Facts About Influenza (Flu) Vaccine
The single best way to protect against the flu is to get vaccinated each fall.
There are two types of vaccines:
- The "flu shot" - an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm. The flu shot is approved for use in people older than 6 months, including healthy people and people with chronic medical conditions.
- The nasal-spray flu vaccine - a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for "Live Attenuated Influenza Vaccine"). LAIV is approved for use in healthy people 5 years to 49 years of age who are not pregnant.
Each vaccine contains three influenza viruses - one A (H3N2) virus, one A (H1N1) virus and one B virus. The viruses in the vaccine change each year based on international surveillance and scientists' estimations about which types and strains of viruses will circulate in a given year.
About 2 weeks after vaccination, antibodies that provide protection against influenza virus infection develop in the body.
When to get vaccinated
October or November each year is the best time to get vaccinated, but you can still get vaccinated in December and later. Flu season can begin as early as October and last as late as May.
Who should get vaccinated
In general, anyone who wants to reduce the chance of getting the flu can get vaccinated. However, certain people should get vaccinated each year. They are either people who are at high risk of having serious flu complications or people who live with or care for those at high risk for serious complications.
People who should get vaccinated each year are:
- People at high risk for complications from the flu:
- People 65 years and older;
- People who live in nursing homes and other long-term care facilities that house those with long-term illnesses;
- Adults and children 6 months and older with chronic heart or lung conditions, including asthma;
- Adults and children 6 months and older who needed regular medical care or were in a hospital during the previous year because of a metabolic disease (like diabetes), chronic kidney disease or weakened immune system (including immune system problems caused by medicines or by infection with human immunodeficiency virus [HIV/AIDS]);
- Children 6 months to 18 years of age who are on long-term aspirin therapy (Children given aspirin while they have influenza are at risk of Reye syndrome.);
- Women who will be pregnant during the influenza season;
- All children 6 to 23 months of age;
- People with any condition that can compromise respiratory function or the handling of respiratory secretions (that is, a condition that makes it hard to breathe or swallow, such as brain injury or disease, spinal cord injuries, seizure disorders or other nerve or muscle disorders.
- People 50 to 64 years of age. Because nearly one-third of people 50 to 64 years of age in the United States have one or more medical conditions that place them at increased risk for serious flu complications, vaccination is recommended for all persons aged 50 to 64 years.
- People who can transmit flu to others at high risk for complications. Any person in close contact with someone in a high-risk group (see above) should get vaccinated. This includes all health-care workers, household contacts and out-of-home caregivers of children 0 to 23 months of age and close contacts of people 65 years and older.
Use of the nasal spray flu vaccine
It should be noted that vaccination with the nasal-spray flu vaccine is always an option for healthy persons aged 5 to 49 years who are not pregnant. This vaccine is not subject to prioritization and can be given to healthy 5- to 49-year-olds at any time.
Who should not be vaccinated
There are some persons who should not be vaccinated without first consulting a physician. These include:
- Anyone who has a severe allergy to chicken eggs.
- Anyone who has had a severe reaction to an influenza vaccination in the past.
- Anyone who developed Guillain-Barré syndrome (GBS) within 6 weeks of getting an influenza vaccine previously.
- Children less than 6 months of age.
- Anyone who has a moderate or severe illness with a fever. (Wait to get vaccinated until symptoms lessen.)
The ability of flu vaccine to protect a person depends on the age and health status of the person getting the vaccine and the similarity or "match" between the virus strains in the vaccine and those in circulation. Testing has shown that both the flu shot and the nasal-spray vaccine are effective at preventing the flu.
Vaccine side effects (what to expect)
Different side effects can be associated with the flu shot and LAIV.
The flu shot: The viruses in the flu shot are killed (inactivated), so you cannot get the flu from a flu shot. Some minor side effects that could occur are:
- soreness, redness or swelling where the shot was given
- fever (low grade)
If these problems occur, they begin soon after the shot and usually last 1 to 2 days. Almost all people who receive influenza vaccine have no serious problems from it. However, on rare occasions, flu vaccination can cause serious problems, such as severe allergic reactions. As of July 1, 2005, people who think that they have been injured by the flu shot can file a claim for compensation from the National Vaccine Injury Compensation Program (VICP). For more information go to http://www.hrsa.gov/vaccinecompensation.
LAIV: The viruses in the nasal-spray vaccine are weakened and do not cause severe symptoms often associated with influenza illness. (In clinical studies, transmission of vaccine viruses to close contacts has occurred only rarely.)
In children, side effects from LAIV can include:
- runny nose
- muscle aches
In adults, side effects from LAIV can include:
- runny nose
- sore throat
Source: The Centers for Disease Control and Prevention