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Learn about the
Flu Vaccine
What is the flu?
The flu (also known as influenza) is a highly contagious respiratory infection. The flu spreads mainly via droplets made when someone with the flu coughs or sneezes. You can get the flu if you come into close contact with someone who has the virus.
Flu symptoms usually appear shortly after contracting the illness. They include:
Did you know?
You can be contagious with the flu and spread it to others before you start experiencing symptoms (similar to COVID-19). This is another reason why it is important to protect yourself and others by getting your flu shot each year.
The flu can be a serious and even fatal illness.
Each year in Canada, there are an estimated 2.5 million symptomatic cases of the flu. 1, 2 It is responsible for:
Everyone is at risk of complications from the flu. However, some are at higher risk than others.
Because of differences in immune systems and levels of exposure to the flu, some people are at higher risk of complications from the flu than others. They include:
Children under 5 years of age
Their immune system is still developing. This makes it more difficult to fight off infections.
People who are pregnant
The immune system is weakened among pregnant individuals as the baby grows.
People with underlying chronic health conditions
Conditions such as diabetes and cardiovascular disease are associated with having an increased risk of influenza related complications and infection of influenza can exacerbate these chronic conditions.
People 65 years of age and older
Because of something called "immunosenescence." This means that as we age, our immune systems weaken over time.
Residents of nursing homes or chronic care facilities
Residents are at a higher risk of exposure to the flu because of close living quarters and shared caregivers.
Indigenous peoples
There is a higher prevalence of chronic conditions among Indigenous peoples, making them at higher risk of the flu.
On top of protecting yourself, getting the flu shot is especially recommended if you are likely to pass it to a person at high risk of the flu. This includes people who:
- Share a household with a high risk person
- Are a regular childcare provider to children under the age of 5
- Are a heath care and/or care provider working in community settings
- Work in closed or relatively closed environments with people who are high risk
Are you a caregiver of an older adult?
If you or someone in your household is a primary caregiver to an older adult or often has close contact with an older adult, you should get vaccinated against the flu. You may not be at high risk of complications from the flu, but getting vaccinated lowers your chances of getting sick and passing the virus to your loved ones who may be at higher risk.
Did you know?
Around half of Canadians over 50 years old report having at least one of these conditions. This puts a significant part of the population at risk from the flu.
The flu can trigger other chronic health conditions. They can also make existing health conditions worse.
Most people who get sick from the flu recover. But for some, the flu can have broader impacts on other organs in our bodies.
Hospitalization can have long term impacts
People of any age can be hospitalized for the flu. Hospitalization and bed rest can cause other unrelated complications that accelerate the aging process (like bone loss and reduced blood volume). Being in the hospital can lead to a decline in physical and/or cognitive health, which can result in disability and a loss of independence.
In Summary
Chronic conditions increase the risk of complications from the flu. At the same time, the flu itself can trigger respiratory, cardiac, or neurological events that are unrelated to an existing chronic health condition.
Getting the flu shot is your best defense
Getting your flu shot each year is the best way to defend yourself against getting sick from the flu. It is recommended for everyone over 6 months of age.
Getting your flu shot helps:
Your immune system build protection that prevents you from getting the flu or getting very sick from the flu. This means that you also protect your loved ones and other people you come in contact with since you are less likely to spread the virus.
You become less likely to be hospitalized with the flu, as well as worsen or trigger existing health conditions. Allowing for more space for those in your community who need emergency care.
I got my flu shot last year. Why do I need to get it again this year?
The flu shot is a seasonal vaccine, meaning you should get it every year before or during flu season. Flu season happens in the fall, winter and early spring months, typically between November and March.
Two reasons you need a flu vaccine each year is because:
1. The impact of the vaccine in reducing the risk of flu decreases over time, meaning it isn’t as effective after the first season
2. The virus that causes the flu may mutate every year (known as "antigenic drift”). The flu vaccine is developed each year to adjust to these mutations.
Did you know there are many different types of flu vaccines?
Not all flu vaccines are created the same. There are many things that are considered, including:
Some vaccines are created using egg-based technologies. A chicken egg is used to replicate the virus. The antigens of the virus are extracted and purified for use in a vaccine. According to NACI, individuals who are allergic to eggs may be vaccinated against the flu using the full dose of any age-appropriate product. Speak to your health care provider for more information.
These vaccines are created by allowing the viruses to replicate in a mammalian cell culture. The viral antigen is then extracted from the culture and purified to make the vaccine.
flu vaccines
The recombinant technique uses the genetic instructions for the component included in the vaccine and ensures an exact match to the WHO’s recommended viral antigen.
Flu vaccines are developed with different strains of the flu virus. The World Health Organization (WHO) makes recommendations on which flu virus strains should be included in the flu vaccine each year.
Quadrivalent Vaccine
A quadrivalent vaccine protects against four flu strains:
- Two influenza A strains
- Two influenza B strains
Trivalent Vaccine
A trivalent vaccine protects against three flu strains:
- Two influenza A strains
- One influenza B strains
Standard Dose
Standard-dose flu vaccines are vaccines with a standard dose of the virus antigen (the part of the vaccine that helps protect you from a virus).
High-Dose
High-dose flu vaccines have four times the antigen (the part of the vaccine that helps protect you from a virus) compared to standard dose flu vaccines. This helps your body create a stronger immune response to the virus.
Adjuvanted
An adjuvanted flu vaccine has an adjuvant added to it. An adjuvant is an ingredient that is added to some vaccines and helps promote a stronger immune response.
Live-attenuated
Live attenuated vaccine is a nasal spray that is made with attenuated (weakened) live flu virus. This vaccine is not recommended for pregnant individuals, people with chronic health care conditions, and health care workers.
The flu shot is recommended by the National Advisory Committee on Immunization (NACI) for everyone over the age of 6 months, every year.
