**5. Conclusions**

Recognizing where exceptional progress in reducing zero-dose children has occurred is the first step toward better understanding what countries did to attain such improvements. Such insights then can inform strategy adaptions to other settings, and further reinforce successful strategies in places that achieved large reductions historically but still have large populations of unvaccinated children today. Characterizing pathways to greater vaccination equity, as well ensuring mechanisms by which effective knowledge translation and cross-country learning can be supported, will strengthen efforts toward ensuring all children can fully benefit from vaccines.

**Supplementary Materials:** The following supporting information can be downloaded at: https://www. mdpi.com/article/10.3390/vaccines11030647/s1, Table S1. Initial countries considered for the present

analysis but were excluded for not meeting inclusion criteria; Figure S1. National and subnational trends in the prevalence of no-DTP children, 2000-2019, in the Democratic Republic of the Congo (A), Ethiopia (B), India (C), Bangladesh (D), and Burundi (E); Figure S2. Subnational no-DTP prevalence in Nigeria (A) and Ethiopia (B), 2000–2019.

**Author Contributions:** Conceptualization and Methodology: N.F., G.C.C., G.I., D.E.P. and H.W.R. Formal Analysis: N.F. Writing—Original Draft Preparation: N.F.; Writing—Review and Editing: N.F., G.C.C., G.I., D.E.P. and H.W.R. Visualization: N.F. and D.E.P. Supervision: G.I. and D.E.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Vaccine estimates used in this analysis are currently unpublished estimates from the Institute for Health Metrics and Evaluation (IHME). Data may be shared upon request to the corresponding author and IHME.

**Acknowledgments:** We thank Jonathan Mosser, Emily Hauser, Sam Rolfe, and Jason Nguyen from the Institute for Health Metrics and Evaluation for providing the estimates of childhood vaccination used in this study. We thank the following individuals from Gates Ventures, for their programmatic support and assistance: Patrick Y Liu, Jordan-Tate Thomas, Rowan Hussein, and Ryan Fitzgerald.

**Conflicts of Interest:** N.F., G.I. and D.E.P. are paid employees of Gates Ventures, which coordinates the Exemplars in Global Health (EGH) program. N.F., G.I., and D.E.P. previously worked at the Institute for Metrics and Evaluation (IHME): September 2008–2011 and February 2013–June 2022 for N.F.; August 2014–July 2020 for G.I.; and June 2009–February 2019 for D.E.P., G.C.C. and H.W.R. are employed by Gavi, the Vaccine Alliance. They had total freedom to express their views, which do not necessarily reflect those of Gavi.

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