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Flu Vaccine

Flu spreads easily. Getting vaccinated every year is the best way to protect yourself from the flu and its complications.

The vaccine allows the body to produce antibodies to fight the flu. However, studies show that the number of antibodies can decrease in the year after vaccination. This reduction particularly affects young children, seniors 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 you get vaccinated each year in order to protect yourself from flu complications. Consult the details of the Flu Vaccination Program to know how to proceed and where to get vaccinated.

Description of Vaccine

In Quebec, the vaccine is available in 2 forms:

Vaccine Safety

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 Quebec 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 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 60 and over and those with chronic illnesses, the vaccine especially help reduce the risks of complications from the flu, hospitalisation and death.

Vaccinating Children

It is important to vaccinate children so that they may be protected against the flu and its complications. If your child does not feel well the day of the vaccination, see the Conditions for Postponing Vaccination section to know if you must delay their vaccine.

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 less than 6 months may also catch the flu. In addition, they are part of the people most at risk for presenting complications. It is therefore important that all people around children less than 6 months old be vaccinated to avoid transmitting the flu to them.

If you have a child that is less than 6 months old, you and the people around you can receive the vaccine for free 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 very important that children less than 9 years old getting the flu vaccine for the first time receive the two 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.

People 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.

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.

Symptoms after Vaccination

Some reactions may occur following vaccination:

Last update: November 25, 2015 9:58 AM

The information on this website by no means replaces the advice of a health professional. If you have questions regarding your health, contact Info-Santé 8-1-1 or see a health professional.

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