Introduction

Vaccination has long been recognized as one of the most effective ways to reduce child mortality [1]. It has played a significant role, particularly for children, and is considered a major achievement and relevant in preventing childhood diseases worldwide. In practice, the terms “vaccination” and “immunization” are interchangeable [2]. Improving access to immunization is critical to meeting the Sustainable Development Goals (SDGs). Childhood vaccination is highly effective in preventing vaccine-preventable diseases [1]. The discovery and introduction of the smallpox vaccine have greatly reduced disease prevalence worldwide, with 29 vaccine-preventable illnesses recommended by the World Health Organization (WHO) [3]. Despite the numerous ways to reduce the number of children dying from vaccine-preventable diseases, immunizations have improved immunity in 9 out of every 10 children [2]. Vaccines are very effective when major risk factors like malnutrition, air pollution and diarrheal diseases are eliminated, as well as treatment accessibility is improved.

Poor adherence to vaccination still remains a challenge in many regions across the world [4]. Globally, it is estimated that about 22.4 million children under one year of age were not vaccinated with the third dose of pentavalent vaccine (Diphtheria Pertussis-Tetanus-Hepatitis B-Haemophilus type b influenza vaccine (DPT-HB-Hib) [3]. One out of five African children is estimated to not receive all the necessary and basic vaccinations. Consequently, over 30 million African children under five still suffer from vaccine-preventable diseases (VPDs) every year. Approximately 58% of all deaths due to VPDs occur in children over half a million a year [5]. Several factors contribute to vaccines’ low coverage as highlighted in the literature. Households, lack of communication, and knowledge about immunization have been reported to be major contributors [6]. One of the major contributors to vaccine utilization in Africa highlighted is economic conditions, which affect the ability to afford and keep immunization record documents in good condition [7]. A study published in the literature looked into cultural perspectives as a contributor to low vaccination coverage. It was discovered to be linked with people’s misinformed perceptions of vaccines due to their cultural background [8]. In Pakistan, is linked to the father’s job as manual labour [9]. In addition, mothers’ perception of the severity of vaccine-preventable disease, as well as mothers’ beliefs do not influence the uptake as reported in a study conducted in Tanzania [10].

Sub-Saharan Africa is still dealing with a variety of program and policy challenges related to childhood immunization [11]. Numerous studies have been conducted to investigate factors associated with childhood immunization in Sub-Saharan Africa, some of which indicate parental attitudes, a lack of knowledge among health workers, and barriers that can be overcome by improving outreach services [12]. Furthermore, a study conducted in Burkina Faso discovered that education, both at the individual and community levels, is no longer associated with complete vaccination of children [13]. This demonstrates that there are differences in factors within the African region, such as the need for uptake. It has been observed that many countries in the sub-Saharan African region have proven to have a high vaccination coverage, but due to various limitations have not achieved this upscaled coverage, necessitating the need to study underlying factors [11].

Several West African immunization programs have made significant progress in increasing vaccination coverage, which is expected to have a significant impact on the reduction of vaccine-preventable diseases [1]. The Gambia, Sierra Leon, and Liberia for example, have shown that the immunization strategies are effective when there are good political and cultural will; however, vaccination programs should be constantly monitored and evaluated by the Ministries of Health. To raise societal awareness and vaccine acceptance, strong community-based health education efforts are desperately needed as part of initiatives to increase vaccine service utilization for these high-risk classes. This study examines the uptake and determinants of childhood vaccination status among children under the age of one, using the available DHS data for Gambia, Sierra Leon, and Liberia.

Methods

Data source

The 2019-20 Demographic and Health Survey (DHS) data from Gambia, Sierra Leone, and Liberia were pooled for the analysis. In the three countries, the DHS used a stratified two-stage cluster sampling approach to create a population-based sample. Following the probability proportional to the size of the Enumerated Areas (EAs), 281 (The Gambia), 325 (Liberia), and 578 (Sierra Leone) clusters/EAs were selected in the first stage of the survey. The second stage involved a methodical selection of 25 (The Gambia), 30 (Liberia), 24 (Sierra Leone) households from each cluster/EA and only 8,362 (The Gambia), 5, 704 (Liberia), 9,889 (Sierra Leone) women of reproductive age with children less than 60 months were interviewed successfully. In DHS, specific questions were asked to women about children’s health. Questions related to immunization coverage are of particular interest. We pooled the DHS survey data of the three countries, and a total weighted sample of 5,368 children aged 0–12 months was included in the study. In the three countries, through the USAID-funded MEASURE DHS programme, ICF International provided technical and financial assistance to the Ministry of Health in collaboration with the Bureau of Statistics of each country that implemented the survey.

