Jean Cyr Yombi,1 Halil Yildiz,1 Claire Beguin,2 Laurence Habimana2 1Department of Internal Medicine and Infectious Diseases, Cliniques Universitaires Saint-Luc, Brussels, 1200, Belgium; 2Department of Medical Informatics and Statistics, Cliniques Universitaires Saint-Luc, UCLouvain, Brussels, 1200, BelgiumCorrespondence: Jean Cyr YombiDepartment of Internal Medicine and Infectious Diseases, Cliniques Universitaires Saint-Luc, 10 Avenue Hippocrate, Brussels, 1200, BelgiumTel +3227641902Fax +3227641046Email Jean.yombi@uclouvain.beBackground: Preliminary reports described a reduction in non-COVID admissions during the first wave of the pandemic including some of critical diseases such as cancer, myocardial and cerebral infarction.Objective: The aim of our study was to evaluate the impact of the COVID-19 pandemic on non-COVID in-hospital admissions in a large academic center in Belgium.Materials and Methods: We performed a retrospective study of non-COVID-19 in-hospital admissions during the first two waves of the COVID-19 pandemic. The average number of admissions per week in 2020 has been compared to that of the same period in 2019 and 2018. Comparisons were made first for all admissions, then by disease groups, using the classification of APRDRG, and then by diagnoses using ICD-10-CM classification.Results: Overall in-hospital admissions were reduced by around 39% and 29% during the first and the second waves of the COVID-19 pandemic respectively compared to 2018 and 2019. No significant difference was found between the average number of admissions in the early-COVID and the pre-COVID baseline period during the two waves. The average number of admissions was significantly reduced in the peak-COVID period compared to the baseline (first wave: 332 versus 763 admissions/week, p< 0.01, − 57%; second wave: 496 versus 788 admissions/week, p< 0.01, − 37%), as well as in the late-COVID period compared to the baseline (first wave: 412 versus 763 admissions/week, p< 0.01, − 46%; second wave: 470 versus 788 ...