Influenza is caused by a viral infection which mainly affects the nose, throat, bronchi and, in some cases the lungs.
Every year the winter months see a surge in cases of seasonal flu which has a significant impact on public health and health services.
Most people recover within a week or two but vulnerable people – such as the very young, the elderly and those with a serious underlying medical condition – can suffer severe complications. In some cases, infection can lead to pneumonia and death.
The European Centre for Disease Prevention and Control (ECDC) says surveillance and immunisation are crucial to protecting Europeans against seasonal influenza.
Is flu preventable?
Yes. Flu vaccines can protect against influenza.
Annual flu epidemics affect up to 20% of the population every year, leading most developed countries to embark on immunisation ahead of the flu season.
How is seasonal flu vaccine composition decided?
The flu shot is made up of vaccines against the most common viruses in circulation. Experts at the World Health Organisation (WHO) monitor flu disease for any changes in the viruses and then make a recommendation to health authorities across the world on the composition of the vaccine for the forthcoming season.
In 2009 a major change in the virus was observed as a new strain of flu – known as H1N1 – started spreading across continents and lead the WHO to declare the first full-scale influenza pandemic in decades. Specific single vaccines against this form of influenza were produced at that time and the H1N1 strain was later also incorporated into the annual flu shot for the following season.
Two winters, two seasonal flu vaccines
The WHO consults its network of influenza surveillance centres twice a year – once to help decide on the composition of the vaccine for the northern hemisphere, and once to decide on which viruses people need protection against in the southern hemisphere. The seasonal vaccines given north and south of the equator are usually similar but can differ slightly given the pace with which flu viruses can change.
In 2009, the EU recommended countries to ensure that 75% of their elderly population and 75% of people with some specific underlying health problems are vaccinated every year against seasonal flu. However, the majority of EU countries are falling short of these European targets for uptake of the seasonal flu vaccine. WHO, health authorities and academics say flu vaccination is effective, the vaccine has an excellent safety record and warn against complacency.
