Inactivated Influenza Vaccine

Search Knowledgebase

Topic Contents

Inactivated Influenza Vaccine


Generic NameBrand Name
trivalent inactivated influenza vaccine (TIV)Fluviral, Fluzone, Vaxigrip
live attenuated influenza vaccineFluMist (nasal)

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.

A new flu vaccine (FluMist) that is given as a spray in the nose may be available in Canada for the 2010–2011 flu season. Because this flu vaccine uses live flu virus, it is not recommended for children younger than 2 years, pregnant women, or people with some health conditions. For more information, talk with your doctor.

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 vaccine 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 vaccine once a year. But a yearly flu vaccine is especially important for certain people who are more likely to have complications from the flu.1

Flu vaccines for children, teens, and adults

Canada's National Advisory Committee on Immunization (NACI) recommends that everyone 6 months old and older should get a flu vaccine. The vaccine is especially important for people who are at higher risk of problems from the flu, including:2, 3

  • People who are age 65 or older. People age 65 or older are the most likely to have problems from the flu.
  • Adults and children who have long-term health problems or an impaired immune system.
  • People who live in nursing homes or long-term care centres.
  • People who have a weak immune system.
  • Women who will be pregnant during the flu season.
  • Children 6 to 23 months of age.
  • Children who are 24 months to 18 years old who use long-term ASA treatment.
  • People who are obese with a body mass index (BMI) of 40 or more.
  • First Nations peoples.
  • Healthy children ages 2 to 4 years old.

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 vaccine.

You can keep track of when your child received vaccines using the National Childhood Immunization Record (What is a PDF document?), the Alberta childhood immunization record (What is a PDF document?), or the British Columbia Childhood Immunization Record (What is a PDF document?).

For the latest updates on influenza immunization policy issues, see the NACI recommendations on the Health Canada website at

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 immunized each year with the flu vaccine. 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.4

How Well It Works

How well the flu vaccine 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.4 But 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.4

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.4 Another study found that the vaccine was effective in preventing the flu in 56% of children between ages 3 to 9.4 These rates may be lower in children with certain health conditions, such as asthma. But, 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.4

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.5

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.4 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 vaccine every October or November. In case of a shortage, the NACI recommends that the following people have first priority for receiving the flu vaccine: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

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. National Advisory Committee on Immunization (NACI) (2009). Statement on influenza vaccination for the 2009–2010 season. Canada Communicable Disease Report, 35(ACS-6): 1–41. Also available online:
  2. National Advisory Committee on Immunization (NACI) (2010). Statement on seasonal trivalent inactivated influenza vaccine (TIV) for 2010–2011. Canada Communicable Disease Report, 36(ACS-6): 1–49. Also available online:
  3. National Advisory Committee on Immunization (NACI) (2006). Canadian Immunization Guide, 7th ed., pp. 1–372. Ottawa: Public Health Agency of Canada. Also available online:
  4. Centers for Disease Control and Prevention (2004). Prevention and control of influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR, 53(RR-6): 1–44. Also available online: [Erratum: (2004). MMWR, 53(RR-6): 743. Also available online:]
  5. Ressel GW (2003). ACIP releases 2003 guidelines on the prevention and control of influenza. American Family Physician, 68(7): 1425–1433.


By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Primary Medical Reviewer Brian D. O'Brien, MD - Internal Medicine
Specialist Medical Reviewer Christine Hahn, MD - Epidemiology
Last Revised August 24, 2011

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.