Influenza: common questions answered

Influenza, commonly called flu, is an acute viral infection that spreads easily from person to person in any age group. The northern hemisphere’s influenza season usually peaks from December to February, although cases can occur as early as October and as late as May. An epidemic occurs every year, so WHO/Europe and partners such as the European Centre for Disease Prevention and Control (ECDC) work with Member States to conduct surveillance to better understand influenza in the WHO European Region.

Studies of the fatalities and hospitalizations during previous influenza seasons show that certain groups have a higher risk of developing serious complications as a result of influenza. These include older people, pregnant women and people with underlying health conditions such as asthma. Health care workers are at greater risk of exposure to influenza, and can pass it to patients. Most Member States in the WHO European Region prioritize immunization among these groups, but everyone can benefit from seasonal influenza vaccination.

Why should pregnant women be vaccinated, and is it safe?

Pregnancy causes temporary changes to the immune system, heart and lungs that make pregnant women more prone to severe illness when they have influenza. Pregnant women with influenza are more likely to be hospitalized and even die, and they may also face problems that include premature birth and restricted growth of their fetuses.

Seasonal influenza vaccination is safe at all stages of pregnancy. Millions of doses of vaccine have been given to pregnant women all over the world for many years. Once a pregnant woman has been vaccinated, she passes immunity to the fetus, providing protection for the first six months of life.

I don’t catch influenza; why should I bother to be vaccinated?

People with influenza can have a very mild illness or not become ill at all. Nevertheless, they can still spread the disease to others. People who have regular contact with anyone in a risk group – babies too young to be vaccinated or people with suppressed immunity such as those undergoing chemotherapy – may want to consider being vaccinated to protect them.

I was vaccinated and I got sick; did the vaccine cause that?

The vaccine used in seasonal influenza injections cannot give you influenza; it does not contain live influenza virus.

Why should health care workers be vaccinated?

Health care workers are at greater risk of exposure to influenza than the general population. They can pass the disease to their patients, who may be especially vulnerable to complications. Health care workers and their patients deserve to be protected as much as possible by immunization. Good levels of immunity mean fewer sick days and staff shortages.

I was vaccinated against influenza last year; do I need to be vaccinated again this year?

Influenza vaccination is needed every year, because people’s levels of protective antibodies have been shown to decrease over the course of a year. In addition, the influenza virus can change over time, so an influenza vaccination given during one year may not provide protection in another. WHO therefore evaluates the vaccine before each influenza season and recommends to vaccine manufacturers which influenza strains to include in the vaccine for the next season. These recommendations are based on data on which strains have been circulating recently.

Besides being vaccinated, how can I avoid infecting other people?

  • Watch out for the symptoms of influenza; you can be infectious 1 day before you show symptoms and for 5–7 days afterwards.
  • Basic hygiene can stop influenza spreading. Use a tissue if you sneeze or cough, and throw it away afterwards. Wash your hands regularly with soap and water.
  • Stay at home and avoid contact with other people if you are ill.

What are the symptoms, and what should I do if I have influenza?

  • Symptoms include fever, chills, coughs, headaches, muscle aches and tiredness. Children may also vomit and have diarrhoea.
  • If you think you have influenza, stay at home and rest, drink plenty of water and use over-the-counter medicines to treat fever and other symptoms.
  • Do not take antibiotics to treat influenza, which is caused by a virus. Antibiotics kill bacteria, not viruses.
  • If you have influenza and are pregnant or have a chronic health condition such as asthma, call your doctor, who may recommend that you take antiviral medication.