Introduction

“All individuals and communities have to enjoy lives free from vaccine-preventable diseases”1. Every year vaccination saves millions of lives2. It is a fruitful, cost-effective health intervention, and with proven strategies that make it accessible to even the most hard-to-reach and vulnerable populations1,2.

Globally, vaccination prevents 2–3 million deaths each year2. In 2018, worldwide vaccination coverage for three doses of the Pentavalent vaccine was 86%1. In Africa vaccination coverage was 76% in 20153.

According to the Ethiopian Minister of Health EPI (Expanded Program Immunization) guideline, all basic vaccination coverage is having vaccinated BCG (bacillus Calmette-Guérin), Pentavalent, Polio, and Measles. In Ethiopia four out of every ten children had received basic vaccination. Based on the mini Ethiopian Demographic Health Survey (EDHS) 2019, the basic vaccination coverage had reached 43%4.

Around 19.4 million infants have not received basic vaccination Worldwide2. One in five children had not had access to vaccination in Africa5. Ethiopia is one of the top ten countries carrying the 60% world burden of unvaccinated infants2.

Vaccine-preventable diseases have been reduced drastically due to the implementation of vaccination programs in Africa5. However, vaccination coverage still has not reached the target yet. This is due to many different factors such as low health education, limited access to healthcare, and inequity in access to immunization services3,6.

In Ethiopia also, different studies showed that vaccination coverage is affected by different factors. Based on those studies, antenatal care (ANC) visits, women’s decision-making autonomy, the number of under-five children in the household, the mother’s education, and proximity to the health facility, and residence were increasingly associated with the completion of vaccination7,8,9,10.

Regarding those different studies done in Ethiopia, maternal education was the most commonly mentioned factor4,8, 11,12,13. However, there was inconsistency, and didn’t confirm whether it was a factor or not. Needs systematic review and meta-analysis for the confirmation of the association between maternal education and complete childhood vaccination must be conducted. This systematic review and meta-analysis aimed to examine the association between maternal education and completion of childhood vaccination among aged 12–23 months children in Ethiopia. The findings of this study will help policymakers, programmers, researchers, and other stakeholders to be certain and take a lesson on the issue.

Methods

This study was carried out in strict compliance with systematic review and Meta-analysis with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analysis) guidelines14.

Patient and public involvement

No patients or the public were involved in this review.

Search strategy

Using relevant Medical Subject Headings (MeSH) terms, a final search strategy was developed. Searches were conducted on 05 February 2020 on PubMed-Medline, EMBASE, SCOPUS, Global Health, and Google Scholar for articles published from January 2010 to January 2020 using different searching terms as shown in Table 1. Unpublished papers are also searched from different online sites such as Google. We considered reviewing articles with full PDF texts of relevant studies accessed. We also tried to contact the authors of relevant studies for missing information (Tables 1 and 2).

Table 1 Search terms.
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Table 2 Population, exposure, comparator, and outcome for the systematic review.
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Selection criteria

We considered our review of all quantitative observational studies (cross-sectional, case-control, and cohort studies). The authors (Aregawi and Kisanet) screened all the titles and abstracts identified through database searches. We excluded all papers that did not fulfill the inclusion criteria. Disagreements were resolved using discussion and consensus. Papers with full text were then retrieved. We used PRISMA (preferred reporting items for systematic reviews and meta-analysis) guidelines14. Studies were eligible if: they were conducted in Ethiopia and included maternal education as a determinant of the childhood vaccination coverage in children aged 12–23 months, had full text, published from January 2010 to January 2020, written in English, and done with observational study designs. A study was excluded if: not have parameters, studies with the specific vaccines, and vaccines out of childhood vaccination.

Quality criteria

Based on the Ethiopian Minister of Health, complete vaccination means if the child took 1 dose of BCG, 3 doses of polio, 3 doses of pentavalent, 3 doses of PCV, and 1 dose of measles. We did a critical appraisal for all eligible studies to include in the meta-analysis.

Data extraction

Data were extracted from the eligible articles based on their study characteristics; including publication information (author and year of publication), study region, setting, design, period, sample size, children’s age, maternal education parameter, and vaccine types. The number of children per maternal education level, the number of children fully vaccinated per maternal education level, and the percentage of children fully vaccinated per maternal education level were extracted for data analysis. Data were sorted into the nine regional states and 2 self-administrative cities.

Risk of bias

Papers were assessed for quality and risk of bias using an adapted version of the certified “Quality Assessment Tool for Quantitative Studies” by the Effective Public Health Practice Project15,16,17. Each study was also assessed and done critical appraisal using the checklist “The Joanna Briggs Institute Critical Appraisal tools for use in JBI Systematic Reviews” according to the criteria for inclusion, describing study subjects and study setting, measuring exposure validly and reliably, identifying of confounding factor, utilizing standard criteria to measure the objective, strategies to deal with confounding, measuring outcome validly and reliably, and using appropriate statistical analysis. The articles were rated its quality as “strong”, “moderate” or “weak”18,19.

