Influenza Prevention and Treatment in Primary Care

NICE interactive flow chart - influenza  https://pathways.nice.org.uk/pathways/influenza

Prevention
Annual vaccination is essential for all those at risk of influenza (see DoH ‘Green Book’).
Encourage good hand and respiratory hygiene to limit the spread of ‘flu.
Consider antivirals for post-exposure prophylaxis in at risk groups or during localized outbreaks in care homes.

The antiviral agents’ oseltamivir and zanamivir are licensed for the treatment and post-exposure prophylaxis of influenza.

1. Treatment

Antivirals are recommended for the treatment of seasonal influenza in adults and children if the following circumstances apply:

• National surveillance schemes indicate that influenza virus A or B is circulating in the community (GP in receipt of the Chief Medical Officer (CMO)/Chief Pharmaceutical Officer (CPhO) letter)

OR

• during localized outbreaks of suspected or confirmed influenza in a long-term care home at any time (i.e. including outside the CMO defined  ‘influenza season’) if there is a high level of certainty that the causative agent in the localized outbreak is influenza (usually based on virological evidence of influenza infection in the initial case). Contact local PHE team and community IPC team.

AND

• The person has uncomplicated ‘flu but is in an 'at-risk' group for developing complicated influenza (see below), or the person has complicated ‘flu regardless of risk group

AND

• the person presents with an influenza-like illness or has confirmed influenza and can start treatment within 48  hours (or within 36 hours for zanamivir treatment) of the onset of symptoms

For uncomplicated influenza in otherwise healthy adults, (excluding pregnant women), anti-virals are not recommended.
Consider prescribing antiviral treatment if the person is not in an 'at risk' group, but it is felt that they are at a risk of developing serious complications.
Do not wait for laboratory confirmation before starting treatment.
There is a lack of evidence to show that antiviral drugs are effective at preventing influenza if treatment is started after the recommended times and the HPA advises that treatment after these times is an off-label use and clinical judgement should be exercised. Use of antivirals up to 5 days after symptom onset probably has benefit.

For further information in regards to providing antiviral prophylaxis to residents within a care home where there is indication of an outbreak, please see the following link.

 Preferred Option

Alternative Option

Notes

Adult patients (and those aged 13 years or over) with complicated ‘flu or patients with uncomplicated flu who are ’at  risk’ of complications, including pregnant women:
Oseltamivir 75 mg oral capsule BD for 5 days
(10 days for severely immunosuppressed patients)
(use 30 mg twice daily if eGFR 30–60 mL/minute/1.73 m2; 30 mg once daily if eGFR 10-30 mL/minute/1.73 m2).
For children’s doses see BNFc.
Prescriptions should be endorsed ‘SLS’.
Consider using inhaled zanamivir as alternative where oseltamivir is indicated in patient with impaired oral absorption.
If an immunosuppressed patient treated with oseltamivir does not improve, discuss with virology re: resistance testing and switch to inhaled zanamivir.

If subtype testing in an immunosuppressed patient treated with oseltamivir confirms a strain with potential oseltamivir resistance e.g. A (H1N1), switch to inhaled zanamivir.

For treatment of influenza if known resistance to oseltamivir
or
if severely immunocompromised and the dominant circulating strain has a higher risk of oseltamivir resistance eg A (H1N1)pdm09
or
oseltamivir is indicated but unlikely to be effective due to impaired oral absorption:
Zanamivir 10 mg (2 inhalations by diskhaler) BD for 5 days (and seek specialist advise). Not licensed in children less than 5 years.
Prescriptions should be endorsed ‘SLS’.

If zanamivir is indicated but patient is unable to use the diskhaler, or is <5yo, use oseltamivir oral capsule and assess response.

If known/suspected oseltamivir resistance, consider IV zanamivir (seek specialist advice).

At risk groups for complicated influenza:  pregnant (including up to 2 weeks post-partum), 65 years or over, chronic respiratory disease (including COPD and asthma), significant cardiovascular disease (not hypertension), severely immunocompromised (see Green book), diabetes mellitus, chronic neurological, renal or liver disease, persons with BMI ≥ 40, children <6 months old.

Complicated ‘flu is ‘flu requiring hospital admission and/or symptoms and signs of lower respiratory tract infection, CNS involvement and/or significant exacerbation of an underlying medical condition.

