Inactivated influenza vaccine
Examples
Generic Name Brand Name trivalent inactivated influenza vaccine (TIV) Fluviral, Fluzone, Vaxigrip How It Works
Influenza (flu), a contagious viral disease, can usually be prevented by getting immunized with a flu vaccine. The inactivated influenza vaccine, known as the "flu shot," contains three different strains of killed influenza viruses that are most likely to be circulating within the population in a given year. This vaccine is injected into a muscle, usually in the upper arm. The body develops antibodies to fight off the similar strains of influenza within about 2 weeks.
The vaccine is reformulated every year because the influenza viruses change in ways that make a previous year's vaccine ineffective. In Canada, the United States, and other temperate areas of the northern hemisphere, flu epidemics usually occur in the winter. To be fully protected, you need to be immunized each year, ideally in October or November.
Why It Is Used
The flu shot helps protect people from developing influenza infection and its possible complications. In Canada, the National Advisory Committee on Immunization (NACI) suggests that everyone older than 6 months of age get a flu shot once a year. But a yearly flu shot is especially important for certain people who are more likely to have complications from the flu.1
Flu shots for children and teens
The NACI suggests that everyone older than 6 months of age get a flu shot once a year. But a yearly flu shot is especially important for all children between the ages of 6 months and 23 months because of their increased risk for complications from the flu. Vaccination with the flu shot is part of the routine immunization schedule. Household contacts and caregivers of children between 0 and 23 months of age should also be vaccinated with the flu shot.
The flu shot is also recommended for children age 24 months and older and teens with certain health conditions. This includes children who:
- Have long-term heart or lung conditions, such as asthma or a congenital heart defect.
- Have health conditions that have required regular medical follow-up or hospitalization within the last year. These conditions include diabetes and other chronic metabolic diseases; kidney problems; blood diseases, such as sickle cell disease; or immune system problems, including human immunodeficiency virus (HIV) or those that are caused by medication.
- Are taking ASA for a long-term medical condition. These children are at greater risk for developing Reye's syndrome if they become infected with influenza.
Yearly vaccination is recommended for caregivers and close contacts of these children.
You can keep track of when your child received vaccines using the national childhood immunization record
(What is a PDF document?) or the British Columbia childhood immunization record
Influenza vaccines in Canada contain only trace amounts of thimerosal (a compound containing mercury), if any at all. In response to public concern, vaccine manufacturers in Canada are working to develop thimerosal-free flu vaccines.2 If you have concerns regarding thimerosal in vaccines, talk to your doctor.
For the latest updates on influenza immunization policy issues for young children, see the NACI recommendations on the Health Canada Web site at www.hc-sc.gc.ca/dc-ma/influenza/index_e.html.
Flu shots for adults
The NACI suggests that everyone over 6 months of age have a flu shot once a year. But a yearly flu shot is especially important for adults who have a high risk for getting serious health problems (complications) from the flu. These adults are those who:1
- Are 65 years of age or older.
- Live in a long-term care centre, such as a nursing home, or any facility that houses people of any age with chronic medical conditions.
- Have a long-term heart or lung condition, such as asthma or coronary artery disease.
- Have a health condition that has required regular medical follow-up or hospitalization within the last year. These conditions include diabetes and other chronic metabolic diseases; kidney problems; blood diseases, such as sickle cell disease; or immune system problems, including human immunodeficiency virus (HIV) or those that are caused by medication.
- Will be pregnant or breast-feeding during the flu season and have any of the above health conditions, or will be in close contact with people who are considered high risk for complications from the flu. The inactivated influenza vaccine is safe for pregnant women, including those who are in their first trimester.3 Pregnant women who will have their baby during flu season should receive their immunizations during their third trimester; otherwise, they may expose their baby to the flu virus. Also, it is safe for babies to breast-feed after their mothers have been immunized with the vaccine.
People in a high-risk group travelling to the southern hemisphere from April to September (flu season in that hemisphere) or travelling to the tropics or with organized groups at any time of year should review their vaccination records to determine whether they should get a flu shot.
