Every fall, my physician insists on the importance of my receiving the flu vaccine. I am not convinced that this is necessary. Is this vaccine really effective? Isn’t it dangerous to be vaccinated year after year? How do you explain the flu-like side effects that some people experience?
Before answering this question, I would like to provide a few details about the flu. The “real” flu is caused by influenza viruses. There are only a few dozen of these viruses, but they cause respiratory infections that are usually more serious than a simple cold, which is caused by other, far more numerous respiratory viruses. While the flu is accompanied by high fever, headache, and muscular pain in addition to respiratory symptoms (sore throat, nasal congestion, cough), colds consist of respiratory symptoms without the other symptoms, except perhaps a slight fever. Viral respiratory infections may be complicated by bacterial infections (earache, sinusitis, bronchitis, pneumonia). These complications are more frequent and serious with the flu than with a cold, and are more prevalent in older people and in those with chronic diseases, such as cystic fibrosis. This is why it is important for these two groups of people to receive protection.
Fortunately, the influenza (flu) vaccine has been around for many years now. However, it offers no protection against the numerous cold viruses. The vaccine is 80% effective in young adults; however, it must be administered annually because it does not provide long-term protection and is directed against a different selection of viruses every year.
In addition to causing slight sensitivity at the site of the injection, the vaccine may sometimes cause light flu symptoms: low-grade fever with muscular pain, with or without minor respiratory symptoms. These side effects usually last 24 to 48 hours at the most. They are caused by the mobilization of the immune system (white blood cells and antibodies), which is responding to the vaccine.