A doctor speaks with a patient in an exam room.

Common questions about the flu shot answered, thanks to the Centers for Disease Control and Prevention (CDC).

Do flu shots work?

Getting a flu shot during flu season can reduce the risk of getting sick with the flu by approximately 50–60%, according to recent studies by the CDC.1

When should I get a flu shot?

Flu season may begin as early as September. The CDC recommends getting a flu shot every year by the end of October, but you can get vaccinated through January, or even later. It takes about 2 weeks for the flu shot to help protect you against viruses, so getting it in the fall is recommended.2

Should I get vaccinated?

The CDC recommends everyone 6 months of age and older receive an annual flu shot, with some rare exceptions for age, health history and allergies.

There are other options for those with allergies or health risks—talk to your doctor about which flu vaccination is right for you.

Flu vaccines: should I get a flu vaccine?

What are the different flu vaccines?

There are different types of flu vaccines, so make sure to ask your doctor which flu vaccine is right for you, especially if you have allergies, are more likely to get the flu, or are pregnant.

What if I got the flu shot last year?

Each year the flu shot is different and helps protect us from several different viruses that are expected to be most common that season. The viruses this year may be different from the previous year, so it’s important to get a new flu shot every year.

What if the flu shot doesn’t work?

Sometimes different types of a flu virus start spreading and you may get a different strain of the flu that wasn’t contained in your flu shot. If you think you may be sick with the flu, call your doctor as soon as possible.

Are there side effects of the flu shot?

Side effects are possible with any medicine or vaccine. Potential side effects are typically mild, but serious reactions, such as fainting, are possible.

Mild side effects include soreness, redness or swelling where the shot was given, fever, aches, or other minor symptoms. If these minor side effects occur, it is typically soon after the shot is administered and symptoms may last for up to 2 days.

Can the flu shot give me the flu?

No, the flu shot does not cause the flu. However, if you are exposed to the flu before receiving the shot or before the shot becomes fully effective, you may get the flu.

What if I already have the flu?

Visit your doctor or an urgent care clinic right away. Your healthcare provider may be able to provide an anti-viral drug to help relieve your symptoms.

Caring for yourself and loved ones during the flu season

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  1. “Vaccine Effectiveness - How Well Does the Flu Vaccine Work?” Centers for Disease Control and Prevention, last accessed January 15, 2021, https://www.cdc.gov/flu/vaccines-work/vaccineeffect.htm, opens new window.
  2. “Key Facts About Seasonal Flu Vaccine,” Centers for Disease Control and Prevention, last accessed January 15, 2021, https://www.cdc.gov/flu/prevent/keyfacts.htm, opens new window.