Variable selection and measurement

Outcome variables. The study outcome variable was childhood vaccination status among children aged 0–12 months. This was classified into two categories: “Fully vaccinated” a child under 23 months who received WHO recommended vaccination against tuberculosis (also known as BCG), three doses of DPT-HepB-Hib (Penta), three doses of polio vaccines, and one dose of vaccination against measles; “Partially vaccinated” who missed at least one of any of the doses of the routine vaccines before turning 1 year or within 12–23 months old [14,15,16,17,18].

Explanatory variables. Thirteen independent variables were utilized in the study based on a thorough literature review and datasets availability [14,15,16]; the variables are listed in Table 1.

The WHO framework on epidemiology of the unimmunized child [19, 20] describes the different factors affecting child’s immunization into four main categories: health care immunization system, communication and information, family characteristics, and parental attitudes and knowledge [21]. In our study, the immunization system category included the distance to health facility, and the need to take transportation. The communication and information category included: use of mass media according to the levels of access and source (radio, TV and newspapers), family characteristics included the followings variables: mother’s and father’s education level, mother’s age at childbirth, marital status, household level of poverty assessed by the wealth quintile, ethnic group, religion, child gender, birth order, urban/rural residence (urban/rural), and region of residence. Variables on familiarity and use of other health care services such as antenatal care during pregnancy, postnatal care, and the relative distance to the closest health center represented the parental attitudes/knowledge. Finally, we included the gender relationship such as the involvement of women in household decision making.

Table 1 Definition of independent variables used in the analysis
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Statistical analysis

Stata survey (‘svy’) module was used to adjust for stratification, clustering and sampling weights provided in the dataset. The data was weighted (v005/1,000,000) throughout the analysis to ensure DHS sample representativeness and to obtain reliable estimates and standard errors before data analysis. Descriptive statistics were used to describe the level of immunization coverage by socio-demographic characteristics, the distributions were expressed as frequencies and percentages. Bivariate and multivariable logistic regression analyses were conducted to identify the determinants of full immunization. Bivariate analyses were used to examine the crude association between each independent variable and full vaccination. Multivariable logistic regression was used to examine the adjusted association between each independent variable and full childhood vaccination. Binary logistic regression was chosen because our dependent variable was dichotomous (i.e., 0 - partially vaccinated and 1- fully vaccinated). Variables in bivariate analysis with p-values less than 0.05 were entered into the multivariable analysis. Adjusted odds ratio (aOR) and 95% confidence Interval (CI) were used to assess the strength of associations between the outcome and the independent variables. The threshold for statistical significance was set at p < 0.05. We used the Bayesian Deviance Information Criterion (BIC) to assess the goodness of fit of the model. Variance Inflation Factor (VIF) was applied to test for multicollinearity. All the study data were analyzed using Stata version 17 and IBM SPSS version 25.

Ethical approval

The datasets used in this research were population-based datasets that are freely available in the public domain. For reasons of confidentiality, specific characteristics that could be used to identify participants in the study were excluded. As a secondary study, MEASURE DHS/ICF International granted the authors permission to use the datasets.

Results

Socio-demographic characteristics of infants’ mothers in Gambia, Liberia and Sierra Leone

Based on the result from the pooled data as shown in Table 2, a total of 5,368 children aged 0 and 12 months were pooled across the three West African countries for the study. Child characteristics showed that about half (52.1%) of the children in the study sample were males and 47.9% were females. The family/parental characteristics showed that the mean age of child’s mother and father (± SD) was 27 years (± 6.8) and 38 years (± 11.1) respectively, almost half of the mothers (44.7%) and 49.5% of the fathers had no formal education. 86.3% of the mothers had more than 4 ANC visit, 42.8% never attended PNC, 79.0% delivered in public hospitals and 53.8% of the fathers made decision on vaccination. Household characteristics showed that among the respondents, 50.3% lived in rural area, 22.9% were among the poorest wealth quintile and 61.5% practiced Islam. Communication and information characteristics showed that 92.9% never read newspaper, 38.7% sometimes listened to radio, and 42.9% sometimes watched TV.

