Should you get a flu shot if you already had the flu?

The first step in preventing the flu, the Centers for Disease Control and Prevention (CDC) says, is getting a flu shot every year. Seems simple, right? But what if you already had the flu this season — does the advice stand?

It does. That is because the flu shot has been proven to reduce flu illness, serious flu complications, and hospitalization or death due to the flu. Vaccination, even after having flu-related illness, is recommended for everyone age 6 months and older with rare exception.

Why should I get a flu shot every year?

According to the CDC, the protection the annual vaccine provides declines over time. Additionally, the viruses that cause flu-related illness change constantly.

Therefore, each year in February, the Food and Drug Administration (FDA) reviews all the information on flu activity — where cases of flu are occurring; which viruses are circulating; and how flu is affecting illness, hospitalizations and deaths — around the world and determines which strains are most likely to cause flu in the upcoming season. The vaccines are then updated to protect against those specific viruses.

“There are many strains of influenza,” says Dr. Stacey Coleman, a Sharp Rees-Stealy Medical Group family medicine doctor. “The FDA does their best educated guessing to put together a vaccine that will cover the most common strains of flu, but there are always others.”

Getting the annual flu shot after having flu-like illness is also vital because:

• You may have gotten sick from a strain that is not covered by the vaccine.

• Your illness could be caused by one of the four strains covered, leaving you unprotected against the other three strains if you are not vaccinated.

• You may have had symptoms — such as fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills or fatigue — that led you to believe you had the flu. But without a laboratory-confirmed test to prove a diagnosis, those symptoms might have been from a different respiratory illness.

What’s more, while both flu illness and vaccination provide immunity, receiving the vaccine to further lower risk of infection is especially important for people at risk of severe illness. “The potential for disease can be dramatic for those at risk,” Dr. Coleman says.

Complications of flu can include:

• Bacterial pneumonia

• Ear infections

• Sinus infections

• Worsening of chronic medical conditions, such as congestive heart failure, asthma or diabetes

Other ways to prevent the flu

Along with getting your annual flu shot, Dr. Coleman recommends taking the following preventive actions to protect yourself and others:

• Avoid people who are sick.

• Stay home if you are sick.

• Cover your coughs and sneezes.

• Regularly wash your hands with soap and water or use a hand sanitizer with at least 60% alcohol.

• Avoid touching your eyes, nose and mouth.

• Clean and disinfect regularly touched surfaces.

• Stay home for at least 24 hours after your fever is gone (without the use of fever-reducing medication).

Dr. Coleman also recommends waiting at least two weeks after a flu diagnosis before receiving your annual flu shot. And wait until symptoms of other illnesses resolve before getting vaccinated. You can receive both your flu shot and COVID-19 vaccine or booster at the same time, but experts suggest receiving them in different arms.

Learn how to get a flu vaccine, view frequently asked questions about the flu and more.