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Frequently asked questions

A. There are some similarities and big differences. Like the common cold, the flu virus infects the respiratory system. Some symptoms may seem similar, too, but the flu is different from a cold. It can cause mild to severe illness and may even lead to death.1,2 For some people who already have certain health conditions, getting the flu can lead to dangerous complications like pneumonia, heart attacks, and strokes.2,3
A. No. The viruses circulating in the environment may change from year to year, so even if you got the flu or a flu shot last year, you could still be vulnerable to new flu viruses this year.4 In addition, the length of time the immunity lasts is limited, and how long your individual immunity lasts also can be affected by your age and the condition of your health. If you’re aged 65 years or older, your immunity may decline even more quickly. This means that you might still be vulnerable to the same flu virus and its complications a year after being infected or having a flu shot.4
A. Flu season in the United States occurs in the fall and winter, and sometimes early spring since it can last into May.1 An annual flu shot early in the season is still your best defense against getting the flu.1
A. Vaccines are not 100% effective, and sometimes the influenza virus in one year’s flu shot does not match the virus that appeared during that flu season.1 The World Health Organization, in collaboration with the CDC’s Influenza Division, makes recommendations to the FDA about which viruses the flu shot should contain each year.5 Because the flu is unpredictable,2 even the most carefully predicted viruses may not match the viruses that arise in a given flu season.1 Still, your best protection is getting a flu shot, especially if you are aged 65 years or older.6
A. Just because you’ve been lucky in the past, doesn’t mean you will be in the future. Studies have shown that as we grow older, our immune systems do, too. Your immune system may start to weaken, which reduces your resistance to the flu.7 If you also have a condition such as diabetes, heart disease, or chronic lung disease, the flu can make these conditions worse.8,9 The CDC recommends that the best way to prevent the flu is to get a flu shot every year as soon as they are available, usually in October.6
A. In addition to getting a flu shot, you can take preventive measures such as washing your hands frequently to reduce the spread of germs and staying away from others who may be sick. If you become sick with the flu, stay home to keep from infecting others.6


Here are other good sources of information about the flu: