Introduction: Immunization is one of the feasible and cost-effective child survival strategies that prevent morbidities and mortalities from vaccine preventable diseases. Despite a continued global effort in providing vaccinations, there are still cases of inadequate immunization coverage especially in low-income countries. With the high under-five mortality in Ethiopia (67 deaths per 1,000 live births), only 38.5% of the children (12 to 23 months) had received all the recommended vaccines. Few studies in Ethiopia have been done on the association of maternal factors with full immunization. Hence, the purpose of this study was to assess factors associated with full immunization coverage among children aged 12 to 23 months in Debre Markos town. 
Methods: A community based cross-sectional study was employed among 389 children aged 12–23 months in Debre Markos town from January 1, 2018 to February1, 2018. Systematic random sampling technique was used to select the study participants. Data was collected using face to face interviewer administered structured questionnaires. Then, the collected data was entered, coded, and cleaned into EPI Data version 3.1 and exported to SPSS version 20.0 for data analysis. Bivariate and multivariate logistic regression was done to assess the association of factors with full vaccination coverage. Adjusted odds ratios with 95% confidence intervals were calculated, and p-values <0.05 were considered to indicate statistical significance. 
Result: This study revealed that full immunization coverage among children aged 12 to 23 months was 76.9%. Full immunization coverage was significantly associated with women’s level of education (AOR=1.2, 95%CI (1.41-2.42), place of delivery of the index child (AOR=3.28, 95%CI (1.38-3.67), maternal knowledge on vaccine and vaccine  preventable disease (AOR=4.12, 95%CI (3.0-10.6) and ANC service utilization (AOR=5.04, 95%CI (1.35-12.06) 
Conclusion: Full immunization coverage among children aged 12 to 23 months in the studied area was low. Maternal education, place of delivery, knowledge and ANC service use were significantly associated with full immunization coverage

Immunization is one of the feasible and cost-effective child survival strategies that prevent morbidities and mortalities from vaccine preventable diseases [1, 2]. It is approximated that every year the life of two and half million under-5 children can be saved with childhood vaccines and a toll of deaths could be averted with increased immunization coverage [3]. With this importance, improving access to and utilization of routine immunization services as a best option is unquestionable. However, one-fifth of the world’s children today – about 20 million infants are not immunized against vaccine preventable fatal diseases. Of nearly 20 million infants who didn’t receive routine EPI service globally in 2017, about sixty percent of these children have been living in ten countries including Ethiopia [4].  As a result, around one to two million children under five years of age died each year from vaccine-preventable diseases [5]. 
With a continued global effort in providing immunizations, the overall coverage in 2018 worldwide was increased to 86% [6]. However, there are still cases of inadequate immunization coverage especially in reaching those at high risk: the poorest, most disadvantaged and remote communities. In addition, the coverage in low-income countries remains significantly below the levels in middle- and high-income countries [7]. In developing countries, increasing access to full immunization service has been a primary concern of public health importance both at global and national contexts. However, meeting high and equitable coverage remains questionable in these countries. Despite the availability of vaccines and the efforts of governments and their partners’ in Sub-Saharan Africa, mortality rate of children under the age of five years remains the highest [8].
Ethiopia is not different for this scenario in that, a substantial number of deaths and morbidities among under fife age children in the country are due to vaccine‒preventable diseases. A country in the Horn of Africa, Ethiopia is a home for millions children unvaccinated and thousands of under fife deaths that occur every year [9].  In the period from 2000 to 2019, Ethiopia has made some significant progress in the health status of children. This is reflected in various indicators including the U5MR fell from 166 to 55 deaths per 1000 live births—a 67

Socio demographic Characteristics of the Study Population 
Among the total study participants (399), 389 mothers/caretakers of children aged 12–23 months were interviewed (97.3 %). The median age of the respondents was 28 years, which ranges from 24 to 29 years. Most (87.9%) of the mothers/caretakers were followers of Orthodox Christian religion. Majority (91.3%) of the mothers/caretakers were married. From the total respondents, 196 (50.4%) of mothers/caretakers can read and write (Table1).

