Influenza Vaccine Q&A



How well does influenza vaccine protect against influenza?

Protection from the vaccine develops about one to two weeks after the shot, and may last up to one year. The vaccine is about 70 to 90 per cent effective in preventing influenza infection in healthy adults. In children, it is about 80 to 90 per cent effective in preventing influenza infection, and about 62 to 73 per cent effective in preventing illness with fever. In elderly people, the vaccine can prevent pneumonia and hospitalization in about six out of ten people, and prevent death in about eight out of ten people.

Who should get the influenza vaccine?

The vaccine is especially important for people in high-priority groups. These groups include people who are at high risk of complications from influenza and people who are most likely to spread the virus to the high-risk population. The high-priority groups include:
  • Healthy children 6 to 23 months of age
  • Anyone aged 65 or older
  • Anyone aged 6 months and older with chronic heart or lung disease that requires medical or hospital care
  • Anyone aged 6 months and older with chronic conditions such as diabetes or other metabolic diseases, cancer, kidney disease, blood disorders or weakened immune system
  • Anyone who lives, works or volunteers in a nursing home, long-term care facility, chronic care facility, retirement home, hospital, or other healthcare setting
  • Anyone aged 6 months and older who lives in the same household or is in contact with people at high risk of influenza complications
  • Anyone aged 6 months to 18 years who has been treated for long periods with aspirin (acetylsalicylic acid)
  • Anyone who provides home care to people at high risk
  • Pregnant women
  • Emergency response workers (i.e., ambulance staff, fire fighters, police) and other essential service providers
  • Anyone providing regular child care to children aged 0 to 23 months, whether in or out of the house
  • Anyone providing services to people at high risk within closed or relatively closed settings (e.g., crews on ships)
  • Anyone 6 months of age and older at high risk of complications traveling to areas of the world where the influenza virus is circulating
  • Anyone in direct contact with live poultry and/or involved in the slaughtering process is recommended to get a flu shot

Who should NOT get the influenza vaccine?
The following persons should not get the influenza vaccine:
  • Infants under six months of age (the current vaccine is not recommended for this age group)
  • Anyone with a serious allergy (anaphylaxis to eggs or egg products). A serious allergic reaction usually means that the person develops hives, swelling of the mouth and throat or trouble breathing after eating eggs or egg products
  • Anyone who has a severe allergy to any component of the vaccine. Two influenza vaccines will be distributed through Ontario's universal influenza immunization program this season; Vaxigrip® (produced by Aventis Pasteur) and Fluviral® (produced by Shire Biologics). Both vaccines may contain trace amounts of Thimerosal (a preservative) and formaldehyde. In addition, Vaxigrip® may contain traces of the antibiotic neomycin. Please check with your physician or other health care provider to make sure that you do not have a severe allergy to any component of the vaccine that you will be getting
  • Anyone who had a serious allergic reaction to a previous dose of the influenza vaccine

Also:
  • People with a history of Guillain-Barré Syndrome should consult their physician before getting the vaccine
  • People who are acutely ill with a fever at the time that the shot is being given should usually wait until they recover before getting the influenza vaccine
  • People who developed Oculo-Respiratory Syndrome (ORS) after getting an Influenza Shot in a previous season should advise their doctor that they had ORS. Medical professionals should refer to the decision-making flow chart for influenza immunization of people with ORS following previous influenza immunization


What are the risks from influenza vaccine? The influenza vaccine, like any medicine, is capable of causing side effects, which can be either mild or, in few cases, severe. The risk of the vaccine causing serious harm is extremely small. Almost all people who get the influenza vaccine have no serious problems. Most people who get the vaccine have either no side effects, or mild side effects such as soreness, redness or swelling where the shot was given. A small number of people may get a fever or muscle aches which start shortly after getting the influenza shot, and last about one to two days.