the flu) is an upper respiratory infection. It is caused by a strain of the influenza virus. There are many types of influenza viruses but there are two main kinds that infect humans:
Type AType B
Each year (usually beginning in October), the flu spreads around the world. You can get the flu when you breathe in droplets from someone infected with the virus. It can also be spread by touching a contaminated surface, then putting your hand to your mouth or nose. For most, the flu will cause fever, aches, fatigue, coughing, congestion, loss of appetite, and sore throat. However, some people are more vulnerable to more severe complications which may require hospitalization. Risk factors for severe complications include: Age younger than 5 years old or age 65 years and older
Certain medical conditions, including:
Chronic lung condition, such as
asthma or COPDCardiovascular diseaseKidney or liver diseaseNeurological, blood, or metabolic condition, such as diabetes
Suppressed immune system, such as
those with HIV, cancer, or chronic steroid useCurrent pregnancyLong-term aspirin therapy in people under 19 years oldAmerican Indian and Alaskan Native ancestry
The flu shot is made from an inactivated, killed virus. There are 3 types of flu shots available: Regular flu shot (the most common type)—for people aged 6 months and older, injected into the muscle (usually in the upper arm)High-dose shot (Fluzone High-Dose)—for people aged 65 years and older, injected into the muscleIntradermal shot (Fluzone Intradermal)—for people aged 18-64 years old, injected into the skin with a smaller needle
There is also a nasal spray (FluMist) made from live, weakened flu viruses. The nasal spray is available for healthy people aged 2-49 years who are not pregnant. It is the preferred vaccine for healthy children who are 2-8 years of age.
The flu shots and nasal spray contain several influenza viral strains. The type of strains that the vaccine contains change from year to year. The strains are based on which viruses are likely to circulate during that flu season.
The Centers for Disease Control and Prevention (CDC) recommend that anyone aged 6 months and older should get a flu shot. Children 6 months to 8 years of age will need 2 doses of the vaccine. This will help your child build immunity to the virus.
It takes about 2 weeks for the vaccination to protect you against the flu. Even if you have been vaccinated, you can still get the flu. If you have symptoms, tell your doctor.
You can get the flu anytime during the year. But, flu season typically lasts from October to May. The best time to get vaccinated is as soon as the vaccine is available. This will protect you before the flu comes to your community.
Almost all people who receive the influenza vaccine have no problems. There are certain risks associated with the vaccine. As with any vaccine, there is a small risk of serious problems, including severe allergic reaction.
Side effects associated with the flu shot include: Soreness, redness, and swelling around the injection siteLow-grade feverMuscle aches
Side effects associated with the nasal spray vaccine include: Runny noseHeadacheVomitingMuscle achesFeverSore throatCoughWheezing
Certain people should talk to their doctor before receiving the influenza vaccine. These include people who: Have any severe (life-threatening) allergies to chicken eggsHave had a severe reaction to the flu vaccine in the past
(GBS)Are currently are very sick with a fever
The following people should not get the
Are aged 24 months or youngerHave asthmaAre aged 2-4 years who have had wheezing in the past 12 monthsHave a condition that may increase their risk of flu complications
Are aged 50 years and olderHave a chronic condition, such as heart disease, lung disease, asthma, kidney or liver disease, metabolic disease, blood disordersHave a nerve or muscle disorderHave a weakened immune systemAre in close contact with others who have a weakened immune systemHave a nasal condition which makes it difficult to breathHave gotten any other vaccines in the last 4 weeksHave taken influenza antiviral medication within the previous 48 hoursPregnant womenChildren or teens on long-term aspirin therapy
Good preventive measures include: Avoid close contact with people who have respiratory infections.Wash your hands often for 15-20 seconds with soap and water. This is especially important to do when you come in contact with someone who is sick. Rubbing alcohol-based cleaners on your hands is also useful.Do not share drinks or personal items.Cover your nose and mouth with a tissue when coughing or sneezing.Do not put your hands near your eyes, mouth, or nose.
In the event of an outbreak, the primary focus is to vaccinate as many at risk people as possible, especially those in high priority groups. The use of antiviral medications can reduce the length of the illness when given within two days of onset. Finally, people who are infected should be isolated as much as possible.
WHERE CAN I GET MORE INFORMATION?
Fluzone high-dose seasonal influenza vaccine. Centers for Disease Control and Prevention website. Available at:
http://www.cdc.gov/flu/protect/vaccine/qa_fluzone.htm. Updated September 3, 2015. Accessed August 10, 2015.
Influenza in adults. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed. Updated June 17, 2015. Accessed August 10, 2015.
Influenza in children. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed. Updated July 7, 2015. Accessed August 10, 2015.
Influenza vaccine in adults. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed. Updated August 3, 2015. Accessed August 10, 2015.
Influenza vaccine in children. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed. Updated November 21, 2014. Accessed August 10, 2015.
Key facts about seasonal flu vaccine. Centers for Disease Control and Prevention website. Available at:
http://www.cdc.gov/flu/protect/keyfacts.htm. Updated October 22, 2014. Accessed August 10, 2015.
People at high risk of developing flu-related complications. Centers for Disease Control and Prevention website. Available at:
http://www.cdc.gov/flu/about/disease/high_risk.htm. Updated January 8, 2015. Accessed August 10, 2015.
10/15/2007 DynaMed Systematic Literature Surveillance
http://www.ebscohost.com/dynamed: Nichol KL, Nordin JD, Nelson DB, Mullooly JP, Hak E. Effectiveness of influenza vaccine in the community-dwelling elderly.
N Engl J Med. 2007;357(14):1373-1381.
3/5/2012 DynaMed's Systematic Literature Surveillance
http://www.ebscohost.com/dynamed: FDA approves first quadrivalent vaccine to prevent seasonal influenza. US Food and Drug Administration website. Available at:
http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm294057.htm. Updated March 15, 2012. Accessed August 10, 2015.
8/10/2015 DynaMed's Systematic Literature Surveillance
http://www.ebscohost.com/dynamed: Grohskopf LA, Sokolow LZ, Olsen SJ, et al. Prevention and control of influenza with vaccines: Recommendations of the Advisory Committee on immunization practices, United States, 2015-16 influenza season. MMWR Morb Mortal Wkly Rep. 2015;64(30):818-825.
Last reviewed August 2015 by David Horn, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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