**5. Conclusions**

As the global immunization community works to fulfill the ambitious goals of IA2030, new strategies to reach zero-dose children and communities will be needed. Integrating immunization with other essential health services, as part of robust primary health care systems, has the potential to improve efficiency and achieve greater equity in health outcomes, particularly for communities that are most at risk. The potential benefits of integration—and the ideal strategies to plan and implement these efforts—are likely to vary from country to country. Spatial analyses of the overlap between gaps in immunization services and other key health indicators can help to define the potential for joint geographic targeting of integrated service delivery to help ensure a future where all people have equitable access to lifesaving vaccines.

**Supplementary Materials:** The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/vaccines11040802/s1, Supplemental Methods; Table S1: Ten countries with highest no-DTP counts in 2019 and indicator data availability details; Table S2: Surveys included in DTP modeling; Table S3: Surveys excluded from DTP modeling; Table S4: GATHER Compliance checklist; Table S5: Geospatial covariates used in modeling; Figures S1–S23: Country-specific AUC step plots; Figures S24–S46: Country-specific, all quartile overlap; Figure S47–S69: Countryspecific, highest quartile overlap; Figures S70–S73: Multi-indicator overlap of country-specific highest quartiles; Figures S74–S77: Multinational all quartile overlap by prevalence; Figures S78–S81: Multinational highest quartile overlap by prevalence; Figures S82–S85: Multinational all quartile overlap by counts; Figures S86–S89: Multinational highest quartile overlap by counts. References [49–52] are cited in the Supplemental Methods.

**Author Contributions:** E.H. and J.F.M. conceptualized the project. E.H., S.R. and J.Q.N. participated in data curation, and E.H. conducted the formal analysis and investigation. E.H. and J.F.M. developed the methodology. E.H. contributed to software development. J.F.M. supervised the project. J.F.M. provided the validation of the results. E.H. created visualizations. E.H. and J.F.M. wrote the original draft, and S.R., O.N., J.Q.N. and N.F. were involved in the critical review, commentary, and revision during the writing process. E.H., S.R., J.Q.N. and J.F.M. had full access to and verified the underlying data used to generate the estimates presented in this article. All other authors had access to and reviewed the estimates as part of the research evaluation process, which included additional formal stages of review. The corresponding author had final responsibility for the decision to submit for publication. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by grants from the Bill & Melinda Gates Foundation (OPP1152504 and INV-037425) and Gavi (MEL 11507 5 22).

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The findings of this study are supported by data available in public online repositories and data publicly available upon request of the data provider. Details of data sources and availability are publicly available in the Global Health Data Exchange (https://ghdx. healthdata.org/record/ihme-data/dtp-vaccines-zerodose-overlap). All computer code is available online and can be found at (https://github.com/ihmeuw/vaccines-zerodose-overlap).

**Acknowledgments:** We acknowledge, with gratitude, the time, expertise, and effort of the survey teams who gathered the data used to inform these modeled estimates, as well as all the participants in these surveys.

**Conflicts of Interest:** IHME is primarily funded by the Bill and Melinda Gates Foundation (BMGF). J.F.M., E.H., O.N., J.Q.N. and S.R. additionally report receiving funding from BMGF and Gavi. NF has received funding from Gates Ventures since June 2020, for work around childhood vaccination and vaccine delivery in low- and middle-income countries.

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