Seasonal influenza



Influenza, more commonly known as ‘the flu’, is a highly contagious disease which can cause mild to severe illness and even death, particularly for those in the high-risk groups (the very young, the older population, those with an underlying health condition, those who are pregnant, overweight or who have a weakened immune system). Symptoms usually last between 3 and 7 days, although in some instances these can persist for several weeks. Recovering from flu generally takes one or two weeks, and sometimes more.

The virus spreads through water droplets, especially when an infected person coughs or sneezes, or via contaminated hands and surfaces.

Hygiene measures such as washing of hands, coughing into your elbow, and keeping your distance, are good habits to keep up, as they are effective in helping to reduce our chances of contracting and/or spreading the flu virus. However, the vaccine remains the best way to protect yourself and others against flu, to prevent the spread of the disease and to reduce its severity.


It is important to get a flu shot every year to keep up with the circulating variants of the influenza virus and thus avoid being bed-ridden or developing complications. 

The infirmary will vaccinate any person working on the CERN site (MPE, MPA, temporary workers and contractors) provided the person brings their own vaccine and that the relevant medical questionnaire at the infirmary confirms there are no contraindications to vaccination. Note that both conditions have to be met for the vaccination to be administered. A medical prescription will be given to the patient after the vaccination to allow the reimbursement of the vaccine by the person’s health insurance provider.

Vaccination in France | Ameli (available in French only)
Vaccination in Switzerland | OFSP

Contraindications for the flu vaccine

Under certain conditions, precautions must be taken when administering the vaccine.

People with a fever should only get their vaccine after all symptoms have disappeared, as their immune response could be diminished.

Vaccination is not recommended for people suffering from allergies to the vaccine’s components or egg protein. Flu vaccination is recommended for pregnant women, whatever the stage of pregnancy.

Possible side effects from vaccination

There is a much higher risk of complications due to catching the flu virus itself than any undesirable effects linked to the vaccination.

Among possible side effects, the most frequent (for 10 to 40% of vaccinated persons) are a redness or slight pain at the site of injection. Other symptoms such as fever, muscular pain or slight nausea can also be observed for 5 to 10% of vaccinated persons. These are minor reactions and will disappear after a few days.

General information about influenza

General information on Influenza | WHO
General information on Influenza in Switzerland | OFSP (available in French only)