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Influenza (Flu)

It is important to receive an annual flu vaccine to protect yourself and the other people in your community from contracting the flu and prevent the spread of this potentially dangerous disease.

What is seasonal influenza (flu)?

Seasonal influenza, commonly called "the flu" is caused by influenza viruses, which infect the respiratory tract (i.e., the nose, throat, lungs). Unlike many other viral respiratory infections, such as the common cold, the flu can cause severe illness and life-threatening complications in many people.

In the United States, each year on average 3% to 11% of the population gets the flu. Flu seasons are unpredictable and can be severe. The CDC estimates that flu has resulted in 9 million – 41 million illnesses, 140,000 – 710,000 hospitalizations and 12,000 – 52,000 deaths annually between 2010 and 2020.

Flu vaccines protect against the influenza viruses that research indicates will be most common during the upcoming season. Everyone 6 months and older should get vaccinated against the flu every year. Get vaccinated soon after vaccine becomes available in your community, if possible by October. Immunity sets in about two weeks after vaccination.

(May 3, 2022) CDC: Influenza (Flu), Disease Burden of Flu, Retrieved from
(May 3, 2022) CDC: Influenza (Flu), Frequently Asked Questions about Estimated Flu Burden, Retrieved from

What are symptoms of the flu?

Fever, chills, fatigue, body aches, sore throat, and headache are common symptoms of flu. Not everyone with flu will have a fever. The flu can cause mild to severe illness, and at times can lead to death. The flu is different from a cold. The flu usually comes on suddenly.

For information about flu symptoms, see CDC Flu Symptoms & Complications.

When is the flu season in the United States?

In the United States, flu season occurs in the fall and winter. The peak of flu season has occurred anywhere from late November through March. The overall health impact (e.g., infections, hospitalizations, and deaths) of a flu season varies from year to year. CDC monitors circulating flu viruses and their related disease activity and provides influenza reports (called "FluView") each week from October through May. See Weekly U.S. Influenza Summary Update. Flu surveillance in the U.S. continues through the summer months with condensed reports available.

Do I really need a flu vaccine every year?

Yes. CDC recommends a yearly flu vaccine for just about everyone 6 months and older, even when the viruses the vaccine protects against have not changed from the previous season. The reason for this is that a person's immune protection from vaccination declines over time, so an annual vaccination is needed to get the "optimal" or best protection against the flu.

(April 8, 2024) CDC: Influenza (Flu), Seasonal Influenza Q&A Retrieved from