Influenza (the flu) is caused by a virus which exists all over the world. There are three types of influenza virus which can infect humans, type A, B, and C. Influenza type A causes the largest epidemics, while infection with type C usually only causes symptoms similar to the common cold. Furthermore, there are special types of influenza virus affecting specific animals, e.g. avian flu. These are only rarely contagious to humans. The influenza virus has a high capacity to change characteristics (mutate). The infection is air-borne and circulates every winter in Sweden. It usually reaches peak intensity around January and February.


Most cases of influenza cause fever (usually 39-40 degrees centigrade), a runny nose, cough, headache, and muscle aches. It is common to need to stay home for 1-2 weeks. The incubation time (i.e. time from infection until development of symptoms) is approx. 1-4 days. Normally you are contagious while you have a fever.

In the elderly, pregnant women, and people with chronic conditions, influenza can develop into a serious disease which can potentially be life-threatening. Furthermore, influenza infection predisposes you to other infections such as pneumonia, septicemia, and meningitis. For this reason, these groups are offered both vaccination against influenza and pneumococcus (the most common cause of pneumonia).

Vaccine against influenza

At VaccinDirekt we offer a quadrivalent (four strains, two A-strains and two B-strains) influenza vaccine for the season 2018/2019. The vaccination is given in the shoulder muscle except for children under two who receive it in the thigh. The vaccine takes about 2-3 weeks until full protection, which lasts 6-12 months. By getting vaccinated the risk of serious influenza and complications is reduced by approx. 50 %.

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