Socio demographic Characteristics of the Index Child 
A total of 389 children of aged 12–23 months/caretakers were included. The numbers of male and female participants were 184 (47.3%) and 205 (52.7%), respectively. The mean and median ages of children’s were 18 and 18.3 months, respectively. Majority (90%) of children were born at health institution, while 39 (10%) of them at home (Table 2). 

Maternal Health Care Utilization: Regarding ANC follow-up, majority (57.4%) of the mothers/caretakers had at least one antenatal care (ANC) follow-up during their pregnancy. The remaining 243(64.3%) had four visits and 109 (28.8%), and 27 (7.0%) of them had three and two visits, respectively.From the total respondents, 186 (49.2%) of them had postnatal care (PNC) follow-up.

Availability and Accessibility of Vaccination Service: More than half (56.2%) of mothers/caretakers responded that they could reach the vaccination site within 30 minutes on foot. All of the respondents were reported that they had access to the health facility that provides vaccination services. 

Knowledge of Mothers/Caretakers on Vaccine and Vaccine:  According to this study, all (100%) of mothers/ caretaker had heard about vaccination as a specificprogram. Major sources of information for it includes; television (51.9%), health workers (27.2%), friends (10.5%) and radio (8.5%). Majority (69.4%) of the participants knew that the objective of vaccinating children was to prevent disease, while 3(0.8%) of them said that they had no idea about the objectives of vaccination. Concerning the age at which vaccination begins, two hundred thirty five (60.4%) and one hundred thirty five (34.7%) of them reported that it should be started just after birth and after six weeks, respectively. But, sixteen (4.1%) of them reported that vaccination could be started at any time and three (0.8%) of them reported that they did not know. Also regarding the question of how many sessions needed to get full vaccination,  majority (74.6%) of them answered four sessions and 61 (15.7%) of them responded that less than four sessions are needed. Regarding the age at which children’s vaccination is completed, 320(82.3%) of them responded that it ends at nine months (Table 3)

Immunization coverage of Children Aged 12–23 Months  
In this study, 365 (93.8%) of mothers/caretakers showed the child vaccination card during the survey. According to a finding from card plus history, all of them have taken one or more of the recommended vaccines. Of total vaccinated child, 299(76.9%) of them had finished all the recommended doses and 90(23.1%) did not complete the entire doses.  
Out of the total surveyed children aged 12–23 months, vaccination card was only seen and confirmed for 365 (93.8%) children. From 365 vaccinated children by card only, 90.4% received OPV1, followed by OPV2 (89.6%) and BCG (88.2%). Penta 3 was taken by 88.5% and measles vaccine was taken by 86.1% and based on the available vaccination card, only287 (78.6%) children completed all the recommended vaccines. 
Based on the vaccination card and the mother’s/caretakers recall, from the total study participants, 299 (76.9%) were claimed full immunized while 90 (23.1%) were partially vaccinated. 
The respondents who were not completing their children’s vaccination were asked for reasons of failure. Accordingly, the majority (35.7%) of them replied that forgetting the appointment date was the root cause for not completing vaccination. Also 14.9% of them provided lack of vaccine on the day of appointment as a main reason for vaccine dropout. 
Concerning the reason for not ever vaccinating their child, the majority (41.3%) of them replied fear of the side effects of vaccination as a cause while 36.2%, 15.5%, and 6.9% of respondents replied that many injection at one visit, child sickness and lack of awareness are major causes for not ever vaccinating their child, respectively.
Factors Associated with Child Vaccination Status 
In the multivariate logistic regression analysis, the following four variables were identified as independently associated with postpartum modern contraceptive use. These were maternal educational status, ANC follow-up during pregnancy, place of index child delivery and maternal knowledge on vaccine and vaccine   preventable disease. 
Women who attended diploma level education were 1.2 times more likely to full vaccinate their children than those who are Illiterate (AOR=1.2, 95%CI (1.41-2.42)).  Women who gave birth at health institution were 3.28 times more likely to full vaccinate their children than those who deliver at home (AOR=3.28, 95%CI (1.38-3.67)). The odds of full vaccinating children was 5 times higher among women who attend ANC service compared to those who did not (AOR=5.04, 95%CI (1.35-12.06). Women who had knowledge on vaccine and vaccine  preventable disease were 4.12 times more likely to full vaccinate their children than those who didn’t (AOR=4.12, 95%CI (3.0-10.6)) (Table 4). 

