Influenza (flu) is a contagious disease. It is caused by the influenza virus, which can be spread by coughing, sneezing, or nasal secretions. Other illnesses can have the same symptoms and are often mistaken for influenza. But only an illness caused by the influenza virus is really influenza.
Anyone can get influenza, but rates of infection are highest among children. For most people, it lasts only a few days. It can cause: fever, sore throat, chills, fatigue, cough, headache, and muscle aches.
Some people get much sicker. Influenza can lead to pneumonia and can be dangerous for people with heart or breathing conditions. It can cause high fever, diarrhea and seizures in children. On average, 226,000 people are hospitalized every year because of influenza and 36,000 die - mostly elderly.
Influenza vaccine can prevent influenza.
There are two types of influenza vaccine:
- Live, attenuated influenza vaccine (LAIV) contains live but attenuated (weakened) influenza virus. It is sprayed into the nostrils.
- Inactivated influenza vaccine, sometimes called the ''flu shot,'' is given by injection. This vaccine is described in a separate monograph.
Influenza viruses are always changing. Because of this, influenza vaccines are updated every year, and an annual vaccination is recommended.
Each year scientists try to match the viruses in the vaccine to those most likely to cause flu that year. When there is a close match the vaccine protects most people from serious influenza-related illness. But even when the there is not a close match, the vaccine provides some protection. Influenza vaccine will not prevent “influenza-like” illnesses caused by other viruses.
It takes about 2 weeks for protection to develop after the vaccination. Protection lasts up to a year.
LAIV does not contain thimerosal or other preservatives.
LAIV is approved for people from 2 through 49 years of age, who are not pregnant and do not have certain health conditions. Influenza vaccination is recommended for people who can spread influenza to others at high risk, such as:
- Household contacts and out-of-home caregivers of children up to 5 years of age, and people 50 and older.
- Physicians and nurses, and family members or any one else in close contact with people at risk of serious influenza.
Health care providers may also recommend a yearly influenza vaccination for:
- People who provide essential community services.
- People living in dormitories, correctional facilities, or under other crowded conditions, to prevent outbreaks.
Influenza vaccine is also recommended for anyone who wants to reduce the likelihood of becoming ill with influenza or spreading influenza to others.
LAIV is not licensed for everyone. The following people should get the inactivated vaccine (flu shot) instead:
- Adults 50 years of age and older or children between 6 months and 2 years of age. (Children younger than 6 months should not get either influenza vaccine.)
- Children younger than 5 with asthma or one or more episodes of wheezing within the past year.
- People who have long-term health problems with heart disease; kidney or livier disease; lung disease; metabolic disease, such as diabetes; asthma; anemia, and other blood disorders.
- Anyone with certain muscle or nerve disorders (such as seizure disorders or cerebral palsy) that can lead to breathing or swallowing problems.
- Anyone with a weakened immune system.
- Children or adolescents on long-term aspirin treatment.
- Pregnant women.
Tell your doctor if you ever had Guillain-Barré syndrome (a severe paralytic illness also called GBS). You may be able to get the vaccine, but your doctor should help you make the decision.
The flu shot is preferred for people (including healthcare workers, and family members) in close contact with anyone who has a severely weakened immune system (requiring care in a protected environment, such as a bone marrow transplant unit). People in close contact with those whose immune systems are less severely weakened (including those with HIV) may get LAIV. Anyone with a nasal condition serious enough to make breathing difficult, such as a very stuffy nose, should get the flu shot instead.
Some people should talk with a doctor before getting either influenza vaccine:
- Anyone who has ever had a serious allergic reaction to eggs or another vaccine component, or to a previous dose of influenza vaccine. LAIV also contains MSG, arginine, gentamicin, and gelatin.
- People who are moderately or severely ill should usually wait until they recover before getting flu vaccine. If you are ill, talk to your doctor or nurse about whether to reschedule the vaccination. People with a mild illness can usually get the vaccine.
Plan to get influenza vaccine in October or November if you can. But getting it in December, or even later, will still be beneficial in most years. You can get the vaccine as soon as it is available, and for as long as illness is occurring in your community. Influenza illness can occur any time from November through May, but it most often peaks in January or February.
Most people need one dose of influenza vaccine each year. Children younger than 9 years of age getting influenza vaccine for the first time, or who got influenza vaccine for the first time last season but got only one dose, should get two doses, at least 4 weeks apart, to be protected.
LAIV may be given at the same time as other vaccines.
A vaccine, like any medicine, could possibly cause serious problems, such as severe allergic reactions. The risk of a vaccine causing serious harm, or death, is extremely small. Live influenza vaccine viruses rarely spread from person to person. Even if they do, they are not likely to cause illness. LAIV is made from weakened virus and does not cause influenza. The vaccine can cause mild symptoms in people who get it (see below).
Mild Problems (In children and adolescents 2-17 years of age):
- runny nose, nasal congestion or cough
- headache and muscle aches
- fever
- wheezing
- abdominal pain or occasional vomiting or diarrhea
Mild Problems (In adults 18-49 years of age):
- runny nose or nasal congestion
- cough, chills, tiredness/weakness
- sore throat
- headache
These symptoms did not last long and went away on their own. Although they can occur after vaccination, they may not have been caused by the vaccine.
Severe Problems:
- Life-threatening allergic reactions from vaccines are very rare. If they do occur, it is usually within a few minutes to a few hours after the vaccination.
- If rare reactions occur with any product, they may not be identified until thousands, or millions, of people have used it. Millions of doses of LAIV have been distributed since it was licensed, and no serious problems have been identified. Like all vaccines, LAIV will continue to be monitored for unusual or severe problems.
What should I look for?
- Any unusual condition, such as a high fever or behavior changes. Signs of a serious allergic reaction can include difficulty breathing, hoarseness or wheezing, hives, paleness, weakness, a fast heart beat or dizziness.
What should I do?
- Call a doctor, or get the person to a doctor right away.
- Tell your doctor what happened, the date and time it happened, and when the vaccination was given.
- Ask your healthcare provider to report the reaction by filing a Vaccine Adverse Event Reporting System (VAERS) form. Or you can file this report through the VAERS website at http://www.vaers.hhs.gov, or by calling 1-800-822-7967. VAERS does not provide medical advice.
A federal program exists to help pay for the care of anyone who has a serious reaction to a vaccine.
For more information about the National Vaccine Injury Compensation Program, call 1-800-338-2382 or visit their website at http://www.hrsa.gov/vaccinecompensation.
- Ask your immunization provider. They can give you the vaccine package insert or suggest other sources of information.
- Call your local or state health department.
- Contact the Centers for Disease Control and Prevention (CDC): call 1-800-232-4636 (1-800-CDC-INFO) or visit the National Immunization Program's website at http://www.cdc.gov/flu.
Live Attenuated Influenza Vaccine Information Statement. U.S. Department of Health and Human Services/Centers for Disease Control and Prevention National Immunization Program. 7/24/08.
- FluMist®
©2009. All Rights Reserved.
Your use of this information is subject to our User Agreement available at www.ConsumerReportsHealth.org.
