Child vaccination timing, intervals and missed opportunities in pastoral and semi-pastoral areas in Ethiopia

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