The flu, short for influenza, is a respiratory disease caused by the influenza virus. Some common symptoms are fever, cough, sore throat, runny nose, muscle aches and fatigue. The flu season usually runs from October through May.

The seasonal flu shot is a vaccine taken to protect against the flu every year. According to the Centers for Disease Control and Prevention (CDC), flu shots are recommended for all Americans over the age of 6. As the strains of the virus keep changing, a new vaccine is made every year based on predictions about how the strains will evolve.

The 2016 to 2017 season

According to the CDC, a projected number of 157 million to 168 million doses of injectable flu vaccine will be available for the 2016-2017 season.

The shots are made using egg-based technology — with small amounts of egg protein — and in the past, the CDC had recommended that those suffering from egg allergies should be monitored for 30 minutes after receiving a flu shot. This recommendation does not stand any longer.

The CDC has also said that the flu nasal spray is not recommended for anyone this season, as new data showed that the nasal spray was not very effective between 2013 and 2016.

When should you get a flu shot?

Health officials recommend that people get their flu shot in early fall — by the end of October, as the exact duration of the season is not predictable. Each season’s shot expires in June every year. After taking the shot, a person takes almost two weeks to build up immunity against the flu.

Who should not get a flu vaccine?

Children under 6 months cannot get a flu shot, in addition to those who have previously had a severe allergic reaction to a flu vaccine. Even people suffering from high fever are recommended to wait until the fever subsides to take the shot.

Studies show flu vaccines are safe for women in any stage of pregnancy, according to the CDC. Also, vaccination during pregnancy helps to protect the child against flu while they cannot be administered the vaccine.

What are the side effects?

There are mild side effects of the flu shot — soreness, redness or swelling at the injection site, low-grade fever and aches. More serious side effects like allergic reactions are rare.

The side effects last a short time compared to the actual flu, the CDC said.

Can the flu shot give you the flu?

There exists a myth that you can get the flu from the flu vaccine. However, the viruses in the flu shot are either inactivated and thus, noninfectious, or do not contain flu vaccine viruses at all, so people cannot get the flu from a flu vaccine. As it takes almost two weeks to build up immunity after the vaccine, some people may catch the flu during this time period, if exposed to the virus.