Study design and setting
A community-based unmatched case-control study was conducted from February to March 2018 in Semen Bench district, Bench Majii Zone, South west Ethiopia. The district is known for frequent outbreaks of vaccine-preventable diseases, especially measles. It has 31 kebeles and an estimated total population of 138,556. The study was conducted in seven kebeles (the smallest administrative units in Ethiopia
Source population
All household with mothers/care givers who had children in the age group 12-23 months of age residing in semen Bench district for both cases and controls.
Study population
Study population for cases: Selected eligible households with mothers/care givers who had children in the age group of 12 to 23 months who did not complete the recommended vaccination.
Study population for controls: Selected eligible households with mothers/care givers who had children in the age group of 12 to 23 months who completed the recommended vaccination.
Sample Size Determination
Sample size was determined by using Stat Calc program of the Epi Info version 7; Used to calculate the sample size with exposure among controls is 84.4% from previous study in Tigray region (18) , and 5% marginal error, 95% confidence interval, power of 80%, case to control ratio of 1:2 and 10% of non-response rate was considered. Calculated sample size in all Independent (exposure) variables are considered and place of residence is chosen as an independent variable since it gave maximum sample size as compared to other exposure variables. The larger sample size was 282+30 (10% non-response rate) =312 (104 cases and 208 controls)
Sampling Technique and Procedures
Simple Random sampling technique was used to reach household level. The seven districts were selected by simple random sampling (lottery method). And the calculated sample size was allocated proportionally according to their population. From the two years family folder list of cases and controls were selected then by Computer Generated Simple Random Sampling Techniques the required number of cases and controls were selected. From Serty distract 38 sample case 13 control 25: Muya distract 47 sample case 16 control 31 :Yikir Demoze distract 58 sample case 19 control 39: Kasha distract 50 sample case 17 control 33: Boseka distract 30 sample case 10 control 20: Endekal distract 53 sample case 17 control 36: Genga distract 36 sample case 12 control 24
Operational Definition
Complete (full) vaccination: The childhood vaccination status once a child has received all recommended vaccines, including BCG, three doses of pentavalent, three doses of PCV, two doses of Rota vaccine, three doses of polio and measles vaccines by the age of 12 months(18).
Incomplete (partial) vaccination/Defaulter: The childhood vaccination status if the child missed at least one of the recommended vaccines (the recommended vaccines include BCG, three doses of pentavalent, three doses of PCV, two doses of Rota vaccine, three doses of polio and measles vaccines by the age of 12 months) (18).
Poor knowledge: Those mothers /respondents who scored below mean score of the knowledge questions.
Good knowledge: Those mothers /respondents who scored equal and above mean score of the knowledge questions.
Data collection tool and quality control
The data were collected using a structured questionnaire adapted from a previous study [4-12]. Before undertaking data collection, the questionnaire was pretested on other similar population taking 5 % of the total sample outside the study area and necessary modifications were made. The questionnaire was prepared originally in English and translated to the local language. The questionnaire was further translated from local language to English to check for consistency. The primary respondent was the mother of the child. In case of her absence, the questionnaire could also be completed by the father or another adult in the household acting as the primary caregiver. The data were collected by trained, diploma midwife, fluent in local language, using the structured questionnaire translated to local language. Three health professionals with bachelor’s degree in health supervised the data collection process. Before data collection, the data collectors and supervisors were recruited and training was given on the objective of the study and techniques of data collection for two days
Data Processing and Analysis
Data were entered using EPI- Info version 7 and analyzed using SPSS-version 21 statistical software. Descriptive statistics were used to summarize the data, and a bivariable analysis was carried out to describe associations between exposure variables and childhood immunization status and assessed by chi-square and odds ratio with a significance level of p-value ≤ 0.05. Variables with p-value ≤ 0.25 were included in the final model. In the multivariable analysis, additionally model fitness was checked by Hosmer and Lemeshow goodness of test and p-value ≤ 0.05 was applied to identify independent factors of incomplete childhood immunization.