About the flu

Influenza is caused by a virus that is found all over the world. There are three types of influenza viruses that are transmitted between humans, type A, B and C. It is type A flu that causes the biggest epidemics. Type C infection usually causes milder cold symptoms. In addition, there are special influenza viruses that affect specific animal species, e.g. bird flu. These only spread to humans in exceptional cases. The flu virus has a great tendency to change properties (mutate). The infection is airborne and every winter the flu comes to Sweden. It is usually most intense in January and February.


For most people, the flu means that you become feverish (often high fever 39-40 degrees), runny nose, have a dry cough, headache and joint pain and it is common to need to stay at home for 1-2 weeks. The incubation period, ie time from infection to onset, is about 1-4 days. As long as you have a fever, you are usually considered contagious.

In the elderly, pregnant women and people with chronic diseases, the flu can develop into a serious illness that can even be life-threatening. Elderly and chronically ill people who get the flu become extra susceptible to other infections such as pneumonia, sepsis and meningitis. Therefore, these groups are also offered vaccines against the bacterium pneumococci, the most common bacterium to cause these infections. 

Vaccine against influenza

VaccinDirekt offers the 2020/2021 flu vaccine season, which protects against four different strains of influenza (2 so-called A strains and 2 B strains), which provides broader protection compared with previous years when many received a vaccine that covered three strains. The flu vaccine is given in the upper arm muscle.

In young children, the vaccine is given in the thigh muscle. It takes 2-3 weeks after vaccination until you have protection against disease. The protection lasts for 6-12 months, shorter time in the elderly and people with lowered immune systems. Vaccinating you reduces the risk of severe flu and complications as well as sequelae by about 50 percent. VaccinDirekt’s Influence Campaign 2020/2021.


Read more about flu in our articles

Influenza in pregnant women

Flu symptoms

Influenza in children