Influenza is an upper respiratory infection known as the flu. It is caused by a strain of the influenza virus. There are many types of these viruses but the two that most often infect humans include:
Each year the flu spreads around the world. It spreads most often from person to person. Someone who is infected releases the virus through droplets in sneezes or coughs. Others inhale these droplets, then become sick. The virus can also land on a surface. Someone can become infected if they touch the surface then touch their mouth or nose. For most, the flu will cause fever, aches, fatigue, coughing, stuffiness, and sore throat. Some people have a higher risk of a severe infection. It may lead to hospital care. Risk factors for severe complications include:
There are different types of flu vaccine. There are 3 types of flu shots available:
Vaccines lets the body prepare for the flu virus. Within a few days of the vaccine, the body makes tools to help find and fight any flu virus that enters the body. A doctor will help to find which shots will be best for each person. Age and overall health will play a role in the decision. The shots need to be given each year. The strains included in the vaccine will change from year to year. The strains are based on which viruses are likely to spread during that flu season. You may still get the flu if you get a flu strain that was not included in the vaccine. However, you may have a less severe infection. If you have symptoms, tell your doctor.
The Centers for Disease Control and Prevention (CDC) recommend that anyone aged 6 months and older should get a flu shot. It should be done every year.
It takes about 2 weeks for the vaccine to have full effect. The best time to get a flu shot is as soon as the shot is available. This will protect you before the flu comes to your community.
The flu shot is safe for almost all people. There is a small risk of serious problems such as severe allergic reaction.
Minor side effects associated with the flu shot include:
Minor side effects associated with the nasal spray vaccine include:
There is a higher risk of problems from the flu shot in people with one or more of the following:
The following people should not get the nasal spray:
Habits that may decrease your exposure to the flu virus include:
To reduce spread of flu to others, cover your nose and mouth when you cough or sneeze. Use your elbow or a tissue as cover.
If an outbreak has started in your community, get a flu shot if you have not had one. The more people who have had flu shots the safer the community will be. Viruses will have a harder time passing from person to person if most have had the flu shot. Follow other precautions like washing your hands even if you have had the flu shot.
WHERE CAN I GET MORE INFORMATION?
Centers for Disease Control and Prevention
Public Health Agency of Canada
US Food & Drug Administration
Key factors about influenza vaccine. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/flu/prevent/keyfacts.htm#match. Updated September 16, 2018. Accessed May 10, 2019.
Influenza in adults. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T435301/Influenza-in-adults . Updated April 18, 2019. Accessed May 10, 2019.
Influenza in children. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T435305/Influenza-in-children . Updated October 29, 2018. Accessed May 10, 2019.
Seasonal influenza vaccines in adults. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T258149/Seasonal-influenza-vaccines-in-adults . Updated September 13, 2018. Accessed May 10, 2019.
Seasonal influenza vaccines in children. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T268332/Seasonal-influenza-vaccines-in-children . Updated September 26, 2018. Accessed May 10, 2019.
Seasonal influenza vaccines in the elderly. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T912559/Seasonal-influenza-vaccines-in-the-elderly . Updated November 28, 2018. Accessed May 10, 2019.
Last reviewed September 2018 by
EBSCO Medical Review Board
Marcie L. Sidman, MD
Last Updated: 5/10/2019