When Is Flu Season?

Although flu season is usually thought of as occurring in the winter, the severity and timing vary from year to year. To best protect yourself regardless of the specific timeframe, the Centers for Disease Control and Prevention (CDC) recommends getting vaccinated by the end of October.

In general in the United States, flu season can start anytime in late fall, peak in mid-to-late winter (between December and February), and continue through early spring. On average, flu season lasts about 13 weeks. It will usually end by April, but in some years it can linger into May.

It is a good idea to get a flu shot before the start of flu season so that you don't get sick with the flu, but even a late flu shot provides protection, especially when flu season lingers into April or May.

The strain of influenza that circulates can change from year to year, and the vaccine is adjusted in an attempt to predict which will predominate. Here is a look at the flu over the last 10 years:

• Peak: Mid-February
• Most common strain: Influenza A—both H3N2 and H1N1

• Peak: January and February
• Most common strain: Influenza A (H3N2)

• Peak: Mid-March
• Most common strain: Influenza A (H3N2)

• Peak: Mid-March
• Most common strain: 2009 H1N1 Influenza A

• Peak: Late December
• Most common strain: Influenza A (H3N2)

• Peak: Late December
• Most common strain: 2009 H1N1 Influenza A

• Peak: Late December
• Most common strain: Influenza A (H3N2)

• Peak: Mid-March
• Most common strain: Influenza A (H3N2)

• Peak: Early February
• Most common strain: Influenza A (H3N2)

The CDC recommends that everyone over the age of 6 months get the yearly flu vaccine and that you get it as soon as it becomes available, by the end of October, if possible. It takes about two weeks after vaccination for your body to produce the antibodies that will protect you from the flu. But if you missed the earlier vaccination time, it is still valuable to get the vaccine even in January or later.