Age-appropriate vaccination and its determinants among children

Background: Administration of vaccines at recommended ages and according to recommended intervals between doses of multi-dose antigens provides optimal protection, ultimately reducing the possibility of propagating the transmission of vaccine-preventable diseases. A sizable discrepancy in the median age at vaccination has been shown in Nigeria. This study assessed age-appropriate vaccination and related factors among children aged 0–23 months attending immunization clinics in the Kano metropolis. Materials and Methods: An adapted and pretested semi-structured interviewer-administered questionnaire was used to obtain information from a cross-section of 384 pairs of mothers/babies who presented to the immunization clinics of selected primary health centers within Kano metropolis. Results: The median ages at vaccination were 13, 49, 91, 122, and 282 days for BCG, pentavalent-1, pentavalent-2, pentavalent-3, and measles antigens, respectively. Proportions of children who had received age-appropriate vaccines were 83.8%, 81.6%, 64.9%, 60.4%, and 40.3% for BCG, pentavalent-1, pentavalent-2, pentavalent-3, and measles vaccinations, respectively. Children who were 4 months or older were 80% less likely to be age-appropriately vaccinated compared to those 3 months or younger (adjusted odds ratios [aOR]: 0.2, 95% confidence interval [CI]: 0.1–0.7). Furthermore, children with a previous experience of an adverse event following immunization were 50% less likely to be age-appropriate for the index vaccination (aOR: 0.5, 95% CI: 0.3–0.9). Conclusion: Many children in the Kano metropolis were not age-appropriately vaccinated. The measles vaccine had the least proportion of age-appropriately vaccinated children. Sensitization and health education of caregivers on timely vaccination cannot be overemphasized.