Social inequities in vaccination coverage among infants and pre-school children in Europe and Australia – a systematic review

Achieving equity in child health is an important public health challenge on the global level, but also within high-income countries. Equitable access to preventive health services for children has a potential to reduce health inequities during childhood and later in life [1]. A key preventive service in the first years of life is the provision and delivery of vaccinations. Despite significant improvements over the past decades, herd immunity, i.e. the state in which sufficient percent of the population is vaccinated to prevent the spread of disease, is not reached in some high-income countries [2]. Low uptake of vaccine is often associated with persistent social inequities in vaccine uptake [3]. In order to prevent transmission of infectious diseases, herd immunity needs to be reached not only at national level but also within all social strata to prevent the creations of subpopulations with particularly low vaccine coverage where epidemics can start.

Most countries in the European Union, as well as Australia, have publicly funded vaccination programs for children, which aim to overcome financial barriers for families to accessing vaccinations. However, the structure of primary care services and the organization of preventive care may also matter and differ substantially across Europe and Australia. This provides an opportunity for comparative analysis [4].

Based on a classification by Borgueil et al. [5], the organization of primary care services (PCSs) can be grouped into: hierarchical and non-hierarchical. PCSs with a hierarchical model work under government control and are governed by de-centralized authorities. In countries with this model, governments provide, regulate and fund health services with relatively low freedom for practitioners to set up health care clinics. Spain, Sweden, United Kingdom and the Netherlands are examples of countries that traditionally have had a hierarchical model. PCSs with a non-hierarchical model are characterized by the coexistence of different modes of organization, limited government control and a predominance of solo practitioners with a great degree of freedom where to set up health care clinics. Germany, Austria and France are examples of countries with a non-hierarchical model of primary care services.

Another important distinction across countries is the organization of preventive healthcare services for preschool children. In some contexts (such as in Australia, Netherlands and Sweden), a separate organization is solely responsible for preventive services for children, “well-baby clinics”, where as in others, preventive health services are integrated within the regular primary care services that also provide curative care (such as in United Kingdom). The Well-baby clinics are generally built around a child or public health nurse that work within a team of other child health professionals [6]. These nurses typically schedule visits with families at the clinic according to a preset age dependent schedule, provide telephone counselling and allow for some on-demand visits.

The provision of equitable preventive services depends on multiple structural and organizational factors. Much attention has been paid to the roles of micro-level interventions within one health care system such as the implementation of reminder/recall services, outreach programs, and educational programs for parents and healthcare workers [7]. Factors on the macro level of the national health care system, however, have not been much investigated. Therefore, there is a need to take a broader approach and study socioeconomic distribution of vaccination coverage with a focus on structural and organizational factors of PCSs for children.

The aim of this study was to systematically review the existing empirical studies on socio-economic patterns of vaccination coverage for infants and pre-school children in Europe and Australia and to analyse the findings in the light of structural and organizational differences in primary care at the national level. We hypothesize that having a hierarchical model of primary care organization and presence of well-baby clinics will lead to more equitable services and thus smaller differences in vaccination coverage between socio-economic groups.

A systematic literature search was made on July 20, 2017. The following selection criteria, based on Prisma guidelines [8], were used. The search was updated on April 20, 2018 and no new studies were found.

A total of 8927 unique articles were screened by title and abstract, 108 articles were found as eligible for reading in full-text after which 17 studies were selected for data extraction. Two articles from Belgium [12, 13] had overlapping data sets and were therefore merged into one study, in the process of data synthesis. The risk of bias was assessed to ensure the quality of included studies (Additional file 2). High risk of a bias, in a Greek study of preschool children in nurseries, led to the exclusion of one study [14] leaving 15 studies in the final synthesis of the results. A summary of this process is shown in Fig. 1.

In this systematic review, we have investigated the social patterns of vaccine uptake in Europe and Australia in relation to their organisation of primary care services. The diversity of social indicators used in the studies we identified did not allow us to perform a meta-analysis, but nonetheless some tentative patterns emerged. All studies in primary care models with well-baby clinics showed high overall vaccination coverage and six out of the seven studies demonstrated equitable uptake of vaccination. Lowest levels of overall vaccination coverage and relatively wider gaps based on parental education and occupation were observed in Greece and France, countries with non-hierarchical primary care organization that did not have well-baby clinics. Studies from Germany and Italy, however, countries with a non-hierarchical model of primary care, showed a high coverage and quite equitable uptake of vaccine, indicating that it is possible to obtain satisfactory vaccine uptake also with a non-hierarchical model of primary care.

