BACKGROUND: Every year, immunization prevents about 4-5 million child fatalities from vaccine preventable morbidities. Conversely, in Ethiopia, achieving full coverage of vaccination has continued to be challenging. Socio-demographic, caregivers and child related factors determine vaccination coverage. Therefore, this study aimed to find out recent coverage, trends in coverage, and its predictors in eastern Ethiopia. METHODS: A population-based longitudinal study design was conducted among 14,246 children aged 12-24 months from 2017 to 2021 in Kersa Health and Demographic Surveillance System site (KHDSS). The data were collected from caregivers of the child by face to face interview. Multinomial logistic regressions were used to identify predictors of vaccination. The association between vaccination coverage and its predictors was presented by adjusted odds ratio with 95% confidence interval. A p-value of <0.05 was used to establish statistical significance. RESULTS: From the 14,198 included children, only 39% of children were fully vaccinated, with highest proportion in 2020 (45%) and lowest proportion in 2019 (32%). In comparison to fully vaccinated, being partially vaccinated was positively associated with older maternal age, rural residence, unemployment, rich wealth index, no antenatal care, facility delivery, and birth order whereas negatively associated with semi-urban residence. In compared to fully vaccinated, being not vaccinated was positively associated with older maternal age, rural residence, maternal education, unemployment, and no antenatal care whereas negatively associated with semi-urban residence, poor wealth index, multipara, grand multipara, and facility delivery. CONCLUSION: Less than two-fifths of children aged 12 to 24 months were fully vaccinated. Socio-demographic factors and maternity care utilization were found to be predictors of vaccination coverage. Therefore, strategies that emphasize women's empowerment in terms of education, economy, and employment status, and enhancing maternal healthcare utilization may improve vaccination coverage.
