Introduction

Despite some differences across countries, a child receives; one dose of the Bacille Calmette-Guérin (BCG) vaccine, three doses of the pentavalent vaccine, one dose of measles-containing vaccine (MCV), three doses of the oral polio vaccine (OPV), and three doses of the pneumococcal conjugate vaccine to be declared as fully vaccinated. Mali [1], Bangladesh [2], and South Africa [3] follow the same standard of child vaccination. Although there is a lot of success in eliminating vaccine-preventable diseases in developed countries, children in low-income countries are not still obtaining sufficient services because of the limited health system capacity, problems with the acceptability of the vaccine, and economic barriers to the service as a few reasons among all [4–7].

The complete or partial lack of those vaccines, mostly in low and middle-income countries, contributes to around three million preventable child losses each year [8, 9]. This full vaccination for children could not be achieved in most countries of the world [10]. To make changes in this regards the World Health Organization (WHO) launched the Expanded Immunization Program (EPI) in 1974 [11] Since its introduction the EPI has increased the global uptake for the four core vaccination (BCG, DPT, OPV, and MCV) from 5% in 1973 to over 80% in 2009 [12, 13]. Afterward, in 2012 the World Health Assembly of 194 member states endorsed the Global Vaccine Action Plan (GVAP) intending to put a framework to prevent millions of deaths by 2020 through equitable access to vaccines across the world [14].

The GVAP was a step toward universal health coverage (UHC) [15]. The World Health Organization (WHO) defines UHC as “all people have access to the health services they need, when and where they need them, without financial hardship. It includes the full range of essential health services, from health promotion to prevention, treatment, rehabilitation, and palliative care” [16]. Equity is an inherent dimension, which helps to systematically follow the status of UHC of different health service interventions. Despite these facts, full child vaccination has continued to be pro-rich in many low-income countries [17–19].

Previous studies in this area depict a social gradient in utilizing full child vaccination within a country [20–22]. In most cases, economically better-off countries are better in their health systems to give better health access to their citizens. Many low-income countries, on the other hand, are short of many aspects to fulfill the health service needs of the people [23, 24]. On the contrary, there is evidence indicating that poor people in economically good countries are still falling behind [25, 26]. As per our best search, how far the economically well countries went to fill the service gap between the poor, and rich within the country and how they are different from low-income countries is not well studied.

Besides, variables deemed important to assess the social determinants of health according to the WHO-commissioned social determinants of health inequality framework, [27] were examined in this study. The framework illustrates that socioeconomic stratifications like income, education, occupation, gender, and race/ethnicity determine people’s place in a social hierarchy (intermediary variables) like living/working conditions, behavioral, and psychological factors; which finally leads to differences in experiencing exposure and vulnerability to health-compromising conditions [27].

In general, theorists frame inequity in health as unavoidable versus avoidable; individual versus group; absolute versus relative, and so on [28]. Given it is a global concern, investigating both within and between country inequity assists global and local researchers and decision-makers to identify gaps and learn from experiences. Therefore, in this study, we presented the full child vaccination coverage, within and across countries wealth-based inequalities, and the possible predictors of inequalities by randomly selecting three countries (Mali, Bangladesh, and South Africa) from low-income (LI), lower-middle-income (LMI) and upper-middle-income (UMI) countries.

Materials and methods

Results

Socio-demographic characteristics

About 5801, 5128, and 1881 respondents from Mali, Bangladesh, and South Africa were included in the analysis. In all of the countries, the full vaccination was distributed proportionally to male and female children. In Mali and South Africa, the highest proportion of vaccinated children were from mothers between the age group of 25 and 29 years. In Bangladesh on the other hand, the highest proportion of 1137 [35.7%] respondents were younger mothers between 20 and 24 years. Almost all 1701 [97.3], and 3,147 [98.7] women in Mali and Bangladesh respectively were married. However, the highest proportion of 486 [55.1%] in South Africa were single mothers. The majority 1199 [68.6%] of the mothers of vaccinated children in Mali were not educated. Whereas, the highest proportion in Bangladesh 1583 [49.7], and South Africa 719 [81.5] have completed secondary education. Regarding residence, about three-quarters of mothers with fully vaccinated children in Mali and Bangladesh live in rural areas. In South Africa, the majority were residents of an urban setting [Table 1].

