGAs), Osun State. Materials and Methods: This was a household-based survey; with ethical approval, 250 households in five clusters were contiguously selected for face-to-face interviewer-based interaction using semi-structured questionnaires. Consenting caregivers of children in each household provided pertinent socio-demographic and diphtheria vaccination data. Results were analysed using the Mann–Whitney U -test and Binary Logistic Regression. Results: A total of 234 (93.6% [95% confidence interval (CI): 89.9%–96.0%]) children had vaccination cards; seven cards had no record of DPT/PENTA vaccination. Full diphtheria vaccination coverage (81.2% [95% CI: 75.9%–85.6%]) was acceptably high, with statistical association of five caregivers’ and two children’s variables. The PENTA1 to PENTA3 dropout rate (10.3% [95% CI: 6.9%–14.9%]) was higher than the WHO recommended threshold, indicating poor utilisation of immunisation services by the caregivers; one factor each of caregivers and children were associated with the dropout rate. The proportion (9.2% [95% CI: 6.2%–13.4%]) of children without evidence of PENTA vaccination (zero-dose rate) was also considerable, indicating lack of access of the children to immunisation services; three caregivers’ factors were associated with the zero-dose rate. Conclusion: The partially immunised/high dropout rate (incompletely immunised) and the 23 zero-dose children (non-immunised) could initiate diphtheria outbreak; while the high full coverage would make it low as observed in Osun State in 2023. The State’s health services need to increase efforts to ensure better utilisation of immunisation services and increase enlightenment campaigns on diphtheria and other childhood immunisations in the LGAs.