Seasonal influenza FAQ

What is influenza?

Seasonal influenza is a contagious respiratory disease caused by an influenza virus. It is not the same as a common cold. Influenza is characterized by a sudden onset of fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), a sore throat and a runny nose. The cough can be severe and can last 2 or more weeks. Influenza cannot be treated with antibiotics. Severe cases of influenza may be treated by antivirals under the supervision of a doctor. The best protection against influenza is vaccination.

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Is influenza really that serious?

Most people recover from fever and other symptoms within a week without requiring medical attention. However, influenza can cause severe disease and death, especially in people over 65, young children, pregnant women and people with long-term health conditions. Every year, people in these at-risk groups die from influenza. Worldwide, up to 650 000 people die of respiratory diseases linked to seasonal influenza each year, and up to 72 000 of these deaths are in the WHO European Region.

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Who is at higher risk of health complications from influenza?

When influenza starts to spread every winter, WHO strongly recommends that certain groups be vaccinated against the disease. These include:

  • pregnant women;
  • individuals with chronic heart or lung diseases, metabolic or renal disease, chronic liver disease, chronic neurological conditions or immunodeficiencies;
  • people over a nationally defined age limit, irrespective of other risk factors (typically people over 65);
  • residents of long-term care facilities for older people and the disabled;
  • children aged 6–59 months; and
  • health-care workers, including those who work in facilities that care for older people or people with disabilities.

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How can I protect myself against influenza?

The best way to prevent or minimize severe disease from influenza is timely vaccination. In addition to vaccination, personal protective measures should always be practiced. These include:

  • regular handwashing and proper drying of hands;
  • good respiratory hygiene (covering the mouth and nose when coughing or sneezing, and using tissues and disposing of them correctly);
  • early self-isolation when feeling unwell or feverish, or when experiencing other symptoms of influenza;
  • avoidance of close contact with sick people; and
  • avoidance of touching the eyes, nose or mouth.

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When should people consult a doctor if they have influenza?

Influenza is always unpleasant regardless of the influenza virus type, but it is usually mild and most people recover quickly. People with symptoms such as coughing, sneezing, sore throat, headache and a slight temperature should rest at home; they can visit their local pharmacy for advice or use painkillers and decongestants. People with severe or unusual symptoms and those at increased risk of severe disease (children under 5, people over 65, pregnant women and people with a pre-existing medical condition) should contact their physician to determine whether antiviral or other treatment is needed.

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When should a person get vaccinated and how often?

It is best to get vaccinated before the influenza season starts. Influenza vaccination campaigns usually take place around October, soon after the vaccine becomes available. After receiving the vaccine, it takes 2 weeks to develop protective antibodies against influenza. However, it is never too late to be vaccinated if influenza is still circulating. Vaccination increases the chances of being protected from infection and may lessen severe consequences of the disease.

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Why do people need to be vaccinated every winter?

It is important to be vaccinated every year. This is partly because influenza viruses constantly change, meaning different strains can circulate each year, and partly because immunity from an influenza vaccination decreases over time. Seasonal influenza vaccines are updated each year to provide the highest possible protection by matching the circulating viruses.

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Why is influenza vaccination not always promoted to healthy working-age adults?

WHO recommends prioritizing vaccination for older individuals, young children, pregnant women and people with underlying health conditions because these are the groups most likely to suffer serious complications from influenza. However, anyone can catch influenza, and healthy working-age adults can also be vaccinated. In the case of health-care workers, they need to be vaccinated to protect themselves and to reduce their risk of infecting vulnerable patients with the virus.

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Can an influenza vaccine cause influenza?

No, influenza vaccines are safe and do not cause influenza. You might experience a reaction to the vaccination, but this reaction will not be influenza and will be milder than influenza symptoms. Even if you have been vaccinated, it is possible to get influenza. This is because the year’s vaccine is designed to protect against the season’s expected types of influenza, but not against every type of influenza. Furthermore, your individual immunity might make you more susceptible to a specific type of influenza. Nonetheless, vaccination is still recommended – even if you do get influenza, the symptoms will be milder and therefore less dangerous.

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Are seasonal influenza vaccines safe?

Seasonal influenza vaccines have been in use for more than 50 years, have been administered to millions of people and have a good safety record. Every year, national medicines regulatory authorities carefully examine each influenza vaccine before it is licensed. Systems are in place to monitor and investigate any reports of adverse events following influenza immunization.

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Which types of influenza does the vaccine protect against?

Type A and type B influenza viruses infect people every year. Trivalent influenza vaccines are currently the most commonly used vaccines in Europe. “Trivalent” means that the vaccine protects against 3 influenza strains. WHO decides in February each year which influenza strains should be covered by the vaccine for the northern hemisphere in the coming season – usually 2 type A viruses and 1 type B virus. This decision is based on the best available evidence as to which viruses are likely to circulate. In recent years, quadrivalent influenza vaccines protecting against 2 type A and 2 type B viruses have also been marketed.

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Why are quadrivalent vaccines available in some countries but not others?

