What is the flu vaccine?

The flu vaccine is the most effective weapon of prevention against influenza season, pathology of the respiratory tract due to so-called influenza viruses. Influenza is a serious disease that can lead to hospitalization and sometimes even death. A flu vaccine is given with a needle, usually in the arm. It causes antibodies to develop in the body about two weeks after vaccination. These antibodies provide protection against infection with the viruses that are in the vaccine. The flu vaccine is the best way to reduce the chances of getting seasonal flu and spreading it to other individuals. The more individuals get vaccinated against the flu, the less the flu can spread through that area.



What is the flu vaccine composed of?

In Italy, the flu vaccine is said to be trivalent because it contains three types of virus: two influenza type A viruses (H1N1 and H3N2) and an influenza type B virus. In addition, flu vaccines made to protect against 4 different flu viruses are called quadrivalent vaccines. A quadrivalent vaccine contains two type A viruses (H1N1 and H3N2) and two influenza type B viruses.


The virus contained in the vaccine is selected on the basis of viruses isolated during the previous season. Thus, the efficiency of the vaccine depends on the correspondence between the viruses that it contains and those circulating currently, which can also be different.The flu vaccine is administered intramuscularly in the arm in children from 9 years of age and in the anterolateral thigh region in younger children.



When is it recommended to receive the flu vaccine?

In Italy, it is possible to receive the flu vaccine in autumn, as the vaccination campaign typically takes part in mid-October and ends in late December. This period has been established as the best time for receiving flu vaccines, taking into account the climatic conditions and the occurrence of the Italian influenza epidemics.


Any individual can receive a flu vaccination, as no contraindications are established. There are, however, some individuals who are at higher risk. Here are a few examples:

  • Women who are pregnant (at their second or third trimester of pregnancy at the start of the epidemic season)
  • Certain workers such as police and firefighters
  • Certain workers who are in contact with animals (potential source of infection)
  • Individuals over the ages of 65
  • Children (over 6 months) and adults (up to ages 65), suffering from diseases that can expose them to major complications of influenza (such as chronic respiratory diseases, cardiovascular diseases, metabolic diseases and tumors) 



What are the side effects of the flu vaccine?

The flu vaccine is very safe. Following administration, only a slight pain may be felt at the injection site. Mild symptoms that may occur include the following:

  • Redness at the injection site
  • Soreness at the injection site
  • Swelling
  • Fever
  • Headache
  • Muscle aches
  • Pain in the muscle joint


Like all vaccines, there is the possibility of serious problems occurring, such as thrombocytopenia, neuralgia, paresthesias, neurological disorders and severe allergic reactions. Although rare, there appears to be a correlation between the flu vaccine and the onset of the listed disorders.