Effectiveness of Favipiravir monotherapy in the treatment of COVID-19: real world data analysis from Thailand

BACKGROUND: Previous studies showed that Favipiravir, a selective viral ribonucleic acid dependent-ribonucleic acid polymerase inhibitor, exhibited a trend of clinical improvement within 14 days and promoted viral clearance by day 7, without reduction of mortality rate in COVID-19. METHODS: During the COVID-19 pandemic, Department of Medical Services (Thailand) formulated National Clinical Treatment Guidelines for COVID-19 and approved Favipiravir to eight medical centres. After treatment with Favipiravir monotherapy, we compared real-world data analysis to supportive treatment without antiviral agents. FINDINGS: We analysed 12,888 COVID-19 patients between June 1, 2021, and July 31, 2021. This group study excluded 66 asymptomatic and 4634 COVID-19 patients treated with other antiviral agents. The 4896 mild, 2357 moderate, and 935 severe COVID-19 patients were analysed. All patients neither had previous SARS-CoV-2 infection nor received an mRNA vaccine during study period. Favipiravir monotherapy reduced the 28-day mortality risk in severe COVID-19 by relative risk (RR) = 0.72 (95% CI 0.58–0.91 P = 0.006) after adjustment for aging and hypertension. However, in mild and moderate COVID-19, Favipiravir monotherapy did not significantly reduce 28-day mortality risk by RR = 0.59 (95% CI 0.06–5.43 P = 0.65) after adjustment for aging, and RR = 0.60 (95% CI 0.32–1.13 P = 0.11) after adjustment for aging and obesity, respectively. In the patient with recovery, Favipiravir monotherapy exhibited a shortening time to recovery when compared to supportive treatment without antiviral agents (mean ± SD by 9.6 ± 7.1 vs. 12.9 ± 7.6 days: P < 0.0001, 10.0 ± 5.9 vs. 12.4 ± 5.3 days: P < 0.0001, and 11.2 ± 7.8 vs. 13.1 ± 8.0 days: P < 0.0001 in mild, moderate, and severe COVID-19 respectively). INTERPRETATION: Real-world data analysis showed that favipiravir monotherapy was superior to supportive treatment without antiviral agents in shortening the recovery time in surviving patients and significantly reducing 28-day mortality risk in severe COVID-19. FUNDING: 10.13039/501100004397Department of Medical Services, Ministry of Public Health, Thailand.