Network Meta-analysis: Oseltamivir Fails to Improve Key Outcomes in Nonsevere Influenza

Background: Influenza causes significant respiratory morbidity and can lead to severe complications, especially in high-risk individuals. Current guidelines endorse antiviral therapy, yet the evidence for reducing mortality, hospital admission, and symptom duration in nonsevere cases remains controversial. Recent recommendations have often focused on neuraminidase inhibitors (e.g., oseltamivir), despite uncertainties regarding clinical impact and adverse effects. An editorial accompanying this study underscores the need to reexamine routine antiviral use, especially oseltamivir, given minimal benefit observed in outpatient populations.

Objective: To assess and compare the efficacy and safety of direct-acting antiviral medications (baloxavir, oseltamivir, laninamivir, zanamivir, peramivir, umifenovir, favipiravir, and amantadine) in treating patients with nonsevere influenza.

Methods: This systematic review and network meta-analysis included 73 randomized clinical trials (N=34,332) that evaluated antivirals vs placebo, standard care, or another antiviral. Eligible studies enrolled nonhospitalized patients with confirmed or suspected influenza. Outcomes included mortality, hospital admission, time to symptom alleviation, adverse events, and emergence of antiviral resistance. Risk of bias was assessed with a modified Cochrane tool, and the certainty of evidence was rated using the GRADE approach. Pooled estimates were generated with a frequentist random-effects model, focusing on both absolute risk differences and relative measures.

Results:

• Mortality: Across all antiviral agents, there was high-certainty evidence of little or no effect on mortality in both low-risk and high-risk patients compared with standard care or placebo.
• Hospital Admission: In low-risk patients, none of the antivirals significantly altered admission rates (high certainty). In high-risk patients, oseltamivir had little or no effect on hospitalization (high certainty), whereas baloxavir may reduce admissions (low certainty).
• Time to Alleviation of Symptoms: Baloxavir shortened symptom duration by approximately one day (moderate certainty) without increasing adverse events. Oseltamivir and zanamivir likely produced smaller decreases (<1 day; moderate certainty). Umifenovir may also shorten symptoms (low certainty).
• Adverse Events: Baloxavir did not increase treatment-related adverse events (high certainty) but may lead to viral resistance in around 10% of cases (low certainty). Oseltamivir probably increases adverse events such as nausea and vomiting (moderate certainty).
• Serious Outcomes (ICU Admission, Duration of Hospitalization): Data were limited, with uncertainty regarding meaningful reductions in these measures.

Conclusions: Baloxavir may reduce hospital admissions for high-risk patients and significantly shorten symptom duration without notable treatment-related adverse events. Oseltamivir shows little effect on mortality or hospitalization for nonsevere influenza, with only modest (likely not clinically important) reductions in symptom duration and a higher rate of adverse events. Other antivirals either demonstrate uncertain clinical benefits or likely provide no major advantages in this patient population.

Implications for Practice: These findings suggest that routine use of oseltamivir for outpatients with nonsevere influenza should be reconsidered, especially in low-risk groups. Baloxavir appears favorable for high-risk patients, though clinicians should monitor potential drug resistance. Given the minimal impact on major outcomes and the cost considerations, prescribers should weigh the benefits and harms of these antivirals, aligning treatment decisions with patient risk profiles and clinical judgment.

Study Strengths and Limitations: Strengths include a comprehensive search, large pooled population, and rigorous GRADE-based analysis of certainty. Limitations involve low event rates for hospital admissions and mortality, limiting power for certain outcomes, and sparse data on some antivirals (e.g., amantadine). Additionally, few trials reported ICU admissions or mechanical ventilation needs, restricting conclusions about severe complications.

Future Research: Further high-quality studies should evaluate patient-important outcomes such as mechanical ventilation and severe complications in diverse populations. Investigations into combination strategies, alternative dosing, and resistance patterns would help clarify the long-term viability of baloxavir and other antivirals, particularly in high-risk cohorts.

Reference:

1. Gao Y, Zhao Y, Liu M, et al. Antiviral Medications for Treatment of Nonsevere Influenza: A Systematic Review and Network Meta-Analysis. JAMA Internal Medicine. Published online January 13, 2025. DOI: http://doi.org/10.1001/jamainternmed.2024.7193
2. Baghdadi JD, Grady D, Morgan DJ. The Limited Role for Antiviral Therapy in Influenza. JAMA Internal Medicine. Published online January 13, 2025. DOI: http://doi.org/10.1001/jamainternmed.2024.7258