Things you want to know about the FLU SHOT this winter 2019-2020

A lot of advocacy is going on about the flu shot right now. Lulu and I wanted to write an article that goes into a little more detail about the rationale behind the things you probably have heard about. We also want to address the confusing things that you might have heard about standard-dose versus high-dose flu shots.

Hopefully we will be able to provide you with additional information, or at least give you something to talk about when someone talks to you about the flu shot.

Where can I receive the flu shot?

Commonly you can get the flu shot from community pharmacies (for anyone who is 5 years and older) and from your doctor’s office. It’s free of charge with Ontario Health Card.

What are the kinds of flu shots that are available this year?

In the previous year, there were 3 types of vaccines commonly available: a nasal spray vaccine for young children who did not want to receive an injection, a standard-dose flu shot that you typically get at the pharmacy, and a high-dose flu shot for seniors 65 years and older.

For this flu season, the nasal spray is not available for children, and only the standard-dose and high-dose flu shot injections are available. Pharmacies only administer standard-dose flu shot. High-dose flu shots are available at the doctor’s office.

Why are there two types of flu shots? Why are high-dose flu shots reserved for the elderly?

To start, there are two types of influenza viruses that are most likely to cause flu epidemics, they are influenza A and influenza B viruses. Keep this in mind.

Pharmacies administer “quadri-valent” vaccine this year, meaning that it protects against 4 strains of influenza viruses, which includes 2 strains of influenza A and 2 strains of influenza B at a standard dose. The reason why this vaccine is given to younger populations is the fact that younger people, especially children, are more likely to become severely ill with influenza B (1). The vaccine is at standard-dose reflects the fact that younger populations typically have a well developed immune system that can generate a sufficient response to the vaccine at that standard dosage.

The high-dose flu shot is available at the doctor’s office and is reserved for seniors. This vaccine is ‘tri-valent’, meaning that it covers 2 strains of influenza A and only 1 strain of influenza B, but at a dosage 4 times higher than the standard dose (1,2). The rationale behind having this vaccine is because seniors tend to be more severely affected by influenza A (2). The rationale behind the higher dose is that because seniors have a weaker immune system, these people may not develop a sufficient immune response to a standard-dose of vaccine (1). By using a much higher dose, the vaccine can generate around 23% better effectiveness than its standard dose (2).

As a caveat though, there are NO studies directly comparing the effectiveness of high-dose, trivalent flu shot to standard-dose, quadrivalent flu shot among seniors, so there is no clinical conclusion in terms of which one works better (2). (ie: is covering more strains at a standard dose compared to covering less strains at a higher dose better, the same or worse?)

In my own opinion, considering the senior population already has weakened immune system due to age, as well as the burden of influenza A viruses, especially influenza A (H3N2) in this population, the high-dose vaccine would logically confer more protection against influenza A viruses in this population (2). But if they have trouble getting the high-dose flu shots in time, then I am happy to administer the standard-dose flu shots in my pharmacy as at least they still receive some protection.

Can flu shot make me sick?

Every article written will say that the flu shot cannot give you flu. This is very true, but why is it true?

Vaccines contains pieces of a virus. The vaccine is produced by taking the influenza virus and killing it through the use of heat or chemical(3). Then the virus is completely broken down through the use of a ‘detergent’ that dissolves the virus into just floating pieces of protein. As a result the pieces of virus in the vaccine does not resemble the complete virus at all. The pieces cannot somehow become ‘reactivated’ and give you the flu.

The vaccine is technically more of a serum containing proteins that once belonged to a virus, rather than a serum with the flu virus within it.

What are the side effects of flu shot?

Commonly the site where the flu shot is given may become sore after the injection, but this is common for any intramuscular injection. You may feel sore, or achy and you may feel symptoms similar to the flu. However these symptoms are there because it is your immune system responding to the vaccine. It is your body testing its defensive capabilities in anticipation to the actual flu.

I got the ‘flu’ last year, and it was not a big deal. I’ll take a couple of days off if I get the flu, no need for the vaccine.

If you were able to go to work or go about your daily activities, it was probably not the flu that you got. Getting the flu can debilitate you especially if you belong to the “high risk population” (see details at the bottom (4)). The flu also lasts up to 3 weeks, which is much longer than a cold. The flu is also associated with high fever, severe aches, extreme fatigue, and more severe medical complications, such as pneumonia. The sheer loss in productivity, whether it be at work or with any activity with the flu is very significant.


- You can receive your flu shot free of charge at most community pharmacies if you have a valid Ontario Health Card.

- Trained pharmacists are allowed to administer flu shots to anyone who is 5 years of age and older. If you have younger children, you should bring them to the doctor.

- Children 8 years of age and under require TWO doses of flu shots at least 4 weeks apart, if they have never received flu shot previously.

- Seniors can receive the inactive, high-dose, trivalent flu shot from the doctor. If they are unable to receive it in time, they can still receive the inactive, standard-dose, quadrivalent flu shot from community pharmacies.

NACI Recommendation for Groups for whom influenza vaccination is particularly recommended (4)

1. Individuals at high risk of influenza-related complications or who are more likely to require hospitalization:

- All pregnant women

- People who are residents of nursing homes or other chronic care facilities

- People ≥ 65 years of age

- All children 6 to 59 months of age

- Indigenous peoples

- Adults or children 6 months of age and over with chronic health conditions as follows:

  • cardiac or pulmonary disorders

  • diabetes mellitus or other metabolic disease

  • cancer

  • conditions or taking medication which compromise the immune system (due to underlying disease, therapy or both)

  • renal disease

  • anemia or hemoglobinopathy

  • neurologic or neurodevelopmental conditions

  • morbid obesity (body mass index of ≥ 40)

  • children and adolescents (6 months to 18 years) undergoing treatment with acetylsalicylic acid for long periods

2. Individuals capable of transmitting influenza to those listed in #1 and/or to infants under 6 months of age:

  • Health care workers and other care providers in facilities and community settings

  • Household contacts (adults and children) of individuals at high risk of influenza related complications

  • Persons who provide care to children ≤ 59 months of age

  • Those who provide services within a closed or relatively closed setting to persons at high risk (e.g., crew on a ship)

3. Swine and poultry industry workers.


  1. Canadian Immunization Guide Chapter on Influenza and Statement on Seasonal Influenza Vaccine for 2019–2020. An Advisory Committee Statement (ACS) National Advisory Committee on Immunization (NACI).

  2. Public Health Ontario, Influenza Vaccines for the 2019–20 Influenza Season - Focus on Adults 65 Years of Age and Over.

  3. Wong, S and Webby, R. (2013). Traditional and New Influenza Vaccines. Clinical Microbiology Reviews. 26: 476 - 492.

  4. 2019/2020 Universal Influenza Immunization Program (UIIP), Ministry of Health and Long Term Care. accessed on Oct 21, 2019.

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