Flu spreads easily. People who are more at risk of being hospitalized after the flu should get vaccinated every year. For these people, vaccination is the best protection against the flu and its complications.
Vaccination allows the body to make antibodies to fight the flu. However, studies have shown that the number of antibodies may decrease in the year after vaccination. This decrease particularly affects older adults and people with a weakened immune system.
In addition, viruses that cause flu constantly change. The composition of flu vaccines are reviewed annually in order to include the virus strains most likely to be in circulation during the flu season.
For these reasons, it is highly recommended that people most at risk of developing complications get vaccinated each year in order to protect themselves. Consult the details of the Flu Vaccination Program to know how to proceed and where to get vaccinated.
Where to get Vaccinated
For information on the Flu Vaccination Campaign for each region of Québec, see the Where to get vaccinated section.
Description of Vaccine
Flu vaccine is safe. It cannot transmit flu or other illnesses. In fact, the viruses or a part of the viruses that it contains are killed or too weak to reproduce and cause the flu.
In Canada and at the World Health Organization (WHO), there are several vaccination surveillance programs. These programs ensure, among other things, the quality of vaccines offered. Among these is the Québec surveillance program, ‘Effets secondaires possiblement reliés à l’immunisation’ (ESPRI). This program was established in 1990 by the Ministère de la Santé et des Services sociaux.
Effectiveness of Vaccine
The flu vaccine generally takes 2 weeks before being fully effective.
The protection offered by the vaccine may vary from person to person, but it lasts at least 6 months.
You must also be aware that the vaccine protects only against strains of the flu virus that it contains. It does not protect against other respiratory infections such as the cold. Flu is often confused with cold. To learn more, go to the Differences between Flu and Cold page.
Factors that Determine Effectiveness
The vaccine’s effectiveness depends on the following:
- The age of the person vaccinated
- The state of the person’s immune system, meaning the system that allows their body to defend itself against infections
- The degree of kinship between the virus strains circulating and those contained in the vaccine
The vaccine therefore does not offer 100% protection against the flu. The vaccine prevents the flu in about 40 to 60% of healthy people when the strains of viruses it contains correspond to strains circulating.
In exceptional circumstances, it can happen that the strains of viruses included in the vaccine are different from the ones circulating. Indeed, the virus can evolve differently from what was predicted, and therefore be less effective. Nonetheless, the annual flu vaccine is still recommended.
For people aged 75 and over and those with chronic illnesses, the vaccine especially help reduce the risks of complications from the flu, hospitalisation and death.
Vaccination is recommended for children who have certain chronic diseases, members of the same household and informal caregivers of children under 6 months of age to ensure they are effectively protected against the flu and its complications. If vaccination is recommended for your child and he does not feel well enough on the day of vaccination, go to the Conditions for Postponing Vaccination section to find out whether or not you need to postpone his vaccination.
Here is some information on vaccinating children according to their age:
Children Less than 6 Months Old
It is not recommended to vaccinate children aged less than 6 months. Indeed, the effectiveness of the vaccine has yet to be proven for children that age. The vaccine is therefore not offered to them.
However, children under 6 months of age can also catch the flu. Furthermore, they are among those who are more at risk of being hospitalized after the flu. Therefore, vaccination is recommended for members of the same household and informal caregivers of children under 6 months of age to avoid passing on the flu to them.
If you are a member of the same household or the informal caregivers of a child under 6 months of age, you can get vaccinated free of charge under the Flu Vaccination Program.
Children Less than 9 Years Old
Children less than 9 years old getting the flu vaccine for the first time must receive 2 doses of vaccine. The second dose must be given a month after the first. Parents must therefore plan 2 appointments to get their child a flu vaccination.
Indeed, as most vaccines given in childhood, the first injection of the flu vaccine must be followed by a booster dose. The first dose of the vaccine allows the child’s immune system to, in a way, ‘get acquainted with the virus’ and to fight it, but for only a few weeks. The second dose allows the child’s immune system to produce more antibodies to fight the virus on a longer term.
It is therefore important that children less than 9 years old getting the flu vaccine for the first time receive the 2 doses of vaccine. The second dose will allow them to be best protected during the entire flu season.
This procedure also applies to children who received the vaccine against pandemic (H1N1) 2009 flu virus. These children should receive 2 doses of the vaccine if they are getting a flu vaccine for the first time.
Only children less than 9 years old who have already received the flu vaccine need to receive a single dose of it.
Children from 6 to 23 months old and those who have certain chronic diseases can get vaccinated free of charge under the Flu Vaccination Program.
Children Aged 9 and Up
From the age of 9, children that get the flu vaccine receive a single dose of it, even if they have never received a flu vaccine before.
The immune system of a 9 year old child is indeed sufficiently developed to produce enough antibodies to protect them with a single dose of the vaccine.
Children who have certain chronic diseases can get vaccinated free of charge under the Flu Vaccination Program.
Conditions for Postponing Vaccination
There are very few reasons for delaying getting a vaccine.
As such, people with a cold can get vaccinated with no problem. If a person to receive an intranasal vaccine has too much nasal discharge, it is possible for them to get an injectable vaccine.
Only a serious illness can cause a vaccinator to delay a vaccine after evaluating the general condition of the person to be vaccinated. The fact of having a fever is not the only indication of a serious illness.
Last update: October 25, 2018