Consumer’s Guide to Flu Vaccines

Everything you need to know about the annual flu shot and how it protects you and those around you from getting sick.

Each fall, medical experts recommend that nearly everyone 6 months and older be vaccinated against the flu — before flu season, which typically starts to ramp up in October, is in full swing.

But even though the flu shot has been around since the 1940s, and has been proven every year since to be the most effective way to prevent infection with the influenza virus, there are lots of misunderstandings and misconceptions about it.

Whether you’re a fan of the flu shot and never miss a season, you’re wary of it, you simply forget about it, or you figure you won’t get sick — and if you do, it won’t be so bad — learning all you can about the vaccine can help you make informed decisions about it going forward.

How Does the Flu Vaccine Work?

Which Flu Strains Does the Vaccine Protect Against?

The flu vaccine is updated every year to match the specific strains of the influenza virus experts predict will be most prominent during flu season. To determine this, the World Health Organization Global Influenza Surveillance Response System, made up of 144 influenza centers in 114 countries, conducts year-round surveillance to determine which flu strains are actively circulating around the globe.

Twice a year, representatives from five of the top participating centers come together to review data and recommend which strains to include in the upcoming flu vaccine.

“These flu experts try to anticipate what the dominant strains are going to be nine months down the road,” explains William Schaffner, MD, professor of infectious disease at Vanderbilt University School of Medicine in Nashville. “They're often on target, but on some occasions, the flu virus that circulates varies from the vaccine. How effective the influenza vaccine is changes from year to year too.”

In other words, flu virus experts have to base their recommendations on a moving target, which means the flu vaccine can’t be perfect. Even so, according to the Centers for Disease Control and Prevention (CDC), the most recent research suggests the flu shot lowers the risk of illness from 40 to 60 percent.

As for the specific influenza strains included in the flu vaccine, for the 2022-2023 season, there are four: two influenza A strains and two influenza B strains. In previous flu seasons, most vaccines protected against only three strains.

5 Essential Facts About the Flu Vaccine

Learning more about the vaccine can help you understand why you should get a flu shot each season and, if you have children, make sure they get vaccinated too.

6 FAQs About the Flu Shot

Who Should and Shouldn’t Get a Flu Shot?

“In regards to influenza, the recommendation could not be simpler: Most healthy people over 6 months old, should be vaccinated,” says Schaffner. This guidance comes with rare exceptions.

Which Vaccination Is Best for Me?


Different vaccines are recommended for different age groups, for pregnant people, or for those who are immunocompromised or have certain health conditions.

For example, according Pekosz, “the flu mist is a good option for children, but isn’t used frequently in other age groups.” Also, this June, the CDC recommended everyone 65 and older get a high-dose or adjuvanted flu vaccine.

Work with your doctor to determine which vaccine is the right match for you, how to access it, and which vaccine to get if the you can’t.

At the end of the day, the goal is to get as many people vaccinated as possible. “We want you to protect yourself, your family, and your community,” says Schaffner. “So please —  get vaccinated.”