Abstract: Benefits of Treatment With Favipiravir in Hospitalized Patients for COVID-19: a Retrospective Observational Case-control Study Anıl Uçan (  anil.ucan@saglik.gov.tr ) Ministry of Health https://orcid.org/0000-0001-8771-6121 Pamir Çerçi Eskisehir State Hospital: Eskisehir Devlet Hastanesi Serdar Efe Eskisehir State Hospital: Eskisehir Devlet Hastanesi Hakan Akgün Eskişehir Devlet Hastanesi: Eskisehir Devlet Hastanesi Ahmet Özmen Eskişehir Devlet Hastanesi: Eskisehir Devlet Hastanesi Aysel Yağmuroğlu Eskişehir Devlet Hastanesi: Eskisehir Devlet Hastanesi Muzaffer Bilgin Osmangazi University: Eskisehir Osmangazi Universitesi Deniz Avcı Kayseri City Hospital: TC Saglik Bakanligi Kayseri Sehir Egitim ve Arastirma Hastanesi Research Keywords: Severe acute respiratory syndrome coronavirus 2, Pneumonia, Favipiravir, Hydroxychloroquine, Antiviral therapy Posted Date: February 4th, 2021 DOI: https://doi.org/10.21203/rs.3.rs-175340/v1 License:   This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License Page 1/17 Abstract Background: Although more than a year past since COVID-19 was defined, there is no specific treatment yet. Since COVID-19 management differs over time, it is hard to determine which therapy is more efficacious. In this study, we aimed to evaluate the efficacy of the regimen with Favipiravir (FPV) and determine if the timing of FPV addition offers any improvement. Methods: A retrospective observational case-controlled cohort study was performed between March and Sep-tember 2020, including adults with COVID-19 in a single-center in Turkey. We categorized patients into age-sex matched three groups, group 1 (n=48) and group 2 (n=48) included patients treated with the combination of FPV plus Hydroxychloroquine (HQ) early and late, respectively. Group 3 (n=48) consisted of patients on HQ monot-herapy. In Group 2, if the respiratory or clinic condition had not improved sufficiently, FPV was added on or after day 3. Results: We found that starting FPV early had an impact on PCR negativity and the progression of the disease. 'No progression' was defined as the absence of a new finding in the control radiological examination and the absence of accompanying clinical deterioration. Also, the decrease in C-reactive protein (CRP) was greater in Group 1 than Group 3 (p <0.001). However, we found that early initiation of FPV treatment did not have a posi-tive effect on the estimated survival time. Conclusions: According to this retrospective study results, we believe that for better clinical outcomes, FPV treatment should be started promptly to enhance antiviral effects and improve clinical outcomes. Introductions The SARS-CoV-2 virus, most of its clinical manifestations causing a respiratory illness with noncharacteristic symptoms, was observed in a group of patients with unknown cause pneumonia in Wuhan, China, in December 2019 (1). By the time, the cause of this disease is understood to be a new coronavirus. It was temporarily named the new coronavirus 2019 (nCoV) by the World Health Organization (WHO). In February 2020, the emerging clinical manifestation was redefined as "COVID − 19" (coronavirus disease 2019). Since the beginning of the pandemic, the new coronavirus has caused over 79 million reported cases and more than 1.7 million deaths worldwide, as of December 29, 2020 (2). In COVID-19, there is an incubation period of approximately 5.2 days between the appearance of symptoms and..