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Table 1. Socio-demographic characteristics of mothers and children with full vaccination status for Mali, Bangladesh, and South Africa.

https://doi.org/10.1371/journal.pone.0293522.t001

Vaccination status

Among the vaccines, the highest proportion of children was vaccinated with BCG in all three countries. On the contrary, the lowest proportion of children (46.1%) was vaccinated with three doses of Oral Polio Vaccine in Mali, (65.3%) were vaccinated with one dose of Measles Containing Vaccine in Bangladesh, and (49.9%) were vaccinated with three doses of Pneumococcal conjugate vaccine in South Africa. Overall, 30.2%, 62.9%, and 46.9% of children were fully vaccinated in Mali, Bangladesh, and South Africa respectively [Fig 1].

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Fig 1. The percentage of vaccinated children in Mali, Bangladesh, and South Africa in 2018, 2017, and 2016 respectively.

https://doi.org/10.1371/journal.pone.0293522.g001

Wealth-based inequity in full-vaccination

The concentration curve and index values revealed that in Mali there is a significant disparity in the full vaccination status of children between the lowest and highest wealth households [CInd: 0.05, 95% CI: 0.01, 0.09]. When we compare the lowest wealth, 20%, and the highest 20% in Mali, there is almost a 40% difference in favor of the highest-wealth households. The effect of wealth difference in full vaccination in Bangladesh favors the better-off family. However, in South Africa, full vaccination favors the poor even if the effect is not significant [Fig 2]. The sub-group analysis revealed the equity gap to be severe in rural settings compared to the urban in Mali. Children from wealthy families in rural areas benefit more than the poor. On the contrary, the rural settings children from poor families benefit more in South Africa. [Fig 3]

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Fig 2. Concentration curve indicating equity differences in full child vaccination in Mali (2018), Bangladesh (2017), and South Africa (2016).

https://doi.org/10.1371/journal.pone.0293522.g002

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Fig 3. Concentration index of equity differences stratified by place of residence (urban-rural) in child vaccination in Mali (2018), Bangladesh (2017), and South Africa (2016).

https://doi.org/10.1371/journal.pone.0293522.g003

The effect of wealth differences on full-child vaccination

Our multilevel poison regression model revealed several predictors of full-child vaccination. Considering other variables constant, the age of the mother was a positive factor affecting full child vaccination in all countries. Similarly, having an occupation was a positive driver in Mali, and Bangladesh while it negatively affected women in South Africa. Additionally, the frequency of watching television was the other positive factor. On the other side, the number of children in the house; richer, and poorest compared to the richest household was negatively associated with full child vaccination [Table 2].

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Table 2. The relationship between full child vaccination and equity parameters in Mali, Bangladesh, and South Africa.

https://doi.org/10.1371/journal.pone.0293522.t002

Discussion

For several years, eliminating the socio-economic-driven unnecessary gaps in health and health services use has been the target of various international goals including the Sustainable Development Goals (SDGs) [37]. Despite this, health service use is reported to be pro-rich in many low and middle-income countries [38]. Therefore, this study presented the experience of full child vaccination coverage, within and across country wealth-based inequalities, and predictors by taking Mali, Bangladesh, and South Africa.

The full child vaccination coverage was relatively better (62.9%) in Bangladesh, a LMI country. The result of good child vaccination coverage in Bangladesh might be attributed to the government’s initiative to implement a countrywide vaccine campaign like the Measles-rubella campaign in 2014. This increased the vaccination coverage by more than 75% and was certified by WHO as a polio-free country in 2014 [39]. Moreover, Bangladesh’s history in child vaccination coverage from the lowest base was exemplary for its contribution to the high reduction of childhood morbidity and mortality and received two GAVI best performance awards in 2009 and 2012 [40].

