Table 2 Outcomes for patients with COVID-19 among eligible studies

Chen C [16]

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Clinical recovery rate of Day 7:

Favipiravir:

Total, 61.21%

Moderate, 71.43%

Severe or critical, 5.56% those in Arbidol:

Total, 51.67%

Moderate, 55.86%

Severe or critical, 0

No mortality both in favipiravir and arbidol groups

Lou Y [17]

Viral clearance in day 7

Favipiravir, 44%,

Baloxavir, 60%

Control, 50%

Viral clearance in day 14

Favipiravir, 77%,

Baloxavir, 70%

Control, 100%

Median days (IQR) to clinical improvement:

Favipiravir, 14 (6–38)

Baloxavir, 14 (6–49)

Control, 15 (6–24)

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Ivashchenko [18]

Viral clearance on day 5:

Favipiravir, 62.5%

SOC group, 30.0%

Viral clearance on day 10:

Favipiravir, 92.5%

SOC group, 80.0%

Chest CT improvement by day 15

Favipiravir, 90%

SOC group, 80%

.

Median days to body temperature normalization (< 37oC) were 2 days (IQR 1–3) in favipiravir group, while those in SOC group were 4 days (IQR 1–8).

Two patients on Favipiravir 1600/600 mg were moved to intensive care unit, received mechanical ventilation and later died.

Doi Y [19]

Viral clearance within 6 days were the Early treatments, 66.7%

Late treatments, 56.1%

Median days to viral clearance were Early treatments, 12.8 days

Late treatments, 17.8 days

Median days to hospital discharge:

Early treatments, 14.5 days

Late treatments, 20.0 days

Time to relieve from high fever (≥37.5 °C)

Early treatments, 2.1 days

Late treatments, 3.2 days

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Cai Q [20]

Median (IQR) days to viral clearance:

Favipiravir, 4 day (2.5–9)

Comparators, 11 (8–13) days

Chest CT improvement on day 9 were 56.3% in favipiravir group, and 35.6% in the comparator group.

Chest CT improvement on day 14 were 91.4% in favipiravir group, and 62.2% in the comparator group.

Logistic regression of changes in lung CT: antiviral therapy (OR, 3.190), and fever (OR, 3.622).

Cox regression of viral clearance

T lymphocyte count (HR, 1.002); Time form onset to treatment (HR, 1.217); FPV vs. LPV/RTV (HR, 3.434)

Rattanaumpawan [21]

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Clinical improvement for Day 7:

All patients, 42 (66.7%)

Clinical improvement for Day 14:

All patients, 54 (85.7%)

Clinical improvement for Day 28:

All patients, 57 (90.5%)

Day 14, 28 mortality rate, n (%)

all patients: 1 (1.6), 3 (4.8)

Required MV or ECMO, n (%)

Before favipiravir, 4 (6.3)

After favipiravir, 4 (6.3)

Duration of therapy, median (range),

Multivariate analysis revealed three poor prognostic factors for Day-7 clinical improvement [odds ratio (95%CI); p-value]: older age [0.94 (0.89–0.99); p = 0.04], higher baseline NEWS2 score [0.64 (0.47–0.88); p = 0.006], and lower favipiravir loading dose (≤45 mg/kg/day) [0.04 (0.005–0.4); p = 0.006].

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Duration of therapy, median (range), days:

clinical improvement on Day 7, 11.5 (2–16)

No clinical improvement on day 7, 12 (2–17)

Yamamura H [22]

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Died 1 patient due to DIC.

P/F changed very little over the first 6 days and then gradually recovered. IL-6 peaked on day 4 and decreased thereafter. Presepsin peaked on day 3, remained about the same until 6, and then decreased.

Doi K [23]

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1 patient who had a do-not-resuscitate order, died on ICU day 7.

No interruption of antiviral treatment occurred due to adverse drug reactions except for one patient who developed hyperkalemia on day 9 (by nafamostat mesylate).

All 11 patients had at least 33 days of hospital follow-up.

Seven patients were successfully weaned from MV [median duration of MV 16 days (IQR, 10 to 19 days)] and 9 and 7 patients were discharged from the ICU and the hospital, respectively

Murohashi K [24]

The mean time to first-time negative conversion of viral RNA was 18 days in 6 confirmed negative cases.

4 patients discharged; 6 patients have no oxygen at rest; 1 patient worsended on the day of admission, and was transferred to another hospital for ventilator management.

Çalik BaŞaran [25]

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Median (range) days to clinical improvement:

HQ alone, 1 (1–6)

HQ and AZ, 1.5 (1–11)

Favipiravir, 6 (1–20)

Median days of defervescence:

HQ alone, 1 (0–4)

HQ and AZ, 1 (0–11)

Favipiravir, 3 (0–8)

8.5% of patients were transferred to the ICU, 2.2% of patients died.

Median (range) length of hospital stay, were 2 (1–21) in HQ alone, 4 (1–15) in HQ and AZ, and 7.5 (2–24) days in favipiravir groups.

Yaylaci S [26]

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Among the examined hemarological parameters before and after favipiravir, RBC, hemoglobin level, hematocrit level, neutrophil count were decreased, and lymphocyte count, platelet count were increased with the statistical significance.