**1. Background**

Complex emergencies and natural disasters are associated with outbreaks of infectious diseases due to disruptions in health service delivery, including vaccination and nutrition [1]. Although there is limited literature on the impact of pandemics on essential health service delivery, the COVID-19 pandemic forced countries to observe social isolation, physical distancing, lockdowns, curfews, and quarantines. This may have posed a population health risk similar to the case of complex emergencies and natural disasters. Since 2019, the SARS-CoV-2 virus has rapidly spread from China, infecting over 650 million people, with 6.6 million deaths recorded globally as of 22 December 2022 [2].

The abrupt and rapid progression of the COVID-19 pandemic has caused significant disruptions in essential health service delivery in many countries, reversing past efforts to improve health indicators [3–5]. Indeed, according to the third round of the global pulse survey on the continuity of essential health services during the COVID-19 pandemic, over 90% of countries reported a serious continuous disruption in the delivery of essential health services [6]. Moreover, 53% of countries reported persistent disruptions in primary health care, with about 40% experiencing increased backlogs during the second half of 2021 [6]. These disruptions are mainly due to decreased care seeking in 25% of countries, but also unintended disruptions resulting from the lack of healthcare resources and intentional service delivery modifications in one-third of surveyed countries [6]. Moreover, a systemic review suggested a significant decline in vaccination coverage due to COVID-19, leading to a four-fold increase in polio cases in polio-endemic countries [7]. According to the authors, factors contributing to the observed decline include: fear of being exposed to the virus at healthcare facilities, restriction on city-wide movements, a shortage of workers, and diversion of resources from child health to address the pandemic, among others [7].

Cameroon, with an estimated population size of 27 million in 2022, has recorded over 120,000 COVID-19 cases and about 2000 COVID-19-related deaths, yet the reported national childhood routine vaccination coverage seems to have improved compared to the pre-COVID-19 period [2]. For instance, the first dose of the diphtheria, tetanus, pertussiscontaining vaccine (DTP-1) coverage increased by almost 2 percentage points (pp), rising from 85.4% in 2019 to 87.7% in 2020. Similarly, the third dose of DTP-containing vaccine (DPT-3) increased from 79.5% in 2019 to 81.2% in 2020. The observed increase in coverage suggests an increased access to, and utilization of, vaccination services during the COVID-19 pandemic [8]. This observation runs contrary to what has been reported by previous studies, which all showed serious disruptions in regards to other essential health system indicators. These authors reported serious disruptions in blood donation services, utilization of radiology units, geriatric consultations, pediatric hospitalization, and HIV service utilization, among others [9–15]. Another cross-sectional study assessed the impact of COVID-19 on immunization services in a single hospital setting in Cameroon—posing a problem for result generalizability [16]. In the current study we aimed to contribute by filling the existing knowledge gap concerning the impact of COVID-19 on routine childhood immunizations in Cameroon, which might be critical in ensuring continuous vaccination service delivery during public health emergencies. In addition, findings from this study will provide salient recommendations that could contribute to developing the COVID-19 recovery plan and informing policy on future pandemic preparedness and response.

#### **2. Methodology**

#### *2.1. Study Design and Setting*

This cross-sectional study compared childhood routine immunization access and utilization in the pre-pandemic period (2019) to the pandemic period (2020). The study considered aggregated secondary district-level data on routine childhood immunization from the District Health Information System (DHIS)-2. All districts found in the top two COVID-19 hotspot regions were considered for analysis.
