What you need to know about the flu shot

Flu season comes around every year. And each year, the flu vaccine is one of the best tools we have to lower the risk of flu and its potentially serious complications. The Centers for Disease Control and Prevention (CDC) recommends a yearly flu vaccine for everyone ages 6 months and older, with rare exceptions.

While the flu shot can’t guarantee you won’t get sick, it can help lower your risk of flu and make serious illness less likely.

Key takeaways: 

• The CDC recommends an annual flu vaccine for everyone 6 months and older, with rare exceptions

• Flu vaccines cannot cause the flu—they use inactivated viruses, a single viral protein or weakened viruses

• Protection takes about two weeks to fully develop after vaccination

• Getting vaccinated in early fall is ideal, but it’s still worthwhile later in the season

• Most people with egg allergies can safely receive any flu vaccine

• Mild, short-lived side effects (soreness, low-grade fever, muscle aches) are common and not a sign of illness

Why get the flu vaccine?

The flu vaccine lowers your risk of flu and reduces the chances of severe illness if you do get sick. The flu can be more than a few days of fever, chills and body aches. It can lead to serious complications, especially for young children, older adults, pregnant people, and people with certain chronic health conditions. According to the CDC, flu has resulted in between 9.4 million and 51 million illnesses, 120,000 and 710,000 hospitalizations, and 6,300 and 52,000 deaths annually in the U.S. since 2010.

Getting a flu vaccine each year helps your body prepare for the flu viruses expected to circulate during the season and can reduce the risk of severe illness if you do get sick.

How does the flu vaccine work?

The flu vaccine teaches your immune system to recognize flu viruses and build antibodies that can help protect you if you’re exposed later. It takes about two weeks for this protection to develop.

When should you get the flu vaccine? 

Early fall is generally best, though vaccination is worthwhile any time the flu is circulating. Ideally, you’d get vaccinated before flu activity begins to increase in your community. For many people, that means getting vaccinated in early fall. Even if you miss the early fall window, it can still be worthwhile to get vaccinated later in the season.

Some people may need different timing. For example, children ages 6 months through 8 years who need two doses should get the first dose as soon as the vaccine is available. People who are pregnant, adults ages 65 and older, and people with certain health conditions may have specific recommendations about when to get vaccinated or which vaccine to receive.

Can the flu vaccine give you the flu?

No. Flu vaccines cannot cause the flu. Flu shots are made with either inactivated viruses or a single flu-virus protein, and the nasal spray vaccine uses weakened viruses that are designed not to cause flu illness.

Some people have mild side effects after vaccination. These can include soreness where the shot was given, headache, low-grade fever or muscle aches. These side effects are usually mild and short-lived.

Who should not get a flu vaccine?

There are a few situations in which a specific flu vaccine may not be recommended because of a person’s age, health condition or history of severe allergic reaction.

Examples may include people who have had a severe allergic reaction to a flu vaccine or to a vaccine ingredient. The nasal spray flu vaccine is also not recommended for some groups, including pregnant people and people with certain health conditions.  

If you are unsure which flu vaccine is right for you, your care team or pharmacist can help you choose an option based on your age, health history and allergies.

I have an egg allergy. Do I need to avoid the flu vaccine?

No, not in most cases. Most people with an egg allergy can receive any flu vaccine, including both egg-based and non-egg-based flu options.