Close contacts of people in high-risk groups
Close contacts (such as health care workers, family members, and daycare providers) of people who are at high risk for complications of the flu should also be vaccinated each year with the flu shot.1 This includes those times that the high-risk person has a severely impaired immune system and is in a protected environment. A protected environment often means the person is hospitalized in an isolated room where staff take extra care to prevent the spread of germs.3
How Well It Works
How well the flu shot works to prevent influenza in part depends on how close the viruses in the vaccine match the flu viruses circulating in the population. A person's age and the body's ability to develop sufficient antibodies also influence the effectiveness of the vaccine.
When the vaccine contains viruses similar to those circulating in the population, it is effective in preventing the flu in approximately 70% to 90% of adults younger than 65. Protection is less in people age 65 and older.3 However, the vaccine is still important for preventing severe illness, complications and death from the flu virus. For example, among adults age 65 and older who live in long-term care facilities, the flu vaccine is about 30% to 40% effective in preventing influenza, but about 50% to 60% effective in preventing hospitalization or pneumonia and 80% effective in preventing death from complications.3
The inactivated flu vaccine's effectiveness for preventing the flu in children varies widely. One study of children between 1 and 15 years of age showed the inactivated flu vaccine to be 77% to 79% effective in preventing the flu.3 Another study found that the vaccine was effective in preventing the flu in 56% of children between ages 3 to 9.3 These rates may be lower in children with certain health conditions, such as asthma. However, as in older adults and people with health problems, the vaccine is important in protecting children from complications of the flu. If symptoms of influenza develop despite getting immunized, they usually are milder.
Side Effects
Serious side effects from the inactivated flu vaccine are extremely rare. The most frequent side effect is mild soreness where the injection is given, usually in the upper arm. The soreness is rarely severe enough to interfere with daily activities.3
Because the inactivated flu vaccine contains killed viruses, it cannot cause influenza. Sometimes a slight fever, muscle aches or pains, and a general feeling of illness develop within about 6 to 12 hours after receiving the immunization and last about 1 or 2 days. These side effects most often occur in young children who have had little to no prior exposure to the flu or the vaccine and have not yet developed antibodies. The side effects are also more likely to occur in people with immune system disorders.
People with a severe allergy to eggs, chicken, or any other part of the vaccine should not receive the vaccine without first talking with a health professional.1
See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)
What To Think About
Who should not get a flu shot
Some people who are at high risk for complications from the flu cannot get a flu shot because they have a severe allergy to eggs or chicken. These people may benefit from taking an antiviral medication.
Anyone who has a high fever should not be given the vaccine. The vaccine can still be given if an otherwise healthy person has a minor illness, such as a cold.4
It is not known whether the flu shot can increase the risk for recurrence of Guillain-Barré syndrome (GBS) in people with a history of the disease. Usually, the flu shot is only recommended for these people if they are at high risk for severe complications of the flu.3 If you have had GBS, talk to your health professional before getting vaccinated.
If you are not high risk for having complications from the flu, you may have to pay for the flu shot.
Priority immunization
Ideally, you should receive a flu shot every October or November. In case of a shortage, the NACI recommends that the following people have first priority for receiving the flu shot:1
- People who are age 65 and older
- People between the ages of 2 and 64 who have medical conditions that increase their risk for influenza-related complications
- Young children between the ages of 6 months and 23 months
- Health care workers who have direct contact with patients
- People who live in long-term care facilities
- Household contacts and out-of-home caregivers of children younger than 6 months of age
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Related Information
| Author: | Sydney Youngerman-Cole, RN, BSN, RNC | Last Updated: September 22, 2006 |
| Medical Review: | Adam Husney, MD - Family Medicine W. David Colby IV, MSc, MD, FRCPC - Infectious Disease | |
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| Topic Contents | |
| Examples | |
| How It Works | |
| Why It Is Used | |
| How Well It Works | |
| Side Effects | |
| What To Think About | |
| Related Information | |
| References | |