Seasonal Influenza

Comments fluvirusimage

  • When influenza A or B is circulating in the community, antiviral therapy should be considered for influenza-like illness in patients who are very ill or who are in recognised risk groups for severe influenza. Information will be issued to GPs when influenza rates increase and antivirals are recommended
  • For otherwise healthy adults antivirals are not generally recommended.
  • More detailed 2016 information on treatment of or chemoprophylaxis for seasonal influenza, including in pregnant or immunosuppressed patients is available in short summary document by clicking here.
  • The editorial group recommend that these HPSC guidelines are consulted prior to making the final prescribing decision.


Key points from 2016-2017 HPSC Antiviral Treatment of Influenza Guidelines are as follows:
  1. Previously healthy people (excluding pregnant women ) do not need antiviral treatment unless the clinician feels the patient is very ill or is at serious risk of developing complications from influenza. Symptomatic treatment is the preferred option.
  2. At risk population: prescribe oseltamivir (PO). Do not wait for laboratory confirmation. Treatment should be started as soon as possible, ideally within 48 hours of onset. There is evidence that treatment may reduce the risk of severe illness up to five days after onset. Severely immunosuppressed patients: prescribe oseltamivir (PO) Rapid emergence of oseltamivir resistance on treatment has been described in these patients and they should be monitored closely. Resistance to oseltamivir has been described in infections from influenza A (H1N1) pdm09 subtype but not in those from influenza A (H3) to date (source: NVRL). Clinicians may consider the use of zanamivir (inhaler) as first line therapy in immunosuppressed patients with suspected or confirmed influenza A (H1N1) pdm09 based on clinical judgement. In immunosuppressed patients, if no clinical improvement is seen within 5 days, patients should be tested for antiviral resistance.
  3. Suspected or confirmed oseltamivir resistant influenza in a patient who requires treatment: Zanamivir (inhaler) 10 mg (2 inhalations) bd. Treatment should be started as soon as possible and ideally within 36 hours of symptom onset.

The official detailed prescribing information recommended by the HPRA including the patient information leaflet for all formulations can be found here Tamiflu SmPCRelenza SmPC

Defined Risk Groups for Antivirals

  1. Age 65 years and over
  2. Pregnancy (including up to two weeks post partum)
  3. Children aged <2 years of age
  4. Chronic respiratory disease including those on medication for asthma
  5. Chronic heart, kidney, liver or neurological disease
  6. Diabetes mellitus
  7. Haemoglobinopathies
  8. Immunosuppression (whether due to treatment or disease e.g. HIV)
  9. Morbid obesity (BMI ≥40)
  10. Those with any condition that can compromise respiratory function (e.g. cognitive dysfunction, spinal cord injury, seizure, or other neuromuscular disorder), especially those attending special schools/day centres
  11. Down Syndrome
  12. Children with moderate to severe neurodevelopmental disorders such as cerebral palsy and intellectual disability
  13. Residents of nursing homes or other residential care facilities

back to top


See guidance on dosing in children for quick reference dosage/weight guide

Table 1: Antiviral Treatment dosages and schedules for treatment
0-12 months6 1-12 years: Dose according to weight below: Adults
≤ 15kg >15-23kg >23-40kg >40kg
Oseltamivir PO
(treatment course: 5 days)
dose bd
30mg bd 45mg
75mg bd 75mg bd
Zanamivir inhaled (treatment course: 5 days) Not licensed for children <5 years old.
For children aged ≥5 years, Dose:10mg (two 5mg inhalations) bd
(two 5mg inhalations) bd

Table 2: Antiviral dosage and schedules for chemoprophylaxis
Prophylaxis 0->3
1-12 years: Dose according to weight below Adults
(13 years and over)
≤ 15kg >15-23kg >23-40kg >40kg
Oseltamivir PO
(Prophylaxis course: 10 days)
See footnote 10 below 3mg/kg
30mg od 45mg od 60mg od 75mg od 75mg od
Zanamivir INH (Prophylaxis course: 10 days) Not licensed for children <5 years old.
For children aged ≥5 years, 10mg (2 inhalations) od

10mg (2 inhalations) od

Footnote 10: If a child is younger than 3 months old, use of oseltamivir for chemoprophylaxis is not recommended unless situation is judged critical due to limited data in this age group

back to top

The full HPSC Antiviral Treatment of Influenza Guidelines are available here.*Advice of the influenza subgroup of the scientific advisory committee, HPSC on the use of antivirals in pregnancy, for patients with influenza

All pregnant women with influenza like illness should seek medical advice.
  • Antivirals have been recommended for pregnant women 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)
  • For pregnant women who meet additional criteria for requiring zanamivir first line, further assessment (i.e. rapid diagnostics) and antiviral treatment should be discussed with a local infection specialist.
  • Oseltamivir is generally well tolerated in patients with influenza, but side effects can occur. There are no data suggesting tolerability differs between pregnant and non-pregnant adults
  • Recent studies suggest there is no evidence of harm in pregnant women treated with oseltamivir or zanamivir
  • Chemoprophylaxis is not routinely recommended for pregnant women. However, clinical judgement may be exercised in individual cases if the benefit outweighs the risk.

Patient Information

The HSE Health A-Z website provides patient information on many hundreds of conditions and treatments.

We recommend patients use the website developed by HSE/ICGP/IPU partnership for tips on how to get better from common infections without using antibiotics, what you can do for yourself or a loved one and when to seek help.

 Reviewed June 2017