**6. Conclusions**

The findings presented clearly demonstrate the evidence of a decline in routine immunization coverage in urban and peri-urban settings; as such, the need to target and focus context-specific catch-up and recovery strategies to bring back routine immunization performance on track. However, they also elucidate the need to further explore and examine determinants of low immunization coverage in urbanized areas, particularly in low- and middle-income countries. There are relatively few papers that estimate the magnitude of backsliding caused by COVID-19 in urban and peri-urban settings, in these priority countries, as well as a dearth of papers focusing on key issues affecting routine immunization in these settings and effective pro-equity strategies to address those keys issues in immunization recovery. While the COVID-19 pandemic has only been affecting immunization coverage in these areas for almost three years, the backsliding caused by this international disruption has proved detrimental, particularly toward reaching the goals set by IA2030.

Over the many different contexts explored through the review, different factors have been shown to affect immunization coverage in urban and peri-urban areas. It is essential that each context is specifically examined for services to be designed and tailored to the communities affected by the lack of access to these services. Innovations in interventions will be needed to build a better pro-equitable system of immunization for these areas. Rapid global urbanization makes addressing urban immunization challenges an essential and immediate priority in order to keep up with the demands placed on global immunization systems in the 21st century.

**Author Contributions:** I.D. conceived the initial idea and drafted the frame of the paper. I.D. and R.V.B. conducted the review of the literature. I.D., R.V.B. and A.I. completed various sections of the paper. A.R., I.H., D.A., N.D. and S.V.S. provided input and critical review to various sections of the paper and in the finalization of the paper. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research is funded in part by the Gavi, the Vaccine Alliance through Grant SC220417 to UNICEF.

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

**Informed Consent Statement:** Studies included in this review obtained informed consent from subjects where applicable.

**Data Availability Statement:** All data and publications used are referenced and available in the related databases.

**Acknowledgments:** The Urban Immunization Working Group is an extra-organizational group facilitated by UNICEF, comprising experts and academics from several different organizations. Thanks go to staff from UNICEF, WHO, University of Oxford, Bill and Melinda Gates Foundation, John Snow, Inc. and Johns Hopkins Bloomberg School of Public Health, who contributed to this review. Additionally, thanks to other members of the working group for their contributions towards improving immunization in urban contexts.

**Conflicts of Interest:** The authors declare no conflict of interest.