So far, trivalent vaccines have been the most widely used vaccines in Europe. Trivalent vaccines protect against 3 influenza viruses – usually 2 type A viruses and 1 type B virus. Discussions on the advantages of shifting to quadrivalent vaccines, which protect against 2 type A and 2 type B viruses, are ongoing. Quadrivalent vaccines are more expensive, but studies in some countries have shown that they may be cost-effective if overall costs for the health-care sector are taken into account. However, the economic background varies from country to country.

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How is the formulation of the vaccine decided?

WHO makes a recommendation of what should go into the vaccine each year to target the viruses that are expected to circulate in the coming season. The recommendation is based on information from the WHO Global Influenza Surveillance and Response System, the body responsible for monitoring the types of viruses circulating and rapidly identifying new strains. WHO also takes into consideration vaccine effectiveness in previous and current influenza seasons. For more information on how WHO selects virus strains for inclusion in the influenza vaccines for the northern and southern hemisphere, see: http://www.who.int/influenza/vaccines/virus/en/

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How is the vaccine made?

Influenza vaccines are most commonly made using an egg-based manufacturing process. This process has been used for more than 70 years. The egg-based process produces both the inactivated (killed virus) vaccine, which is the most common version and is given by injection, and the live attenuated (weakened virus) vaccine, which is given as a nasal spray.

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How long does it take to make the vaccine each year?

From the time WHO publishes the recommended composition of influenza vaccines for use in the upcoming season, it takes 6 months to produce the new vaccine.

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How does WHO collect data about influenza viruses?

The WHO global influenza surveillance network monitors circulating influenza viruses and rapidly identifies new viruses. National influenza laboratories and other public health organizations provide this information.

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The influenza virus A(H1N1) is circulating in the WHO European Region – has the 2009 pandemic virus come back?

The A(H1N1) virus, which caused the influenza pandemic in 2009, has continued to circulate in people in Europe and elsewhere and is now a seasonal human influenza virus. In 2009, the global population had little immunity to A(H1N1) because it was new. It caused a global epidemic and was responsible for an estimated 100 000 to 400 000 deaths that year. The A(H1N1) virus now circulates as a seasonal influenza virus. The seasonal influenza vaccine provides protection against A(H1N1). Flu News Europe provides a weekly overview and assessment of influenza activity in the WHO European Region based on surveillance data from the Region’s 53 Member States: http://flunewseurope.org/

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Is the seasonal A(H1N1) virus different from the A(H1N1) virus that emerged during the 2009 pandemic?

The A(H1N1) virus now circulates as a seasonal human influenza virus. It has not changed significantly from the 2009 virus, and there is no evidence that it has become more harmful. Since its emergence in 2009, the A(H1N1) virus has caused rare cases of severe disease in otherwise healthy, young adults, including pregnant women. In contrast, the A(H3N2) virus is more likely to cause severe disease and death in older people. Clinicians must be aware of this so they can administer early treatment with an influenza antiviral drug (oseltamivir) to patients who show severe respiratory symptoms. WHO has prepared advice for European clinicians on managing severe complications of influenza.

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What is swine flu?

The term “swine flu” is no longer used in connection with influenza in humans. In 2009, some influenza A(H1N1) virus infections were referred to as swine flu due to the transmission of the A(H1N1) virus from swine to humans at the start of the 2009 influenza pandemic. Since then, the virus has continued to circulate worldwide as a seasonal human influenza virus and therefore the term swine flu is now misleading.

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How does the influenza virus spread around the world?

Influenza is carried by people from place to place, transmitted from person to person mostly by coughs, sneezes and breathing. In temperate climates of both the northern and southern hemispheres, the influenza season happens in the winter. In the tropics, influenza viruses can infect people all year long. In this age of international travel, people can catch influenza and bring it by plane to their home country even outside of the regular season.

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Is there any pattern in the direction of travel of influenza viruses, for example, from the southern hemisphere to the northern hemisphere, or vice versa?

From year to year, the predominant influenza virus type and subtype causing the outbreak varies. The intensity and impact of the disease, the epidemiologic dynamics (who is affected and when) and the pattern of transmission also vary. Research is being done to better understand these global transmission patterns. However, definitive patterns have not yet been identified. We often see west-to-east and some south-to-north spread of influenza across the countries of the WHO European Region, but this is not consistent.

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What are the key aspects of influenza outbreaks that countries need to share in order to help with forecasting elsewhere?

A variety of information is used in forecasting and predictive modelling of seasonal influenza, including the weekly incidence of disease and mortality; the timing, location and duration of outbreaks; the characteristics of those who become severely ill or die; and the genetic and antigenic properties of circulating influenza viruses. National public health laboratories and surveillance systems routinely collect these data. The good news is that much progress has been made in the last 10 years in the number of countries that regularly share this data with WHO. WHO uses this information to understand the global situation, to select appropriate vaccine strains, and in research activities such as forecasting. In the WHO European Region alone, 49 out of 53 countries routinely share their surveillance data during the influenza season.

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