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Factsheet for the general public

In Europe influenza occurs in regular winter epidemics, though the intensity of infection varies from year to year. Even though for most people an influenza virus infection is just an unpleasant experience, the disease has other important impact on European society: Firstly, some people develop a more serious illness that kills them prematurely. It is estimated by ECDC that up to 40,000 people die each year from influenza in the European Union (EU). Secondly, there are significant costs to the health services of Europe in caring for those sick from influenza and thirdly there are significant economic impacts deriving from the large numbers of mild to moderate cases which result in time off work and the consequent losses to production.
Specific population groups are more at risk of becoming seriously affected by influenza, these are the ‘high risk groups’ older people (usually those over age 65 years though that age differs a little from country to country in Europe) and those with chronic ill-health. For these high-risk groups, yearly vaccination in the autumn is recommended in most EU countries, in an approach known as ‘selective vaccination’ which reduce their risks of complications, severe disease and death.


Human influenza viruses reproduce and transmit easily from one human to another. They spread predominately by droplets when people cough and sneeze and indirect contact from respiratory secretions getting onto hands, tissues etc. Influenza symptoms usually comprise the following, though not every sufferer will necessarily
show all symptoms:
  • a high temperature
  • runny nose,
  • sore throat,
  • dry cough,
  • a general feeling of ill-health,
  • headache
  • aching muscles.

The more serious symptoms typically last for only a few days, but the sore throat and runny nose may last longer. Some people can be infected with the influenza virus but have no symptoms, or only very mild symptoms. Usually, though, influenza makes people quite ill and they take a week or so to fully recover. However, it should be realised that many other viruses, and some bacteria, can cause symptoms similar to influenza – so not everyone with “flu like symptoms” actually has “flu”. Unfortunately in some countries it is traditional to call even mild illnesses ‘flu’ , ‘grippe’ or a ‘touch of flu’. This is not to be encouraged as it results in people thinking influenza is less significant than it really is.

Once you have been infected with a particular influenza virus you usually become immune to it. You can also acquire immunity by being vaccinated. However, the virus circulating changes from year to year so immunity tends to last only for one season. That is why people who are recommended to be immunised need to receive their injection every autumn.
The incubation time for influenza (the number of days from when you are exposed to developing symptoms) ranges from 1 to 5 days, but the average is 2 days. Influenza viruses are generally divided into three types: A, B and C, of which the two first are of more concern as they cause the most serious illnesses. In some cases the disease becomes more severe due to more extensive spread of the virus in the body or a second, usually bacterial, infection. This most commonly results in severe lung infections (pneumonias) which can be fatal.


Although complications from flu can occur in anyone, they are far more common among the high-risk groups:
  • The elderly
  • People with chronic medical conditions, such as heart disease, and people whose immune systems are weak

There are different approaches in the countries regarding the groups to be vaccinated. As for the elderly, the specific age for people to be classified in this group may vary from one country to another. A majority of countries recommend vaccination for people aged 65 and over, however some recommend it for people aged 60 and over or even 50 and over. In any case, the World Health Assembly (the supreme decision-making body of WHO) which includes all EU/EEA countries, supported a proposal in 2003 that there should be targets for uptake in the elderly of 50% by 2005 and 75% by 2010. Currently most EU/EEA countries fall short of this standard.

Furthermore, many countries especially emphasise the importance of annual immunisation of people living in residential care for the elderly and disabled. The majority of countries in Europe recommend that all health care staff should be immunised against influenza, so that staff more likely to be exposed through their work are protected, as well as the patients they are dealing with. Few EU countries recommend immunising children or offering vaccines to pregnant women. An expert panel convened by ECDC considered there was as yet insufficient evidence on the burden of infection in children to take any view for or against immunisation.



Because the strains of popular flu viruses may differ from year to year and because the vaccines protection fades yearly vaccination is recommended. Vaccines are made in advance of the flu season based upon the viruses from the previous year’s epidemics. However, a virus causing a particular year’s epidemic can also occasionally be somewhat different from last years, in which case the vaccine may be less effective and need changing the next year.
Estimates of vaccine efficacy and effectiveness – the extent to which vaccine protects in optimal circumstances (efficacy) and in practice (effectiveness) – vary according to the match between vaccine and the circulating viral strain, by age group and clinical category. However the vaccine does reduce the risk of ill-health and saves lives. ECDC strongly supports the recommendations of Member States and WHO that the vaccine should be used by the high risk groups.
This factsheet offers basic information on what influenza is and how vaccines can help people in high-risks groups to reduce their chances of becoming seriously ill. It is intended for information purposes only, not as medical advice. If you need advice on your own personal health then you should consult a healthcare provider in your country.
© European Centre for Disease Prevention and Control (ECDC) 2005 - 2016