Inclusion Criteria:  Patients are eligible to be included in the study only if they fulfil ALL the following criteria: RT-PCR confirmed COVID-19 cases Aged 50 years and above, AND have one or more co-morbidities Within the first 7 days of illness (from symptom onset) Mild to moderate clinical severity  Exclusion Criteria:  Asymptomatic stage 1 patients Patients with SpO2 less than 95% without oxygen therapy Patients who needs oxygen supplements Patients with concomitant bacterial or fungal infection (confirmed by culture) prior to initiation of study Patients with congestive heart failure Patients with severe hepatic impairment (>Grade 3: ALT >10 times of upper normal limit) Impaired kidney function (creatinine clearance according to Cockcroft-Gault formula less than 30 ml/min) at the time of screening. Malabsorption syndrome or other clinically significant gastrointestinal disease that may affect absorption of the study drug (non-correctable vomiting, diarrhea, ulcerative colitis, and others). Pregnant or nursing women or women planning pregnancy. Female patients who cannot consent to contraceptive use of oral contraceptives, mechanical contraceptives such as intrauterine devices or barrier devices (pessaries, condoms), or a combination of these devices from the start of favipiravir administration to 7 days after the end of favipiravir administration Male patients whose partner cannot agree to use the contraception method described in (9) Patients with a history of gout or on treatment for gout or hyperuricemia Patients receiving immunosuppressants Patients who received interferon or drugs with reported antiviral activity against COVID-19 (hydroxychloroquine sulfate, chloroquine phosphate, lopinavir-ritonavir combination) within 7 days of illness. Patients in whom this episode of infection is a recurrence or reinfection of COVID-19 infection Patients who have previously received favipiravir Patients who are not able to provide written consent by themselves Other patients judged ineligible by the principal investigator or sub-investigator