**1. Introduction**

Immunization is one of the most cost-effective ways to protect populations from vaccine-preventable diseases. Consequently, ensuring universal access to immunization promotes population health and long-term prosperity [1,2]. Childhood immunization plays a key role in achieving 14 of the 17 United Nations Sustainable Development Goals (SDGs) [3], particularly SDG 3, 'Ensure healthy lives and promote well-being for all at all ages'. However, universal access to immunization should not be interpreted as a 'one size fits all approach'. There are population groups or individuals who will require local tailoring of services; failure to identify, acknowledge and address the barriers they face can lead to systematic inequities in immunization coverage. Immunization inequities contribute to accumulations of susceptible individuals in communities and thereby lead to outbreaks of vaccine-preventable diseases [4–6].

**Citation:** Datta, S.S.;

Martinón-Torres, F.; Berdzuli, N.; Cakmak, N.; Edelstein, M.; Cottrell, S.; Muscat, M. Addressing Determinants of Immunization Inequities Requires Objective Tools to Devise Local Solutions. *Vaccines* **2023**, *11*, 811. https://doi.org/10.3390/ vaccines11040811

Academic Editor: Pedro Plans-Rubió

Received: 28 February 2023 Revised: 28 March 2023 Accepted: 3 April 2023 Published: 6 April 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Monitoring and addressing immunization inequities are embedded in every regional and national immunization strategy in the World Health Organization (WHO) European Region (hereafter the Region). However, the countries in the Region nevertheless have difficulties in reaching and sustaining the 95% coverage target for the third dose of diphtheriapertussis-tetanus containing vaccine (DTP3) established by European Vaccine Action Plan 2015–2020 (EVAP) [7]. The factors that influence immunization uptake and those responsible for sub-optimal vaccination coverage at subnational or national level, are multiple and often context specific [8–11]. The European Immunization Agenda 2030 (EIA2030) seeks to build better health tomorrow in the Region through stronger immunization programmes today, by ensuring equity in immunization, providing immunization across the life course and devising local solutions to local challenges [12].

It is critical that the national and subnational health systems systematically address the local factors influencing the immunization inequities, and thereby achieve and sustain high vaccination coverage in the countries. Such an approach should include a continuous process of reviewing local-level immunization coverage data, which can guide national and subnational health systems in identifying areas of sub-optimal coverage and inform national immunization policy. However, to successfully address the reasons for sub-optimal vaccination in certain areas or populations, it is critical that local-level immunization stakeholders undertake measures through use of the available tools to identify who is not vaccinated and gather information on the local drivers of and barriers to immunization uptake by the population. Tailored, local-level interventions are needed to address the identified barriers that lead to local immunization inequities. To develop these interventions, immunization stakeholders at all levels, but especially at subnational or local health centre levels, need pragmatic guidance and tools. Aligned to the core principle of EIA2030 to devise local solutions to local challenges, we outline what can be done to empower especially the subnational immunization managers and functionaries of a health system to address immunization inequities and thereby contribute to the ethos of the SDGs: "leaving no one behind".

#### **2. Discussion**

#### *2.1. Suboptimal Immunization Coverage and Risks of Disease*

Relatively high immunization coverage in the Region over the past two decades has allowed it to sustain polio-free status since 2002 [13] and achieve significant progress in reducing the burden of measles, rubella, tetanus, diphtheria and other vaccine-preventable diseases [6]. However, routine immunization coverage still varies considerably among the Region's 53 countries, and among different populations and districts within them. In 2021, while the regional coverage with DTP3 was 94%, 25 countries (47%) reported DTP3 vaccination coverage of more than 95%, 15 (28%) reported coverage between 90% and 95%, 11 (21%) reported coverage between 80% and 90% and 2 (4%) countries reported coverage below 80% [14]. During the same year, 13 (25%) countries reported that between 1% and 52% of their subnational administrative units attained DTP3 coverage of less than 80% [15]. A similar pattern was observed for the first dose of measles-containing vaccine (MCV1) in the Region in 2021: while the regional coverage was 94%, 28 countries (53%) reported less than 95% MCV1 coverage. These variations in immunization coverage between, and within, countries indicate that the unvaccinated and under-vaccinated populations in the Region are at high risk of vaccine-preventable diseases; where there are higher numbers of unvaccinated individuals concentrated in populations or groups, there is a higher potential for outbreaks or the re-emergence of vaccine-preventable diseases.
