**1. Introduction**

Between 2020 and 2021, the COVID-19 pandemic severely strained health systems across countries, leaving millions without access to essential healthcare services. Routine Immunization programs experienced a 'double burden' of challenges due to the COVID-19 pandemic and associated disruptions and to the subsequent COVID-19 vaccination efforts shifting often limited resources away from routine services. The latest World Health Organization (WHO) and United Nations Children's Fund (UNICEF) estimates suggest that 25 million children missed routine vaccinations in 2021, six million more than in 2019 and the highest number witnessed in nearly two decades.

Recovering from this sobering setback requires a united push on several fronts. Intensifying the catch-up of routine immunization services is critical to reach children left behind

**Citation:** Athiyaman, A.; Ajayi, T.; Mutuku, F.; Luwaga, F.; Bryer, S.; Giwa, O.; Mngemane, S.; Edwige, N.N.; Berman, L. Recovering from the Unprecedented Backsliding in Immunization Coverage: Learnings from Country Programming in Five Countries through the Past Two Years of COVID-19 Pandemic Disruptions. *Vaccines* **2023**, *11*, 375. https:// doi.org/10.3390/vaccines11020375

Academic Editors: Ahmad Reza Hosseinpoor, M. Carolina Danovaro, Devaki Nambiar, Aaron Wallace and Hope Johnson

Received: 14 November 2022 Revised: 16 December 2022 Accepted: 26 December 2022 Published: 7 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/).

during the pandemic and bridge large immunity gaps in countries. At the same time, we must strengthen the resilience of immunization systems to withstand future pandemics if we hope to achieve the goals of Immunization Agenda 2030 to ensure vaccinations are available for everyone, everywhere by 2030.