Summary measures and synthesis of results

For the meta-analysis, the independent variable maternal education variable was categorized under three categories classified as “Have no formal education/illiterate”, “primary education” and “secondary and/or higher education”. We excluded papers from the meta-analysis if they had only two categories of maternal education level (“educated and non-educated” or “illiterate and literate”), had no clear categories, and had no values for their categories.

A pooled odds ratio was determined using an Influential analysis (Fixed effect model) and random-effects model using the classified categories from each included paper20,21 as large heterogeneity was anticipated considering the differences in study characteristics, such as varied sample size, region, and settings. The analysis was performed in the R statistical software R Studio version 3.622.

Sub-category analysis was also conducted for each region of the country. The reason why we used the years between 2010 and 2020 was, that the Ethiopian Health Sector Transformation Plan introduced new policy Phase-I in 2010–2015 and phase-II from 2015 to 202023.

Forest plots were created for the “primary education” and “secondary and/or higher education” separately taking “have no education/illiterate” as a reference for both categories. And also determined the individual study odds ratios and 95% Confidence Intervals, pooled estimate, and the I2-value for testing the heterogeneity24,25.

Publication bias

Graphically using funnel plots and statistically egger tests were also conducted for both categories independently using R studio statistical software 3.6 version to assess for publication bias of the included papers26,27.

Results

Study selection

Out of 16,273 papers, 43 studies met the eligibility criteria for the qualitative synthesis of this systematic review, and 28 articles fulfilled the criteria for quantitative synthesis of meta-analysis (Fig. 1).

Figure 1
figure 1

Flow diagram of study selection.

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The main eligibility criteria for excluding the 841 papers were that they were conducted outside of Ethiopia and were irrelevant to the topic. We excluded the maternal education variable, which was classified into three categories: “illiterate/literate,” “educated/not-educated,” and “no education and primary/secondary and above,” or “primary/secondary.” Articles that had three classifications for maternal education (No education, primary education, and secondary and above) were included in the meta-analysis synthesis.

Study range and characteristics

The authors independently assessed the quality of the articles using the global score critical appraisal checklist. Twenty-one articles were rated as moderate quality, seven articles were rated as strong quality, and fifteen articles were rated as weak quality. Articles with weak quality scores were excluded from the meta-analysis (Table 3).

Table 3 List of studies included in qualitative synthesis to show the effect of maternal education on completion of childhood vaccination in Ethiopia.
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Among the twenty-eight articles included in the meta-analysis, the total number of children was 32,361. The sample size ranged from 248 to 8905 children, with a mean ± SD of 8905 ± 1781. (Table 4) In this study, 6503 mothers (31.4%) who had no educational status fully vaccinated their children. Among mothers with primary education, 3698 (49.6%) fully vaccinated their children. Mothers with a secondary and above level of education had fully vaccinated 2675 children (69%) (Table 4).

Table 4 List of studies included in the meta-analysis to show the effect of maternal education on the completion of childhood vaccination in Ethiopia.
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Data extraction and meta-analysis

The meta-analysis was conducted separately for both “primary education” and “secondary and above level of education,” with “no education” as the reference. We performed forest plots and funnel plots for both models using R-studio statistical software.

The meta-analysis revealed that children whose mothers had primary education had 1.866 times higher odds (95% CI 1.76–1.98) of receiving full childhood vaccination compared to those whose mothers had no education. Although the effect (OR) of 4 studies showed a negative association with completing vaccination (less than 1), the effect of the remaining 24 studies resulted in an OR greater than 1 (positive effect of having primary education). This resulted in a range of effects from 0.35 (0.18–0.68) to 23.19 (15.17–35.43). The effect size varied significantly among studies, with an overall I-squared value of 89.5% (p < 0.001), indicating a high level of heterogeneity among the studies (Fig. 8).

Secondly, the odds of full childhood vaccination were 3.47 times (95% CI 3.18–3.78) higher in children whose mothers had secondary education and above, compared to those whose mothers had no education. Although the effect (OR) of 4 studies showed a negative association with completing vaccination (less than 1), the effect of the remaining 24 studies resulted in an OR greater than 1 (positive effect of having primary education). This resulted in a range of effects from 0.35 (0.07–0.1.67) to 11.29 (4.73–26.9). The effect size varied significantly between studies, with an overall I-squared value of 89.8% (p < 0.001). This also indicates a high level of heterogeneity among the studies (Fig. 9).

In addition to this, the l’abbe plot showed that most of the studies were located at the top right and above the line, indicating a positive effect of maternal education on completing childhood vaccination (Figs. 9 and 10). We also conducted a funnel plot to observe publication bias, which revealed slight asymmetry among the studies. This bias may be attributed to variations in sample size. It reports Egger’s test for the primary school, t = − 0.61, df = 26, p-value = 0.5468, bias estimate: − 0.9537, SE = 1.5620; where as for the secondary school and above, t = − 1.38, df = 26, p-value = 0.0948, bias estimate: − 1.1428, and SE = 1.6395 (Fig. 9).

