Impact of the COVID-19 Pandemic on Influenza HospitalAdmissions and Deaths in Wales: Descriptive National TimeSeries Analysis

Background: The COVID-19 pandemic and the ensuing implementation of control measures caused widespread societaldisruption. These disruptions may also have affected community transmission and seasonal circulation patterns of endemicrespiratory viruses. Objective: We aimed to investigate the impact of COVID-19-related disruption on influenza-related emergency hospitaladmissions and deaths in Wales in the first 2 years of the pandemic. Methods: A descriptive analysis of influenza activity was conducted using anonymized pathology, hospitalization, andmortality data from the Secure Anonymised Information Linkage Databank in Wales. The annual incidence of emergencyhospitalizations and deaths with influenza-specific diagnosis codes between January 1, 2015, and December 31, 2021, wasestimated. Case definitions of emergency hospitalization and death required laboratory confirmation with a polymerase chainreaction test. Trends of admissions and deaths were analyzed monthly and yearly. We conducted 2 sensitivity analyses byextending case definitions to include acute respiratory illnesses with a positive influenza test and by limiting admissions tothose with influenza as the primary diagnosis. We also examined yearly influenza testing trends to understand changes intesting behavior during the pandemic. Results: We studied a population of 3,235,883 Welsh residents in 2020 with a median age of 42.5 (IQR 22.9-61.0) years.Influenza testing in Wales increased notably in the last 2 months of 2020, and particularly in 2021 to 39,720 per 100,000people, compared to the prepandemic levels (1343 in 2019). The percentage of influenza admissions matched to an influenzapolymerase chain reaction test increased from 74.8% (1890/2526) in 2019 to 85.2% (98/115) in 2021. However, admissionswith a positive test per 100,000 population decreased from 17.0 in 2019 to 2.7 and 0.6 in 2020 and 2021, respectively.Similarly, deaths due to influenza with a positive influenza test per 100,000 population decreased from 0.4 in 2019 to 0.0 in2020 and 2021. Sensitivity analyses showed similar patterns of decreasing influenza admissions and deaths in the first 2 yearsof the COVID-19 pandemic. Conclusions: Nonpharmaceutical interventions to control COVID-19 were associated with a substantial reduction in thetransmission of the influenza virus, with associated substantial reductions in hospital cases and deaths observed. Beyond the pandemic context, consideration should be given to the role of nonpharmaceutical community-driven interventions to reducethe burden of influenza