Our analysis suggests that providing preventive health services in a special organisation within primary care may increase equity in vaccine uptake for preschool children. Although we acknowledge that there can be multiple factors in play, we believe well-baby clinics deserve special attention due to its potential in meeting the quality criteria for primary care services suggested by Starfield [27]. The four quality criteria: access, longitudinality, comprehensiveness and coordination can be used as a framework to understand the mechanisms behind the role of the well-baby clinics. It seems likely that this special organization facilitates easy access when vaccination does not have to compete with other priorities and provides a continuity in care that leads to a trustful relation between health care provider and family by repeated visits to the same nurse from the neonatal period until school entry. Trust to the healthcare providers has previously been found to have positive association with vaccination uptake [7, 23]. Compared to more fragmented models of preventive health where different health organizations deliver different services, the well-baby clinics provide a comprehensive platform for various preventive interventions and coordinate referrals to other health care providers motivated by screening procedures or negative vaccine reactions.

Previous research on interventions to reduce social inequalities in vaccination uptake have primarily focused on their implementation within one specific primary health care model, for example the NHS model in the UK. A recent systematic review found complex, and locally designed, interventions to be more effective in buffering disadvantages [7]. To some extent, these interventions resulted in a model of preventive care that is similar to the well-baby clinics since they enabled easy access and continuity in relation between healthcare provider and family. This suggests that taking a broader perspective might be beneficial in future developments in this field, where changes in the overarching primary care model, may be a more effective way to improve equity in vaccination uptake than to implement small-scale interventions within the existing primary care models.

The potential of well-baby clinics as a platform for targeted interventions has been shown in a recent Swedish intervention study [28, 29]. In this study, guided by a “proportionate universalism” approach [30], all families with infants in a disadvantaged neighbourhood were offered an intensified home visiting program by the well-baby clinic in collaboration with the social services in the area. The preliminary outcomes were promising with diminishing inequities in levels of vaccination coverage as one result [28].

Primary health care organizations that are based on the non-hierarchical model, such as those of Belgium, France, Greece and Germany, all provide a considerable freedom for primary care physicians to choose their area of practice; and there is comparatively limited influence of the national or regional state on its regulation and financing. Our systematic review shows that this type of health care organization in some countries is associated with considerably lower levels of overall vaccination coverage and higher social inequities with respect to parental occupation and education, but not in all countries with this model. France is an example of such a model with a low uptake. The French model is dominated by privately owned clinics and requires parents to buy the vaccination themselves with co-payments, which are later compensated by the government. These are possibly the two main driving forces for the low vaccination levels [31]. Italy is an example of a country with a similar primary model that has succeeded in obtaining a high uptake of vaccine by having an ambitious national vaccine policy [32].

Health care reform is currently underway in many European countries with a National Health Service, such as the UK, Spain and Sweden. One major shift due to the reforms is facilitation of the establishment of new private outpatient practices reimbursed by public funds at locations chosen by the health care professionals themselves. The changes also include increases in the proportion of private providers, application of market-based mechanisms, the promotion of a patient choice agenda and changes to resource allocation systems. Thus, the reforms are moving these primary care models closer to the non-hierarchical model. In countries with this model, studies in the adult population have shown that such changes lead to increased inequity in utilisation of primary care [33]. Consequences of these changes for equity in children’s access to preventive care should routinely be monitored.

When analyzed through a lens of structural and organizational factors, our review found some evidence for the role of well-baby clinics in providing more equitable vaccination services for children. Countries with well-baby clinics showed higher overall rates of vaccination, and there were less social inequities. Lowest vaccination coverage rates and high gaps due to parental occupation and education were observed mostly in systems with non-hierarchical systems that also lacked well-baby clinics.

The analysis of the results was greatly hampered by low number of studies that examine social inequities in vaccination uptake in Europe. This knowledge gap shows us where more research and monitoring is needed to inform primary care models for children with regards to equity.