Timeliness and Completion of Routine Childhood Vaccination and Associated Factors among Children Aged 0–59 Months in Tiko Health District, Southwest Region, Cameroon

Childhood vaccination remains a major public health challenge; global third-dose coverage of the combined diphtheria, tetanus, and pertussis (DTP3) vaccine reached 85% in 2025, yet 13.5 million children remained zero-dose.In Cameroon, national third-dose coverage of the combined diphtheria, tetanus and pertussis vaccine (DTP3) rose to 82.5% in 2024, but sub-national performance remains undocumented: a South-West Region study reported only 47.7% coverage.Whether the Tiko Health District follows this national pattern of declining coverage between initial and subsequent doses had not previously been documented.This cross-sectional study assessed vaccination coverage, timeliness, and associated factors in the Tiko Health District, combining a review of 800 vaccination records and a survey of 604 caregivers of children aged 0-59 months.Age-appropriate vaccination completion was 30.3% (242/800).Coverage declined markedly from 98.6% for Bacillus Calmette-Guerin (BCG) and 76.0% for Pentavalent 1 (Penta1) to 48.1% for Pentavalent 3 (Penta3) and 9.0% for the first measles-rubella (MR) dose.Timeliness remained high for later doses (95.3% for Penta3) despite low coverage.Untimely vaccination was significantly associated with caregivers' lack of schedule knowledge adjusted odds ratio [aOR] = 4.3; 95% confidence interval [CI]: 2.41-7.92),absence of reminders (aOR = 2.2; 95% CI: 1.30-3.66),and age of child under 5 years in the household (aOR = 3.22; 95% CI: 1.26-8.26).Routine immunisation in Tiko shows high initial access but substantial attrition across subsequent doses, indicating that retention, rather than initial uptake, is Tiko's principal challenge.Caregiver knowledge and reminders emerged as the strongest modifiable determinants of timeliness, pointing to clear priorities for improving retention and equity in the district.