**1. Introduction**

While global immunisation coverage has improved monumentally since the 1980s, progress in increasing coverage for different antigens has slowed or stalled over the last several years and has even declined during the COVID-19 pandemic [1,2]. Of particular concern are children who have not received any routine vaccination, referred to as zero-dose (ZD) children. These children are defined operationally by the Immunization Agenda 2030 (IA2030) as those who have not received a first dose of the diphtheria, tetanus, and pertussis (DTP1) vaccine in their first year of life [3]. With the COVID-19 pandemic straining health systems and severely impacting routine immunisation services in many countries, the number of ZD children—estimated at 14 million in 2019—increased by 34% globally in

**Citation:** Ducharme, J.; Correa, G.C.; Reynolds, H.W.; Sharkey, A.B.; Fonner, V.A.; Johri, M. Mapping of Pro-Equity Interventions Proposed by Immunisation Programs in Gavi Health Systems Strengthening Grants. *Vaccines* **2023**, *11*, 341. https:// doi.org/10.3390/vaccines11020341

Academic Editor: Pedro Plans-Rubió

Received: 23 December 2022 Revised: 17 January 2023 Accepted: 1 February 2023 Published: 2 February 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/).

2021, when there were approximately 18.2 million ZD children [4]. Of these, 12.5 million (68%) lived in one of the 57 Gavi-supported countries1 [4]. Gavi-supported countries are countries that are eligible to apply for Gavi support, determined by their national income. In 2020, countries with a Gross National Income (GNI) per capita equal to or less than US \$1630 over the last three years were eligible for support [5]. It is thus now more critical than ever to reverse this trend and reach the remaining unimmunised children. Reaching ZD children and missed communities, which are operationally defined as being home to clusters of ZD and under-immunized children, is a central component of both IA2030 and Gavi, the Vaccine Alliance's strategic plan for 2021–2025 (Gavi 5.0), with a vision of "leaving no one behind with immunisation" [3,6]. Reaching these populations is expected to bring more children to full immunisation and increase access to primary health care [7,8]. This, in turn, is an important component towards achieving universal health coverage, especially in low- and middle-income countries (LMICs) [9].

Even though the concept of equity has been guiding global immunisation efforts and was already a key principle of the Gavi 4.0 strategy (2016–2020), the stalled progress in recent years and backsliding of routine immunisation during the pandemic have highlighted the inability of traditional interventions to maintain high coverage and reach the approximately 15% of children worldwide who remain unvaccinated with DTP1 [2]. Adding to the complexity is that ZD children are among the world's most vulnerable populations and are believed to face complex and overlapping deprivations, with several proximal, distal and greater contextual determinants (e.g., gender, conflict, and health systems factors) at play. Indeed, they often have a lower socioeconomic status, belong to religious or ethnic minorities, suffer from childhood malnutrition and are children of mothers with lower levels of education and empowerment, making them more socially and economically disadvantaged [9–13]. Along these lines, the Equity Reference Group for Immunisation (ERG) has emphasized and called for a greater focus on four key areas to reach ZD children, namely conflict-affected, urban poor, and remote rural areas as well as gender-related barriers. While those overlapping vulnerabilities make it particularly challenging to reach ZD children with vaccination, the potential benefits to children's' health and development, to their families and communities, and to societies, are immense.

While the concept of "zero-dose" children has existed for several years [14], it only recently came to the forefront of the attention of the global health community and there is still an important lack of knowledge about which interventions can be implemented to best reach them, how much they cost, and how to sustain progress. Understanding which interventions are already being implemented is one step towards building this evidence base. To the best of our knowledge, only one study has been published that explores this question. Dadari and colleagues mapped pro-equity strategies being implemented in thirteen Gavi-supported countries through review of Joint Appraisal (JA) reports from 2016 to 2019 [15]. JA reports are documents submitted to Gavi by countries every year detailing all Gavi-supported activities implemented, progress and performance. The authors found that all thirteen countries had in place over 250 interventions aiming to increase vaccine equity and concluded that further efforts should be made to do a similar mapping with other types of Gavi documents and across more countries to establish a more complete picture [15].

Building on this foundation, the current paper presents findings from a similar mapping in Gavi Health System Strengthening (HSS) proposals. These documents are particularly relevant because they are focused on achieving equitable immunisation coverage and have by far the largest envelope of all Gavi cash grants [16]. Indeed, as of December 2021, commitments for HSS support from 2000 to 2025 for all Gavi-supported countries amounted to US \$3005.4 million. In comparison, the next biggest funding lines were operational support with an envelope of US \$935.5 m and immunisation services support with US \$355.9 m [17]. In HSS proposals for the Gavi 4.0 strategy period, countries had to articulate how funds would be used and detail clear strategies to improve immunisation access and equity, though not specifically for zero-dose children since this only became a focus in Gavi

5.0. Proposals submitted to Gavi are reviewed and approved by an Independent Review Committee (IRC) comprising experts in different fields including public health, epidemiology, and economics. We reviewed these HSS proposals to document and learn more about the pro-equity interventions used by countries to improve immunisation equity and to understand how these investments can help us prioritise interventions moving forward.