Trivalent
Standard Dose
Standard Dose (egg or cell culture based)
Quadrivalent (NACI Recommended)
Standard Dose
Trivalent
Standard Dose
Quadrivalent
Standard Dose (egg or cell culture based)
Live attenuated nasal spray*
Trivalent
Standard Dose
Quadrivalent
Standard Dose
Standard Dose Recombinant
Live attenuated nasal spray*
Trivalent
Standard Dose
Quadrivalent
Standard Dose
Standard Dose Recombinant
Live attenuated nasal spray*
Trivalent
Standard Dose
Adjuvanted Standard Dose
High Dose
Quadrivalent
Standard Dose
Standard Dose Recombinant
High Dose
*The quadrivalent live attenuated nasal spray vaccine is not recommended for children and adults with severe asthma, chronic health conditions, pregnant individuals, and health care workers
**Not all provinces and territories publicly fund the high dose vaccine. Speak to your healthcare provider to learn more.
For more information on what flu vaccines are right for you please reference the National Advisory Committee on Immunization (NACI) flu vaccine recommendations.
What is NACI?
NACI makes recommendations on the use of vaccines approved for use in Canada and advises the Public Health Agency of Canada on vaccination. This includes recommendations for groups who are especially at risk of vaccine-preventable diseases, and specific target groups for vaccination.
The flu shot is recommended by the National Advisory Committee on Immunization (NACI) for everyone over the age of 6 months, every year.
A quadrivalent vaccine is recommended for infants in this age group (if unavailable, a trivalent vaccine should be used)
Any age appropriate quadrivalent vaccine is recommended for children in this age group (if unavailable, a trivalent vaccine should be used)
However, there are some groups not recommended for the Quadrivalent live attenuated nasal spray*
Any of the available vaccines authorized for this age group should be used
However, there is evidence that the flu shot provides better efficacy than nasal spray in healthy adults
There are some groups not recommended for the Quadrivalent live attenuated nasal spray*
Any of the available vaccines authorized for this age group should be used
High-dose vaccines are recommended over standard-dose vaccines for adults aged 65 and older on an individual-level recommendation, as they provide better protection against influenza (if unavailable, any of the available vaccines authorized in this age group should be used)**
*The quadrivalent live attenuated nasal spray vaccine is not recommended for children and adults with severe asthma, chronic health conditions, pregnant individuals, and health care workers
**Not all provinces and territories publicly fund the high dose vaccine. Speak to your healthcare provider to learn more.
For more information on what flu vaccines are right for you please reference the National Advisory Committee on Immunization (NACI) flu vaccine recommendations.
What is NACI?
NACI makes recommendations on the use of vaccines approved for use in Canada and advises the Public Health Agency of Canada on vaccination. This includes recommendations for groups who are especially at risk of vaccine-preventable diseases, and specific target groups for vaccination.
What are the common reactions after the flu vaccine?
You cannot get the flu from the vaccine! Flu vaccine side effects are common but are mild and resolve within a few days. It is safer to get the flu vaccine than to get the flu. Common reactions include:
Additional Symptoms:
Where do I go to get my flu shot?
In most provinces and territories in Canada, you are able to get your flu shot at the pharmacy, local clinics in your community or from your family doctor. The best way to find out where it is easiest for you to get vaccinated is through your provincial or territorial governments website.
Publicly funded flu shots can vary between provinces and territories. Ask your health care provider about which flu vaccine is best for you
Can I get the flu shot at the same time as the COVID-19 vaccine?
Yes. According to NACI, it is safe to get the flu shot at the same time as the COVID-19 vaccine for those aged 5 years and older (provinces and territories may have varying guidance). This is an easy way to stay up to date with both vaccines!
References
1 Somes MP, Turner RM, Dwyer LJ, Newall AT. Estimating the annual attack rate of seasonal influenza among unvaccinated individuals: A systematic review and meta-analysis. Vaccine 2018 May;36(23):3199–207.
2 Statistics Canada. Population estimates on July 1st, by age and sex, 2021. https://www150.statcan.gc.ca/t1/tbl1/en /tv.action?pid=1710000501
3 Schanzer DL, Zheng H, Gilmore. BMC Infect Dis. 2011 Apr 12;11:90
4 Summary of the National Advisory Committee on Immunization (NACI) Seasonal Influenza Vaccine Statement for 2022–2023. (2022).
5 Murata, Y., et al. (2007).J Infect Dis, 195(7), 1029-1037.
6 McCullers, J. A. (2006). Clin Microbiol Rev, 19(3), 571-582.
7 Cates, C. J., et al. (2013). Cochrane Database Syst Rev(2), CD000364.
8 Kopsaftis, Z., et al. (2018). Cochrane Database Syst Rev, 6, CD002733.
9 Udell, J. A., et al. (2015). Expert Rev Cardiovasc Ther, 13(6), 593-596.
10 Kwong, J. C., et al. (2018). N Engl J Med, 378(4), 345-353.
11 Kytomaa, S., et al. (2019). JAMA Cardiol, 4(4), 363-369
12 Panhwar, M. S., et al. (2019). JACC Heart Fail, 7(2), 112-117.
13 Rezkalla, S., et al. (2010). Wisconsin Medical Journal, 109(4), 209-213.
14 Warren-Gash, C., et al. (2018). Eur Respir J, 51(3).
15 Boehme, A. K., Let al. (2018). Ann Clin Transl Neurol, 5(4), 456-463.
16 Ekstrand, J. J. (2012). Semin Pediatr Neurol, 19(3), 96-100.
17 Schaffner, W., et al. (2007). Clinical Diabetes, 25(4), 145-149.
18 Watanabe, T. (2013). Eur J Pediatr, 172(1), 15-22.
