Determinants of default to fully completion of immunization among children aged 12 to 23 months in south Ethiopia: unmatched case-control study

Introduction Immunization is a cost effective interventions of vaccine preventable disease. There is still, 2.5 million children die by vaccine preventable disease every year in developing countries. In Ethiopia, default to fully completion of child immunization is high and determinants of default to completions are not explored well in the study setting. The aim of the study was to identify determinants of default to fully completion of immunization among children between ages 12 to 23 months in Sodo Zurea District, Southern Ethiopia. Methods Community based unmatched case-control study was conducted. Census was done to identify cases and controls before the actual data collection. A total of 344 samples (172 cases and 172 controls) were selected by simple random sampling technique. Cases were children in the age group of 12 to 23 months old who missed at least one dose from the recommended schedule. Bivariable and multivariable binary logistic regression was used to identify the determinant factors. Odds ratio, 95%CI and p - value less than 0.05 was used to measure the presence and strength of the association. Results Mothers of infants who are unable to read and write (AOR=8.9; 95%CI: 2.4, 33.9) and attended primary school (AOR=4.1; 95% CI:1.4-15.8), mothers who had no postnatal care follow up (AOR=0.4; 95%CI: 0.3, 0.7), good maternal knowledge towards immunization (AOR= 0.5; 95% CI: 0.3, 0.8) and maternal favorable perception towards uses of health institution for maternal and child care (AOR= 0.2; 95% CI: 0.1, 0.6) were significant determinant factors to default to fully completion of immunization. Conclusion Working on maternal education, postnatal care follow up, promoting maternal knowledge and perception about child immunization are recommended measures to mitigate defaults to complete immunization.


Introduction
Immunization has become the most effective public health measure for the control of infectious vaccine preventable disease and one of the best tools to decrease child mortality and morbidity [1]. Despite their impact, vaccines have generally received less attention than drugs, but the vaccine landscape is shifting, and new opportunities, challenges, and debates have pushed vaccines to the center of global health discussions [2]. Incomplete immunization can put children at greater risk of acquiring a disease and partial immunization coverage against vaccine preventable diseases is a significant public health challenge in developing countries [3].
Immunization averts an estimated 2 to 3 million deaths every year in all age groups from diphtheria, tetanus, pertussis (whooping cough) and measles worldwide. Africa and Southeast Asia are regions most affected by the problem of vaccine preventable disease of which more than 70% of these children live in 10 developing countries and South Africa including Ethiopia [4].

According to Medicines Sans Frontiers (MSF) Access Campaign-
Oxfam 2010 Vaccine -Report, there are multiple suggested factors that make delivering vaccines to children in developing countries makes difficult; lack of research and promotion for better-adapted and needed vaccines, and fragile health systems with corresponding health personnel shortages [2]. Vaccination is one of the indicators used to monitor progress towards the achievement of Millennium Development Goal (MDG) goal 4, i.e. the reduction of child morbidity and mortality [5]. Ethiopia has been implementing different strategies by considering it as one of the most costeffective measures to reach 90% coverage at the end of the implementation of the program. However, the national vaccination coverage still remains at 24% in 2011with huge variation among regions and place of residence within the country [5 -7]. Previous studies done in Ethiopia [8,9] indicated that the main factors affecting to complete immunization are multiple such as age of the mother, parents education, knowledge about immunization, antenatal care (ANC) and postnatal care (PNC), marital status, mother's occupation, sex of the child, birth place, birth order, place of residence and distance to health intuitions. Even though there is a consensus about the above problems to the contribution of low coverage of vaccination, the problem still persisted with much little improvement posing a challenge to the country health care delivery system [5,6,8]. Therefore studying the determinants of incomplete immunization allows for effective implementation of policy where there is a high rate of defaulter. technique was used to select the study participants. The district was classified in to two strata; urban and rural. Then two urban and three rural kebeles were randomly selected. For the purpose of this study, census was done to identify the eligible mothers which was start from north side of the kebele goes by serpentine motion to end of total proportionally identified households. During the census, cases and controls are identified based on self report of care takers  Table 2).

Discussion
Immunization is one of the most powerful and cost-effective of all health interventions. It prevents debilitating illness and disability, and saves millions of lives every year around the world. Vaccines have the power not only to save, but also to transform, lives -giving children a chance to grow up healthy, go to school, and improve their life prospects [9,10]. Coherent with the previous studies [8,[10][11][12][13][14]; educational status of the mothers is the determinant factors to complete fully immunization in the present study. This is due to the fact that educated mothers could have better knowledge and decision making skill on different issues of the child health including timing on immunizing their children as compared to illiterate mothers. Children whose mothers had PNC follow up after birth had decreased their chance by 60% to default to complete immunization than mothers who didn't follow up of PNC which is supported with the previous study carried out in Ethiopia [15]. This is due to the fact that mothers who had PNC follow up could Page number not for citation purposes 4 appreciate the advantage of timely and fully completed immunization children for the development of their infants.
This study also revealed mothers who had good knowledge towards immunization were 50% less likely to default to complete immunization in line with the previous studies done in Ethiopia [15,16]. This is may be due to the fact that mothers' who had good knowledge towards immunization are not be a house wife's employee and return back to their job before completing the immunization schedule of their infants. In Ethiopia maternity leave for governmental employee is only three months that could have been also the reason to default to complete their infant's immunization.
Moreover, mothers of infants with good perception towards uses of health service were 80% less likely to default to complete immunization than those mothers who had unfavorable perception towards uses of health service. This finding is in agreement with previous studies conducted in Ethiopia [8,15]. The explanation related to inaccessibility of health institutions and inadequate health professionals may be the possible cause to default to complete. The potential limitation of our study was first, recall bias where mothers may difficult to remember the immunization status of their children, total doses of vaccine the child took and misclassification of cases and controls. Second, the study was not supported by qualitative study to explore reasons of mothers/caretakers to default to complete.

Conclusion
The result of this study provided variables such as; un able to read and write and attended primary school in educational status, had not postnatal follow up, maternal knowledge towards immunization, maternal perception towards uses of health service were independent predictors of default to complete immunization. Improve maternal education; promote health education, implementation of health institution counseling and support and strengthening postnatal care services is recommended as inevitable measure to curb poor immunization practice in the study setting.
What is known about this topic  Fully vaccination coverage is still below the goal in  This study also support mothers of children who had good knowledge on vaccine preventable disease with favorable health seeking behavior helps to achieve fully vaccination coverage goal.

Competing interests
The authors declare no competing interests.

Authors' contributions
AG designed the study, and performed the statistical analysis, AF and DN participated in the thesis report and manuscript writing and YA and EG drafted the manuscript. All authors contributed to the data analysis and read and approved the final thesis report and manuscript.
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Acknowledgments
We would like to thank Central Statistical Agency (CSA) of Ethiopia for the financial support to conduct this study. We also would like to thank the respondents.