Sub-group analysis in regions

In the subgroup analysis, we only conducted for three regions: Oromia, Amhara, and South Ethiopia. The subgroup analysis of these regions revealed that the overall effect size was highest in the Oromia region. In this region, the odds of full childhood vaccination were 2.06 times (95% CI 1.71–2.49) higher if the mother had primary education compared to mothers with no education (Fig. 2). Additionally, the odds of full childhood vaccination were 2.84 times (95% CI 2.1–2.3.84) higher if the mother had secondary education compared to mothers with no education (Fig. 3). All studies within the Oromia region subgroup were significant, although the funnel plot indicated some slight asymmetry among the studies (Fig. 2).

Figure 2
figure 2

Forest plot of the effect of primary and secondary and above maternal education on full child vaccination in the Oromia region respectively.

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Figure 3
figure 3

Funnel plot of the effect of primary and secondary and above maternal education on full child vaccination in the Oromia region respectively.

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The overall effect for the south region was an increased odds of 1.41 (95% CI 1.2–1.65) for completion of childhood vaccination with primary education, and an increased odds of 2.3 (95% CI 1.79–2.96) for completion of childhood vaccination with secondary and above maternal education. There were three statistically insignificant studies in the South Ethiopia subgroup. The funnel plot indicated the presence of publication bias (Figs. 4 and 5).

Figure 4
figure 4

Forest plot of the effect of primary and secondary and above maternal education on full child vaccination in the South Ethiopia region.

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Figure 5
figure 5

Forest plot of the effect of primary and secondary and above maternal education on full child vaccination in the South Ethiopia region.

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In the Amhara region subgroup, the association between having primary education and completing child vaccination yielded statistically insignificant results and showed low heterogeneity, with odds of 1.56 (95% CI 1.25–1.95) and a heterogeneity test I2 of 45% (Fig. 6). The overall effect for the Amhara region indicated an increased odds ratio of 1.52 (95% CI 1.25–1.86) for the completion of childhood vaccination when mothers had secondary education or above (Fig. 7). Within this subgroup, two studies were statistically insignificant about maternal education at the secondary level and above and its impact on full child vaccination (Figs. 6 and 7).

Figure 6
figure 6

Forest plot of the effect of primary and secondary and above maternal education on full child vaccination in the Amhara region.

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Figure 7
figure 7

Forest plot of the effect of primary and secondary and above maternal education on full child vaccination in the Amhara region.

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Discussion

The study aimed to examine the association between maternal education and completion of childhood vaccination among aged 12–23 months children in Ethiopia. Based on this systematic review and meta-analysis, the overall pooled effect indicates a positive association between maternal education and the completion of childhood vaccination. The primary finding of this meta-analysis is that having primary school maternal education is correlated with a 1.87 times higher likelihood (95% CI 1.76–1.98) of completing childhood vaccination compared to having no education. Additionally, the pooled effect of having a secondary and above level of education is 3.47 times higher (95% CI 3.18–3.78) than having no education. These findings suggest that as maternal education status increases, the likelihood of their children being fully vaccinated also increases. The systematic review also reveals that the percentage of children who are fully vaccinated increases progressively as the maternal education level goes from “no education” to “primary education” to “secondary and above level of education.” This highlights the importance of maternal education in ensuring the completion of childhood vaccination. Educated mothers are more likely to be aware of vaccine-preventable diseases, understand the benefits of vaccination, and ensure the timely completion of vaccinations for their children. Literature from different regions and periods also supports these assumptions50,51,52,53,54. Conversely, mothers with no education may have poor knowledge about their child’s vaccination, childcare, and overall health. Maternal education plays a crucial role in fostering a positive attitude and perception towards child health12,55,56,57,58.

The meta-analysis also examines the effect of maternal education on completing childhood vaccination across different regions of the country through subgroup analysis. While a positive association is observed in the Oromia, Amhara, and South Ethiopia regions, the strength of the effect varies across these regions. This variation may be attributed to factors such as sample size, maternal age, household income, location, accessibility to education, distance to health facilities, living standards, and other unestimated factors.

Strengths and limitations of the study

This systematic review and meta-analysis confirmed that there is a positive association between maternal education and completion of childhood vaccination in Ethiopia using R-studio statistical software.

However, this study used studies written in English only and this could potentially lead to language bias. We also included studies that had a free full PDF only, and this might have some limitations in generalization even though the authors were contacted for the raw data. We also didn’t make subgroup analyses using study year, sample size, and other variables; this is because of the problem related to the distribution of the studies with those variables (Figs. 8, 9, 10).

Figure 8
figure 8

Forest plot of the effect of primary compared to secondary and above maternal education on full child vaccination in Ethiopia.

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Figure 9
figure 9

Funnel plot of the effect of primary and secondary and above maternal education on full child vaccination in Ethiopia.

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Figure 10
figure 10

Publication bias of the effect of primary and secondary and above maternal education on full child vaccination in Ethiopia.

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Conclusion

This systematic review and meta-analysis study revealed that as the maternal level of education increases the completeness of childhood vaccination accelerates. And then, investment in maternal education should be the prioritized intervention because it empowers the mother and this will help in reducing and preventing the vaccine-preventable diseases and associated risks.