In our study, the full vaccination coverage in South Africa (46.9%) was lower than in Bangladesh but higher than in Mali (30.2%). In South Africa, while vaccine-preventable diseases are still a threat, a report in 2016 revealed that full child vaccination is deteriorating due to incomplete data, delayed national EPI surveys, inaccurate stock control, and poor cold-chain management [41]. On the other side, though Mali set priority agendas to increase full child vaccination by creating community health centers and responsible health committees in 2003; and deploying community health workers in 2011 [42, 43], our findings revealed that; Mali, has the least vaccination coverage.

The other finding in our study revealed that wealth-based Inequality favoring the better-off families was higher in Mali, followed by Bangladesh. In Mali, a 40% difference was observed, whereas it was 22% in Bangladesh. This result is commensurate with the findings of a study in other low-income countries [8, 44, 45]. This indicates that the healthcare system in many low-income countries is sub-optimal to reach the poor segment of the population. Even if promising progress regarding universal access to care has been documented in different low and middle-income countries like Burkina Faso, Botswana, and India [45, 46] the wealth-based inequality in Mali, Bangladesh, and other similar countries poses a great burden towards the global target of ending preventable child mortality by 2030 [47].

We can see the reasons both from the users’ and service providers’ perspectives. From the user’s viewpoint, access to education, access to the media, transportation access, and other many important aspects are low which, affects citizens of the country, especially the poor to use health services [48, 49]. From the service providers’ perspective, the low coverage of infrastructure tackles the health system to address people living in remote and slum areas [50]. Disproportionate allocation of the national budget for health services in many low-income countries restrains the health system from reaching those hard to reach economically poor proportion of society [51].

This multilevel poison regression also revealed that the richest proportion of the community in Mali experienced a better vaccination status. Compared to the richest, children from the richer and poorest families were 26% and 30% less likely to have a full vaccination. The finding is consistent with a finding in Ethiopia, one of the low-income countries, it shows children from a better-off family have a higher likelihood of being fully vaccinated [52]. Another study also shows that children in Mali were vulnerable to vaccine-preventable diseases [53]. The low vaccine coverage in most low-income countries coupled with high socio-economic disparity in full vaccination status contributes to lower achievements in child health indicators.

The other variable identified was the age of the mother. It was a significant positive driver for child vaccination in all countries included in the study. As age increases by one, the odds of vaccinating the child increase by 2–3%. This finding is similar to a study conducted in Afghanistan, a low-income country, which shows the lower the maternal age the lower the probability of child vaccination [54]. The possible reason might be that; women tend to gain lived experience about the importance of child vaccination either from themselves/ relatives or other neighbors through the years [55].

Maternal occupation was the other variable identified in this study. In Mali, and Bangladesh women having an occupation were 19% and 13% more likely to vaccinate their children respectively. Whereas in South Africa, those having an occupation were 24% less likely to vaccinate their child. The higher odds of child vaccination in women having an occupation are supported in different studies conducted in LMIC [56, 57]. It is well established that besides being employed gives financial stability to cover the transportation and related costs of child vaccination, it provides better autonomy and decision-making power for a woman [58].

The other variable identified was the number of children in the household. Both in Mali and Bangladesh, as the number of the child increased the probability of vaccinating their child went low by 5, and 7% respectively. This study is commensurate with a finding from a study done in Zimbabwe [59]. This may be explained as coupled with other burdens in the household; higher family size might create difficulties to afford expenditures associated with vaccination. The last variable identified was the frequency of watching television. The odds of child vaccination increased by 19–21% for those watching television at least once or above a week. This finding is supported by different studies in low-income countries [60, 61]. As exposure to mass media is found to be a crucial positive driver to increase child vaccination, intervention shall target to increase the information dissemination to favorably impact mothers’ choices.

Conclusion

In this study, compared to Mali and South Africa the vaccination coverage was higher in Bangladesh. Besides this, the vaccination service was far from reaching the poor families in, Mali, and Bangladesh. In South Africa, inequality was not significant. The most important characteristics that create variation in full vaccination status were maternal age, occupation, number of children in the house, frequency of watching television, and wealth of the household. A further study including multiple countries from each economic category would help to better summarize the inequality, as well as to target an intervention at different economic categories.

Supporting information