Table 2 Characteristics of weighted sample population
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Table 3: Bivariate analysis of factors associated with childhood vaccination among infant aged 0–12 months.

Similar proportions of male (15.1%) and female children (15.0%) reportedly had full vaccination. Children whose mother were 25–34 years (16.3%) and 35 & above (14.4%) had higher proportion of full vaccination compared to those less than 24 years (13.9%) as shown in Table 3. Children whose mother had no education (14.4%) had lower full vaccination status compared to those with secondary (16.1%) and tertiary (16.1%) education. The proportion of full vaccination was higher among children who lived in urban area (15.8%) compared to those who resided in the rural area (14.3%). Higher proportion of full vaccination was recorded among children whose mothers were married (15.4%) compared to those single (13.8%) or widowed/divorced (12.3%). Higher proportion of full vaccination was recorded among those who sometimes watched TV (18.1%) or listened to radio (15.8%) or read newspaper (16.2%). The higher proportion of full vaccination was recorded among children whose mother had no ANC visit (19.6%) and had PNC visit (16.5%). Lower proportion of full vaccination status was recorded among those whose mothers delivered at home (12.8%) and had big problem about the distance to the health facility (12.8%). Bivariate analysis indicated that father’s education, religion, watching TV and listening to radio, ANC visit, PNC visit, distance to health facility were significant risk factors associated with full vaccination among children 0–12 months in three West African countries.

Table 3 Bivariate analysis of the association between the explanatory variables and childhood vaccination among children aged 0–12 months in three West African countries
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Determinants of childhood vaccination among infant aged 0–12 months in the three west african countries

Table 4 shows the binary logistic regression results on the factors associated with childhood full vaccination in three West African countries. In the adjusted model, children whose mother attended PNC visit had higher odds (aOR = 1.23, 95% CI = 1.03–1.46) of being fully vaccinated compared to those who had no visit. Religion was significantly associated with full vaccination. Children whose father had primary education had lower odds (aOR = 0.67, 95% CI = 0.48–0.96) of being fully vaccinated compared to those who had no education. Children whose household never watched TV had lower odds (aOR = 0.68, 95% CI = 0.56–0.82) of full vaccination compared to those who watched sometimes. Finally, also children whose mother attended one to three ANC visit had lower odds (aOR = 0.59, 95% CI = 0.45–0.79) of being fully vaccinated compared to those who had more than four visit.

Table 4 Binary logistic regression analysis of factors associated with childhood vaccination among Children 0–12 months
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Discussion

Immunization has been shown to have a significant impact on vaccine preventable diseases. Despite these success and progress, vaccinations uptake is currently faced with several challenges, such as unequal access, lack of resources and vaccine hesitancy [5, 22,23,24,25]. The study found that religion, fathers’ education, and PNC visits are all factors that hinder vaccination uptake in children under one year of age. These findings are similar to other studies that reported culture, religion and community belief systems that were reported as potential barriers or deterrents to vaccine uptake in Africa [22, 26,27,28]. The study also revealed that children’s vaccination uptake is influenced by the socioeconomic and residential status of their caregivers. Families with higher incomes who live in cities have a better chance of getting their children vaccinated than low-income families who live in rural areas. Similar studies supported the critical influence of family support systems toward improving vaccine coverages among infants in Sub-Saharan African countries [22, 23, 27].