This study tried to assess immunization coverage and maternal factors associated with it among children aged 12 to 23 months in Debre markos town. Based on the finding of this study, out of total children surveyed by card plus history, the coverage of full immunization observed was 299 (76.9%). This figure was relatively higher compared with different studies conducted in various regions including North Eastern India [28] and Uganda [29] where the proportion of full immunized children aged 12–23 months was 62.2% and 52%, respectively. It was also much higher than a survey done in Oromia regional state where immunization coverage was 35.4% [30]. These differences may be attributed to maternal satisfaction about vaccination that helps to complete the schedule which depends mainly on maternal knowledge about vaccination. Another way used to get information about vaccination status of children in this method was asking mothers to show infant vaccination card. 
According to the findings obtained from this study, maternal education had significant association with full vaccination coverage. This may be explained as increasing in educational level helps a woman to have better awareness on vaccine and vaccine-preventable diseases so that they can make decision to vaccinate their children for all schedules. In addition, it is a fact that as educational status of a woman increased, health seeking behavior could be increased which might lead them to vaccinate their children. Studies elsewhere have revealed a similar pattern of relationship between educational level and full immunization coverage [15, 16]. This study had revealed that place of delivery of the index child showed a significant association; with full vaccination coverage. This finding was coherent with a result obtained from Kenya where being born in hospital increased the probability of the child being immunized [31]. This is likely because if delivery occurs in health care facility, some vaccines such as BCG is normally administered which increases the likelihood of the child being immunized which in turn amplifies the vaccination coverage. Additionally mother who delivers in a hospital is more likely to receive training on benefits of vaccination from health service providers. 
The result of this study showed that receiving antenatal care visit was an important determinant factor for full vaccination status. This finding is consistent with that of a finding obtained from Kenya [31] and Ambo district [30]. This could have happened due to mother’s health seeking behavior and mothers may discuss with health professional about vaccine and vaccine preventable diseases, importance of vaccination, time of vaccine initiation and when vaccine is completed, and possible side effects associated with a vaccine. 
Furthermore, knowledge of mothers on vaccination and vaccine preventable disease showed a significant association with full vaccination of children. This might be explained in that knowledge acquired can change mothers’ health seeking behavior as well as they can understand as there is no best way to fight such disease except vaccination services. A study conducted in in Oromia region Ambo district [30] and Jijiga [16] supports this finding. In this study, forgetting the appointment date was mentioned as the commonest reason for not completing vaccination while fear of the side effects of vaccination was cited as a common reason for never vaccinating their child at all. This finding was supported with a finding obtained from Nigeria [32].
Conclusion 
The finding from this study revealed that child immunization coverage in the studied area was low. Educational level of the mother, knowledge on vaccine and vaccine-preventable disease, antenatal care follow-up and place of delivery of the index child were statistically significant maternal factors of full immunization coverage of children. The main reasons described for not completing vaccination by respondents was forgetting the appointment date. In addition, the common reason for never vaccinating their child was fear of vaccine side effects. Therefore, health extension workers should work on improvements in women’s educational status, encourage mothers to have ANC follow-up and institutional delivery and they should discuss vaccination with mothers in order to improve their knowledge on vaccine preventable disease and the advantage of complete vaccination services.