Swallowing difficulties: Children over one years and adults with swallowing difficulties, and those receiving nasogastric oseltamivir, should use capsules which can be opened and mixed into a sugary liquid to disguise the taste. The powder for suspension should be reserved for children under one years old to preserve the stocks.

For further details of prescribing anti-virals in hepatic and renal dysfunction see PHE Guidance.

2. Use of antiviral agents for the Post Exposure Prophylaxis (PEP) of seasonal influenza

Antivirals are recommended for the PEP of influenza in adults and children if the following circumstances apply:

• National surveillance schemes indicate that influenza virus A or B is circulating in the community (GP in receipt of the Chief Medical Officer (CMO)/Chief Pharmaceutical Officer (CPhO) letter)

OR

• during localized outbreaks of suspected/confirmed influenza in a long-term care home at any time (i.e. including outside the CMO defined  ‘influenza season’) if there is a high level of certainty that the causative agent in the localized outbreak is influenza (usually based on virological evidence of influenza infection in the initial case). Contact local PHE and community IPC teams.

AND

• The person is in an 'at-risk' group for developing complicated influenza.

AND

• the person has been in close contact with a person (in the same household or residential setting) who has had recent symptoms of suspected or confirmed influenza and is able to start treatment within 48 hours of this contact (for oseltamivir) or 36 hours (for zanamivir).

AND

• and has not been effectively protected by vaccination against influenza (i.e. they have not been immunized in the present influenza season, or the Health Protection Agency has indicated that the vaccine is not well matched to the present circulating strain, and those for whom vaccination is contraindicated, or in whom it has yet to take effect i.e. <14 days between vaccination and date of contact with influenza).

Note prophylaxis may be used to control outbreaks of influenza in at-risk people living in long-term residential or nursing homes, whether or not they are vaccinated.

Antiviral prophylaxis started after 48 hours (for oseltamivir) or 36 hours (for zanamivir) is an off-label use and should be done on specialist advice only. The British National Formulary states that in people with severe influenza or people who are immunocompromised, antivirals may still be effective after these times if viral shedding continues.

Preferred Option

Alternative Option

Notes

Adult patients (and children over 13 years of age) at risk of complicated ‘flu, including pregnant women (see dosing below for the severely immunosuppressed and those < 13yo)
Oseltamivir 75mg oral capsule OD for 10 days.
(use 30mg OD if eGFR 30-60ml/minute/1.73m²; 30mg every 48 hours if eGFR 10-30ml/minute/1.73m²)

If the circulating strain in index case is higher risk of oseltamivir resistance e.g. A (H1N1)pdm09 and in ‘at risk group’
Oseltamivir oral capsule 75mg OD for 10 days.

If exposed to suspected or confirmed oseltamivir resistant influenza and in ‘at risk’ group
Zanamivir INH 10mg OD for 10 days.

Severely immunosuppressed patients (excluding children <5 years old). 
For adults and children above 13, Oseltamivir 75mg oral capsule OD dose for 10 days.
See BNFc for children doses (5-13years old) based on body weight.

Severely immunosuppressed >/=5 years old where the circulating strain in index case is higher risk of oseltamivir resistance e.g. A (H1N1)pdm09
Zanamivir INH 10mg OD for 10 days
2nd line: Oseltamivir oral capsule OD dose for 10 days. See BNF or BNFc for dosing.

If exposed to suspected or confirmed oseltamivir resistant influenza and severely immunosuppressed (excluding <5years old)
Zanamivir INH 10mg OD for 10 days.

If unable to administer Zanamivir INH to a severely immunosuppressed patient 5years or over exposed to confirmed/suspected oseltamivir resistant influenza, monitor closely and start treatment promptly if influenza-like symptoms develop

Children <5years old in at risk groups including those severely immunocompromised.
Oseltamivir oral capsule OD dose for 10 days. See BNFc for dosing as based on body weight.

Children <5years old including those severely immunocompromised where the circulating strain in index case is higher risk of oseltamivir resistance e.g. A (H1N1)pdm09
Oseltamivir oral capsule OD dose for 10 days. See BNFc for dosing as based on body weight.

For children less than 5 years exposed to confirmed/suspected oseltamivir resistant influenza monitor closely and start treatment promptly if influenza-like symptoms develop

NICE prophylaxis guideline
NICE treatment guideline
PHE