Editorial note: Content for the Q&A is from the Centers for Disease Control and Prevention (CDC). Find all of CDC’s information about the flu. 

Chills. Body aches. Fatigue. These are just a few of the symptoms people often experience when they get influenza, or more commonly called flu. Your best defense against it? A yearly flu shot. Since it’s officially flu season, here are some questions — and answers — about flu and the vaccine. You’ll get the basic information you need to keep yourself and your family healthy this season.

What is influenza (also called flu)?

The flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. It can cause mild to severe illness and at times can lead to death. The best way to prevent the flu is by getting a flu vaccine each year.

How does it spread?

Most experts believe that flu viruses spread mainly by tiny droplets made when people with flu cough, sneeze, or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or possibly their eyes.

How can you prevent the flu?

The first and most important step in preventing flu is to get a flu vaccination each year. The CDC also recommends everyday preventive actions (like staying away from people who are sick, covering coughs and sneezes, and frequent handwashing) to help slow the spread of germs that cause respiratory (nose, throat, and lungs) illnesses, like flu.

What is the flu shot?

The flu shot is a vaccine given with a needle, usually in the arm. The seasonal flu shot protects against the three or four influenza viruses that research indicates will be most common during the upcoming season.

Who should get vaccinated?

Everyone 6 months and older should get a flu vaccine every season. Vaccination to prevent influenza is particularly important for people who are at high risk of serious complications from influenza.

People at high risk for developing flu-related complications include children under 5, but especially children under 2; adults 65 and older; pregnant women or women who have recently given birth; residents living in nursing homes or other facilities; American Indians and Alaskan Natives; and people living with health conditions, such as asthma, lung disease, and heart disease. However, there are some people who should not get the vaccine or should talk to their doctor first.

Can a flu shot give you the flu?

No, a flu shot cannot cause flu illness. Flu vaccines given with a needle are currently made in two ways: the vaccine is made either with a) flu vaccine viruses that have been ‘inactivated’ and are therefore not infectious, or b) with no flu vaccine viruses at all (which is the case for recombinant influenza vaccine).

What are the most common side effects?

The most common side effects from the influenza shot are soreness, redness, tenderness, or swelling where the shot was given. Low-grade fever, headache, and muscle aches also may occur.

What about serious reactions to flu vaccine?

Serious allergic reactions to flu vaccines are very rare. If they do occur, it is usually within a few minutes to a few hours after the vaccination. While these reactions can be life-threatening, effective treatments are available.

Is it better to get the flu than the flu vaccine?

No. Flu can be a serious disease, particularly among young children, older adults, and people with certain chronic health conditions, such as asthma, heart disease, and diabetes. Any flu infection can carry a risk of serious complications, hospitalization, or death, even among otherwise healthy children and adults. Therefore, getting vaccinated is a safer choice than risking illness.

Why do I need a flu vaccine every year?

A flu vaccine is needed every season for two reasons. First, the body’s immune response from vaccination declines over time, so an annual vaccine is needed for optimal protection. Second, because flu viruses are constantly changing, the formulation of the flu vaccine is reviewed each year and sometimes updated to keep up with changing flu viruses. For the best protection, everyone 6 months and older should get vaccinated annually.

Does flu vaccine work right away?

No. It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection. That’s why it’s better to get vaccinated early in the fall, before the flu season really gets under way.

Where can I get a flu vaccine?

Flu vaccines are offered in many locations, including doctor’s offices and clinics. Even if you don’t have a regular doctor or nurse, you can often get a flu vaccine somewhere else, like a health department, pharmacy, urgent care clinic, school, college health center, or workplace. The Vaccine Locator is a useful tool for finding a place to get vaccinated in your area.