Background: Immunization is one of the most powerful and cost-effective public health interventions. Most vaccines in the immunization schedule require two or more doses to trigger adequate immune response; appropriate timing, proper interval between vaccine doses, and completion of all vaccine doses are important to attain optimal protection.
Objective: To evaluate and identify factors associated with the timeliness of vaccine doses; assess the interval between vaccine doses; and identify missed opportunities among children aged 12 to 23 months.
Methods: A cross-sectional descriptive study was conducted that employed the 30 by 10 modified WHO immunization coverage cluster sampling technique. Considering pastoral and semi-pastoral areas, a total of 60 clusters with a sample of 600 children aged 12 to 23 months and mothers/caregivers were included. Data were collected using smartphones loaded with the Open Data Kit (ODK) system and exported to STATA 12.0 for data description and analysis.
Results: The response rate was 97%, with 54.8% of the sample from pastoral areas. About 51% of the respondents were Muslim, 68% had no education, and 67% were aged 30 or above. More than one fifth (21.9%) of children received at least one vaccine dose earlier than the recommended minimum age. Nearly half (47.7%) of children received at least one subsequent dose earlier than an interval of four weeks. The overall rate of missed opportunities was 42.7%, which was higher in pastoral (61.4%) compared to semi-pastoral areas (30.9%) (P <0.001). Children from pastoral areas had a higher rate of missed opportunities compared to children from semi-pastoral areas (OR=4.05; 95% CI: 2.28-7.22); and children from mothers/caregivers aged 30 or above had a higher rate of missed opportunities than mothers aged <30 (OR=1.89; 95% CI: 1.32-3.13).
Conclusions: The study identified high proportions of children who started vaccination earlier than the recommended age (later for the first dose of Oral Polio Vaccine (OPV0)). In addition, multiple vaccine doses were administered before the minimum interval of four weeks. Children in pastoral areas have higher rate of missed opportunities compare to children in semi pastoralist and pastoralist areas for vaccines with same schedule.
Recommendations: Strong interpersonal communication between mothers and vaccination providers is vital for the timely administration of vaccines. Emphasis should be placed on regular supervision and periodic in-service training of health workers to practice timely vaccine commencement, and maintain proper intervals between doses. Immunization service providers should give all the recommended vaccines with same schedule to reduce rate of missed opportunities. [Ethiop .J. Health Dev. 2019; 33(Special issue):00-00]
Key words: Vaccination timing, interval between doses, pastoralist, semi-pastoralist, Ethiopia, CORE Group Polio Project