Comments from Expert Advisory Group and Key Points
- Patients presenting with respiratory symptoms should be managed according to the Acute Respiratory Infections guidance. See the HPSC website for further information on Acute Respiratory Infection - Health Protection Surveillance Centre (hpsc.ie).
- The expert advisory group recommend that the Guidance on the use of antiviral agents for the treatment and prophylaxis of influenza is consulted prior to making the final prescribing decision. It contains FAQ section and more detailed advice on various subgroups below.
- Two antiviral medications are recommended for use in the community in Ireland during the influenza season: oral oseltamivir and inhaled zanamivir. They are both antiviral neuraminidase inhibitors which have activity against seasonal influenza A and B.
- Antiviral medications are an important adjunct to vaccination and infection prevention and control practices in the control of influenza. Influenza vaccination and infection prevention and control practices are of the utmost importance in the prevention of influenza and are universally preferred over the administration of chemoprophylaxis.
- The prescribing of antivirals is recommended in primary care for the treatment of patients with severe illness (influenza/ influenza like illness (ILI)) and the targeted use of antivirals for the treatment of non-severe influenza in patients at high risk of progression to severe disease is recommended following a risk benefit analysis at the clinician's discretion. This applies only during the period in which the Health Protection Surveillance Centre (HPSC) issues an alert that influenza viruses are circulating in the community.
- Ideally, treatment should be initiated early, within 48 hours of symptom onset if oseltamivir is being used and within 48 hours for adults or 36 hours for children if inhaled zanamivir is being used. Prescribers should not delay commencement of treatment while awaiting confirmatory diagnostic test results or if specimens are not obtained.
- Regional Departments of Public Health should be notified of all local influenza/ acute respiratory outbreaks.
- Non severe influenza: Uncomplicated, non-severe, influenza illness is characterised by symptoms including a sudden onset of cough, headache, muscle and joint pain, severe malaise, sore throat and rhinorrhoea, with or without fever. Most people recover from the fever and other symptoms within a week, without requiring medical attention. Defined as absence of any criteria of severe disease
- Severe influenza: Influenza virus can also cause severe illness (such as sepsis, septic shock, severe pneumonia, acute respiratory distress syndrome [ARDS], multi-organ failure, exacerbation of chronic medical conditions) or death. These conditions would normally require hospitalisation and in some severe and critical cases the provision of oxygen, mechanical ventilation (invasive or non-invasive) and/ or vasopressor therapy.
- Previously healthy people (excluding pregnant women) No antiviral treatment. Symptomatic treatment only.
- Pregnancy: Antivirals are recommended for pregnant women or women up to two weeks post partum (including following pregnancy loss) with suspected or confirmed severe influenza due to the adverse clinical outcomes that have been observed for influenza in this group. Oseltamivir remains the first line option for the vast majority of pregnant women with influenza, including during seasons that are dominated by influenza A (H1N1)
- Patients with non-severe influenza and at high risk of progression to severe disease: Oseltamivir oral can be considered for an individual patient following a risk benefit analysis at the clinician's discretion. See below for defined risk groups.
- Patients with severe influenza: All patients with severe influenza should receive treatment, usually in hospital. First-line treatment is oral oseltamivir.
- The risk of resistance is highest in people who are severely immunocompromised. The selection of first line drugs in severely immunocompromised individuals should take into account the influenza A subtype causing infection or, if not yet known, the dominant influenza virus type/ subtype that is circulating during the influenza season. The dominant circulating influenza virus type/ subtype is reported by the HPSC in Integrated Respiratory Virus bulletins during the winter period, available on Integrated Reports - Health Protection Surveillance Centre.
- Expert advisory group recommends seeking expert advice if considering switch to zanamivir in immunocompromised patients.
- Duration of treatment is usually 5 days (10 days for oseltamivir in immunocompromised adults and adolescents)
- Patients who remain unwell after 5 days antiviral treatment need careful clinical assessment. They may have a secondary bacterial infection, or be infected with an antiviral-resistant influenza strain. Specialist consultation is advised especially in immunocompromised or multi-morbidity. There is no evidence that prolonged courses ( > 5 days) of antiviral treatment improve outcome in non-immunocompromised patients.
Treatment
For further information on the treatment of severely immunocompromised patients consult the Antiviral Treatment and Prophylaxis Guidance.
Available products
Oseltamivir
- Oseltamivir capsules (30mg, 45mg and 75mg), oseltamivir powder for oral suspension 6mg/ml.
- Oseltamivir oral suspension should be used for children and adults with swallowing difficulties.
- The SmPC contains further information on extemporaneous formulation of a suspension from the capsules if oral suspension is not available.
- Product information for oseltamivir is available on the HPRA website
- Dose reductions required in renal impairment.(if eGFR <60ml/min/1.73m2 or calculated CrCl <60ml/min).
- Refer to Antiviral Treatment and Prophylaxis Guidance for further information on dosing in haemo-dialysis, peritoneal dialysis and haemo(dia)filtration.
Zanamivir
- Zanamivir powder for inhalation 5mg per dose. It should be noted that zanamivir inhaler is authorised for use in the EU but not marketed in Ireland; zanamivir inhaler is only available as an unlicensed product in Ireland.
- Product information is available on the HPRA website.
- Zanamivir inhaled, warning not to be nebulised
Chemoprophylaxis
Chemoprophylaxis (oseltamivir oral/ zanamivir inhaled) may be considered for asymptomatic persons at extremely high risk for hospitalisation (see below for defined risk groups) if they develop seasonal influenza who have had recent close contact with a person with influenza or influenza like illness (ILI) in the same household or residential setting when influenza viruses are circulating in the community
- Chemoprophylaxis may be considered if the contact is not adequately protected by vaccination OR where the person has been exposed in the context of a local outbreak, regardless of vaccination status.
- Chemoprophylaxis should be commenced within 48 hours of the most recent exposure for oseltamivir and within 36 hours for inhaled zanamivir and is administered for 10 days after the most recent known exposure to a close contact known to have influenza.
- Influenza vaccination and infection prevention and control practices are of utmost importance in the prevention of influenza and are universally preferred over the administration of chemoprophylaxis
For more information consult the Antiviral Treatment and Prophylaxis Guidance.
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Defined Risk Groups for Antivirals
WHO Classification
Patients at higher risk of hospitalisation include those with at least one major risk factor;
Additional risk factors include:
- malignancy
- pregnancy
- diabetes.
Patients at extremely high risk of hospitalisation are defined as:
- Age 85 years or more; or
- Any age + multiple major risk factors
For more information consult:
Residential Care Facilities
Patient Information
Safe Prescribing
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Reviewed December 2024
