Partial vaccination and associated factors among children aged 12–23 months in eastern Ethiopia

Background: Vaccine prevents about 2–3 million deaths from vaccine-preventable diseases each year. However, immunization coverage in Ethiopia is lower than the herd immunity level required to prevent the spread of all vaccine-preventable diseases. Thus, this study aimed to assess the partial immunization and associated factors among 12–23-month-old children in Eastern Ethiopia. Method: A community-based cross-sectional study design was carried out among 874 randomly selected mothers/caregivers of children aged 12–23 months. A structured questionnaire was adapted and data were collected through face-to-face interviews and review of vaccination cards. Data were coded and analyzed using the Stata version 14 software. A binary logistic regression model was utilized to identify the determinant factors. The predictor of partial immunization was presented by an adjusted odds ratio with a 95% confidence interval. A p-value of < 0.05 was used to establish statistical significance. Result: The prevalence of partial immunization was 31.4% (95% CI: 28–35). The dropout rate between the first and third pentavalent vaccine was 17%. Being female child [AOR = 0.73, 95% CI: 0.52–0.95], 18–20 month child [AOR = 1.6, 95% CI: 1.1- 2.4], the child born to mothers who heard about vaccination [AOR = 3.9, 95%CI: 1.92- 8.01], a child born to mother who did not receive immunization counselling [AOR = 1.65, 95%CI: 1.15–2.36], and child whose mother walk 15–30 min, 31–60 min, and > 60 min to reach nearby health facilities [AOR = 1.94, 95% CI: 1.1–3.45], [AOR = 4.5, 95% CI: 2.47–8.15], and [AOR = 3.45, 95% CI: 1.59- 7.48] respectively were factors significantly associated with partial vaccination. Conclusions: The prevalence of partial immunization is high compared to other studies. As a result, to decrease the proportion of defaulters and to increase immunization coverage, maternal health care utilization like antenatal care follow-up and mother knowledge about the importance of the vaccine need to be sought cautiously. A community-based cross-sectional study was conducted in Haramaya District, East Hararge zone; Oromia Region in Ethiopia from January 1st to January 30, 2021. The district is 506 km away from Addis Ababa, the capital of Ethiopia. Haramaya district has 2 urban and 32 rural kebeles. According to the 2007 national census, the total population of Haramaya district is 304, 849; of which 152,119(49.9%) and 152,729(51.01%) were males and females respectively; with 9,816 (3.22%) 12 to 23-month-old children. There are 8 health centers, 38 health posts, and 13 low-level private clinics in the district (Haramaya administrative health office report for 2018). Mothers/caregivers with children aged between 12 to23 months who lived in Haramaya district during the study period comprised the study population. Mothers who had an alive child aged between 12–23 months and lived in the area were eligible. The sample size was calculated by using a single population proportion formula with assumptions of confidence level at 95% = 1.96, a margin of error (d) = 0.03, and a proportion of children aged 12–23 months with immunization coverage (P = 0.383) was taken from a study conducted by Tamirat, K.S and Sisay M.M [14] and by adding 5% non-response rate and design effect 1.5, the final sample size became 892. From 34 kebeles of Haramaya district, 5 of them were selected randomly. There were 7675 households in those five kebeles. The calculated sample size (892) was then allocated proportionally to the selected kebeles based on their population (number of mothers/caregivers). Individual study participants were chosen at random from each kebele using a simple random sampling technique. For households with more than one eligible member, an interview was conducted by selecting one woman through a lottery method. The data were collected using a structured questionnaire adapted from the Ethiopian demographic health survey (EDHS [19] and previous literature [20]. It is divided into five sections: socio-demographic data, vaccination knowledge, maternal health care utilization, access and quality of vaccination services, and child vaccination. The questionnaire was written in English, translated to the local languages (Afan Oromo and Amharic) in the study area, and then translated back to English to ensure consistency. Five nurses collected data through face-to-face interviews. Vaccination data were collected from the child’s immunization card, or through an interview if the immunization card was not accessible. Where vaccination card was not accessible, confirmation was done by observing BCG scar. Data collectors and supervisors were trained on how to ask and fill questions, how to select households and children, and how to approach mothers/caregivers. Before the actual data collection, the questionnaire was pre-tested on 5% of non-selected households. The completeness of filled questionnaires was verified. Twelve to twenty-three months old child who received at least one vaccine, but not all the EPI vaccines. In this study, those children who belong to defaulters/do not belong to fully vaccinated were leveled as partially vaccinated were as those children not belongs to the above definition were leveled as not partially vaccinated. A 12–23 months old child who received one dose of BCG and measles, three doses each of the Pentavalent, four doses of OPV, three doses of PCV, and two doses of Rota vaccine before his/her first birthday. A 12–23-month-old child who did not receive any of the EPI vaccines. The vaccination coverage calculated with numerator based only on mothers/caregivers’ reports. Represent the percentage of a target population that has been vaccinated. Coverage is usually calculated for each vaccine and the number of doses received. It is, therefore, the percentage of children within the target population who received vaccinations against specific vaccine-preventable diseases by a certain age and who were reported and documented. Is the rate difference between the initial vaccines (BCG or Pentavalent I) and the final vaccines (Pentavalent III or Measles). BCG to Measles dropout rate: the percent of children vaccinated for BCG who don’t receive measles vaccine. Pentavalent I to Pentavalent III dropout rate: the percent of children vaccinated for Pentavalent I, but who did not receive Pentavalent III. Knowledge of mothers/ caregivers on immunization were measured through 5 knowledge-related questions and the correct answer was level as 1 and the incorrect answer is leveled as 0 and the result was described. The data were coded, cleaned, edited, and entered into Epi data statistical software version 3.1 and then exported to STATA version 14 for analysis. Summary statistics were presented with percentages, mean, standard deviation, median and interquartile range. Binary logistic regression was used to find out predictors of vaccination status. The outcome variable was dichotomized into “Yes (partially vaccinated)” and “No (not partially vaccinated)”. Bivariate analysis and multivariate analysis were done to see the association between each independent variable and partial vaccination by using binary logistic regression. Variables with p-values less than 0.25 in the bivariable analysis were selected for further inclusion in the multivariable model. The multi-co-linearity test was carried out to see the correlation between independent variables by using the standard error (standard error > 2 was considered as suggestive of the existence of multi-co-linearity). The association between outcome and predictors was reported by AOR with a 95% confidence interval. P-value less than 0.05 was considered as a cut-off point for statistical significance. Likewise, after fitting the model goodness of the final model was checked by using the Hosmer- Lemeshow test. The Hosmer–Lemeshow statistic indicates a good fit at a p-value of 0.05 or greater. Ethical clearance to conduct this study was obtained from Haramaya University, College of Health and Medical Sciences, Institutional Health Research Ethics Review Committee (HU-IHRERC). A permission letter was obtained from the district administration and district health office. Informed, voluntary, written, and signed consent was obtained from individuals that were going to be involved in the study, following an explanation about the purpose of the study, risk, and benefit. Confidentiality was kept throughout the data collection and the entire study period. The right to participate or not to participate in the study was explained to the participants.