The study aims to investigate the efficacy of favipiravir in high-risk COVID-19 patients. The study population includes symptomatic mild-to-moderate COVID-19 inpatients, within first 7 days of illness, who are 50 years old and above, and have 1 or more comorbidities. The study is designed as a randomised, open-label, multicenter clinical trial where the patients are randomised 1:1 to groups receiving favipiravir (5 days) versus no favipiravir.

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