MRCGP exam update: Efficacy of the flu vaccine

Current situation  

During the winter there is usually an outbreak of influenza, caused by influenza A or B virus, which results in a huge increased workload for primary care teams and hospitals.   

Even when the incidence is low, it has been estimated that between 3,000 and 4,000 deaths in the UK each year are from influenza-related causes. 

Diagnostic ignorance poses problems with applying preventive and treatment interventions, as they are specific against influenza A and B viruses.  

Each year, the WHO recommends the strains to include in vaccinations for the next season.  

What is the evidence?  

There is much evidence to support the efficacy of vaccination; it reduces mortality and morbidity in high-risk groups.     

However, doubts about the influenza vaccine have been raised recently. A review of 64 studies on the efficacy of the influenza vaccine has found no evidence that vaccines were effective in protecting older people against influenza-like illnesses, influenza or pneumonia (Lancet 2005; 366: 1,165).      

Evidence is still insufficient to recommend universal vaccination against influenza in healthy adults. A review found that vaccinating healthy adults not at risk of complications reduced their chances of developing flu-like illness by only a quarter; the number of lost working days were reduced by less than half a day (Cochrane Database of Syst Rev 2006; 3: CD004879).  

Adults with diabetes, like other high-risk groups, benefit from receiving the influenza vaccine each year regardless of age (Diabetes Care 2006; 29: 1,771).  

A recent systematic review has shown that the neuraminidase inhibitors have low effectiveness and should not be used in seasonal influenza control. It is suggested that they only be used in a serious epidemic or pandemic alongside other public-health measures (Lancet 2006; 367: 303).   

Implications for practice  

The possible emergence of resistance further limits the routine use of neuraminidase inhibitors.  

Although amantadine is licensed for prophylaxis and treatment of influenza A, it is no longer recommended (see NICE guidance).  

Available guidelines  

NICE has produced recommendations regarding the use of the neuraminidase inhibitors for the prophylaxis and treatment of influenza. They are only recommended for at-risk patients. This guidance is overdue for review.  

Community-based virological surveillance schemes such as those run by the Health Protection Agency should be used to indicate when influenza is circulating in the community.  

Useful websites — NICE — Health Protection Agency  

Dr Louise Newson is a GP in the West Midlands and author of ‘Hot Topics for MRCGP and General Practitioners’, Pas Test 2006  

Key points  

Influenza still leads to many deaths in the UK.  

Effectiveness of the vaccine in the community is questionable.  

The use of amantadine and rimantadine should be discouraged.  

The cost-effectiveness of antivirals is still unproven. 

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