Zanamivir as prophylaxis

Inhaled zanamivir is an effective neuraminidase inhibitor for post-exposure prophylaxis (PEP) of seasonal influenza in community and household settings (1, 2):

• clinical trial evidence demonstrates a 79% protective efficacy in preventing secondary laboratory-confirmed influenza cases when administered as post-exposure prophylaxis to exposed household contacts for 10 days (1)
• current UK Health Security Agency (UKHSA) guidance and NICE technology appraisal TA158 support zanamivir PEP for individuals at high risk of severe complications following close contact with an index case during circulating seasons (2, 3)

Clinical Efficacy and Trial Evidence

Household Post-Exposure Prophylaxis Evidence

• high-level clinical trial data (randomized double-blind placebo-controlled study) confirms that inhaled zanamivir significantly reduces household transmission of influenza A and B (1)
• secondary case prevention: 10 days of post-exposure prophylaxis in exposed family members achieved 79% efficacy in preventing secondary clinical and laboratory-confirmed influenza cases compared to placebo (1)
• symptom severity reduction: contacts who developed influenza despite prophylaxis experienced milder overall illness duration and reduced viral shedding (1)

Indications and Clinical Prescribing Criteria

Primary Care Indications

• recommended for post-exposure prophylaxis in individuals in clinical at-risk groups or those with severe immunosuppression following close exposure (e.g., household or long-term care setting) to a suspected or confirmed index case (2, 3)
• initiation window: PEP should be started as soon as possible, ideally within 36 hours of contact with the index case (2, 3)

Dosing and Regimens

• standard post-exposure prophylaxis dosage: 10 mg (2 inhalations) once daily for 10 days via Diskhaler in adults and children aged 5 years and over (2, 3)
• severe immunosuppression: UKHSA guidance recommends PEP for severely immunosuppressed contacts following exposure regardless of seasonal influenza vaccination status (3)

Precautions and Administration

Clinical Considerations

• respiratory safety: avoid inhaled zanamivir in individuals with severe asthma or severe COPD due to the risk of acute bronchospasm and rapid bronchoconstriction (3)
• device operation: verify that the patient or carer possesses adequate inhaler technique to reliably operate the breath-actuated Diskhaler device (2)

Reference:

1. Hayden FG, Gubareva LV, Monto AS, et al. Inhaled zanamivir for the prevention of influenza in families. N Engl J Med. 2000;343(18):1282-1289.
2. National Institute for Health and Care Excellence (NICE). Oseltamivir, amantadine and zanamivir for the prophylaxis of influenza. NICE Technology Appraisal [TA158]. 2008 (reviewed 2014).
3. UK Health Security Agency (UKHSA). Guidance on use of antiviral agents for the treatment and prophylaxis of seasonal influenza. UKHSA Public Health Guidance. Updated October 2026.