Flu season is coming - is your practice ready?

Using antiviral therapy for influenza in general practice: The therapy, when and why to prescribe and challenges for clinical workflow

Professor Simon de Lusignan, Medical Director Royal College of General Practitioners Research and Surveillance Centre and Professor of Primary Care & Clinical Informatics – University of Surrey

Antiviral therapy for influenza

There are two antiviral therapies licenced for use in the UK for the treatment and prevention of influenza that are recommended by the National Institute for Health and Care Excellence (NICE):

  • Osteltamivir (Tamiflu) and
  • Zanmivir (Relenza)

They act by slowing the replication of the influenza virus, and are effective against both influenza A and B.  Optimal clinical benefit occurs when antiviral treatment is started within 48 hours of onset of symptoms (36 hours for Relenza and in children), though they may still have some benefit in severe cases and in the immunocompromised after this time. 

Vaccination remains the best way to prevent influenza for target groups. However, it does not rule out infection in someone who presents with signs and symptoms of influenza.

When to prescribe for treatment

Antivirals have been recommended for the treatment and prophylaxis of influenza.

Active treatment of likely influenza
These preparations are recommended for prescription to treat flu when all of the following circumstances apply:

  • The patient has an influenza-like-illness (ILI) at a time when influenza is circulating in the community as declared by the CMO based on PHE influenza surveillance. The RCGP Research and Surveillance Centre (RSC) weekly reports are a good source of information about circulating influenza. A new report is posted each Thursday afternoon, as a downloadable pdf. The winter focus of the report is on influenza-like illness.


  • The patient is in a high risk group (over 65 years, has an underlying risk factor e.g. diabetes, heart, chronic lung, liver or kidney disease or is immunosuppressed).


  • They are able to start treatment soon after the onset of symptoms (it is not necessary to wait for laboratory confirmation).

Prophylaxis against influenza
Where there is circulating flu within a household, nursing or residential home then antiviral therapy can be prescribed for prophylactic treatment for those in a high risk group who are exposed to the virus. The Chief Medical Officer (CMO) makes an announcement each year about circulating flu.

Special arrangements will be made for pandemics or emerging pandemics.  It is thought that antivirals combined with social distancing measures could eliminate a nascent pandemic. 

Why prescribe

The benefit-risk balance of prescription of antivirals was called into question by a recent Cochrane review.  It reported reduction in symptoms, and limited benefit against complications, such as pneumonia (Tamiflu) and bronchitis (Zanmivir). It also pointed out that there was increased nausea and vomiting with Tamiflu. However, international expert consensus remains that benefits outweigh risks. European and North American public health bodies continue to recommend the use of antivirals. This is particularly so in years like 2014-15 where there was some antigenic drift in the prevalent influenza strain, making vaccination less effective. 
Prescription of these preparations continues to be recommended by NICE because they shorten the duration of illness and can lessen complications in people with chronic disease. The NICE assessment of the evidence-base around these drugs suggests that they result in a shorter duration of illness (by just under a day) and faster return to normal activity (by around 1½ days), and less antibiotic use. Observational studies and a meta-analysis demonstrate that early treatment with antivirals reduces the risk of severe outcomes.

Useful references

Challenges for clinical workflow

There are challenges as to how to incorporate antiviral prescribing into normal clinical workflow. Below are two possible scenarios, of the many alternatives which present challenges for general practice.

Scenario 1: A residential or nursing home in your practice area has a case of influenza
If influenza is detected in a nursing home your practice looks after, you may wish, or be requested by the local public health team to, prescribe antiviral therapy for all or part of that facility. This needs to be prescribed on individual prescriptions for each patient, and as soon as possible after the onset of symptoms. This would involve going into each of those patient’s notes and prescribing - taking into account any care plans or other directives in those records. The need to do this is likely to occur at a time when practices are busiest. This is a challenge for practices and is apparently a scenario also not included in our GP contract! This is a scenario practices might want to think through and prepare for ahead of the flu season; perhaps working through who in each practice could support the duty GP with this task.

Scenario 2: Presentation of a large number of people to primary care for antiviral
NICE considered it plausible that more people would attend general practice early in viral illnesses if the use of antivirals was widely promoted and this might lead to a spurious rise in the diagnosis of influenza-like illness in primary care.


Notwithstanding the criticism from the Cochrane review, expert consensus and public health body recommendations remain that these drugs are a useful part of the clinical armamentarium. During last winter, as in most flu seasons, there was an excess mortality related to flu particularly in the elderly; possibly made worse by antigenic shift in the flu virus. Whilst challenges remain as to how to practically incorporate the use of antivirals into general practice workflow, we should aspire to use these medications as clinically recommended, remembering of course that flu vaccination rightly remains a more major part of our anti-influenza endeavours. 

UK Public Health support and advice




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