The study found that mothers who visited postnatal care had a higher chance of having their children vaccinated as compared to mothers who had no previous PNC visits. This is consistent with a study conducted in Benin and the findings revealed that children whose mothers had no antenatal care visits had a lower likelihood of receiving full immunization than those whose mothers had 1–3 visits. This demonstrates that contact with health care workers and a better understanding of vaccinations are factors that influence a child being vaccinated. However, institutional mistrust especially across local health authorities within the bigger picture of health systems related factors toward child vaccination uptake has created barriers and unequal access to immunization services and coverages in Africa [22, 24]. Parents can play an important role in ensuring their children are vaccinated, as evidence on the many benefits of vaccinations abound. However, there are other issues relating with the parents that affect vaccine uptake. The study’s findings also revealed that religion played a significant role in children’s vaccination uptake. This is consistent with the study conducted in Nigeria, which shows that religious belief was associated with the non-uptake of vaccination for children by their caregivers[29]. However, this was not the case in Burkina Faso as religion was contributary to partial immunization [30]. Religious beliefs shape how people see the world and determine how they live in many African settings [22, 23]. However, we can argue that individual levels of belief differ across regions and within countries, and thus how people live and what is accepted may influence vaccination uptake [23].

Furthermore, education was identified as a determinant of childhood vaccination uptake in the three countries. The study revealed that fathers with at least a primary level of education have a higher likelihood of their child being vaccinated than those with no formal education. This corroborate findings from a study conducted by Anu Rammohan et al., which revealed that in the six countries studied, having a father with a secondary (high school) education or higher was statistically significant and positively correlated with the likelihood of a child receiving measles vaccination, even if the mother is illiterate[31]. The findings were consistent with the study conducted in southeast Ethiopia that revealed that paternal education was also found to be statistically associated with child immunization status in a cross-sectional study of 591 children aged 12–23 months. In the study, children of fathers with secondary or higher education levels were three times more likely to be fully vaccinated than children whose fathers had no formal education [32]. This could be attributed to cultural influences in various African settings. In many instances, the decision of the family solely depends on the man, reflecting the patriarchal nature of African societies [25, 33]. This is a system where the educational levels of men as heads of households/families continuous to be influenced by culture and tradition.

Awareness of the importance of vaccination, as well as dangers of not being vaccinated demonstrates evidence that may explain why parents who have access to information and watch TV are more likely to have their children fully vaccinated. This is because, they may obtain information from a health facility, the media, or other sources and is consistent with the Ghanaian study [34]. The study findings demonstrate how vaccination knowledge and understanding can significantly influence vaccination uptake among children in African settings. In Mali, studies show that a lack of information and inconvenience led to only partial immunization of children [35]. This means that healthcare workers play a significant role, as do awareness campaigns that could be launched to educate the public and encourage positive behaviour. Using pooled data, from the Gambia, it was found that male children were fully vaccinated more than female children. This significantly differ from results in Liberia and Sierra Leone, where no significant differences were recorded in child sex and vaccination status. Furthermore, the pooled data showed that, the age of parents was significantly higher in Libera when compared to Gambia and Sierra Leone.

The governments of these nations need to strengthen their commitment towards WHO’s 2030 immunization agenda, which envisions a world where everyone, everywhere, at any age, has access to vaccines for good health and well-being [36]. Thus, a value-based Global Immunization Strategy is clearly needed, with the aim of putting citizens/populace at the center [37, 38]. There is also a need to set priorities for action to be implemented in the three African countries studied, for designing of an all-inclusive, integrated, and culturally adaptive new immunization strategies to be implemented. Some unpublished grey literature from Gambia reported that community-based immunization defaulter tracing strategies that are tailored in context-specific local settings have the potential to improve clinic attendance for childhood vaccination. These could also have the potential to influence political decisions that prioritizes immunization programs and strategies for local populace.

Study limitations

Since this survey was cross-sectional, causal relationships between variables of interest could not be definitively determined. There might be some level of recall bias in the study and non-response could also influence the accuracy of the data.

Conclusion

The prevalence of childhood vaccination uptake was low among children under 12 months of age and associated factors were number of mothers’ PNC visits, fathers’ educational level, access to watch TV as well as mothers’ number of ANC visits. There is a need to promote the uptake of childhood vaccination uptake across these three countries, especially among rural dwellers. Government should design robust, community-based social and behavioral change communication strategies and programs with strong elements of awareness raising at household and community levels.