Antiviral Drugs for Post-Exposure Prophylaxis Against Influenza A or Influenza B

Key Messages

What Is the Issue?

• Antiviral medications for influenza can be used after exposure but before symptom onset to reduce the occurrence of symptomatic and asymptomatic influenza.
• There are several different antiviral medications available for preventing influenza after exposure (also known as post-exposure prophylaxis). It is important to understand their overall and comparative efficacy for treatment and stockpiling decisions.

What Did We Do?

• We conducted a rapid review of the recent evidence on the clinical efficacy and safety of different antiviral medications available in Canada for post-exposure prophylaxis.
• We searched key resources, including journal citation databases, and conducted a focused internet search for relevant evidence published since 2020.

What Did We Find?

• We identified 2 systematic reviews (SRs) of 12 randomized studies published in 2024. The included studies examined the efficacy of 3 antiviral medications (baloxavir, oseltamivir, and zanamivir) in preventing influenza infection. The reviews were generally well conducted.
• The findings show that these 3 antiviral medications are effective in reducing symptomatic influenza infection; however, the evidence on their impact on overall influenza and asymptomatic influenza infections is less clear.
• The evidence on the impact of these medicines on hospitalization and mortality was generally weak, with no strong conclusions. There is also little evidence of any additional adverse events (side effects) from these medicines.
• We found no evidence on peramivir for any of the outcomes.

What Does It Mean?

• The included studies support the efficacy and safety of 3 antiviral medications in post-exposure settings for influenza prevention. More evidence is needed to understand their impact on hospitalization and mortality.