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Vaccinations for youth and adults 12+

Get Boosted: Information About Boosters

As we continue to learn more about COVID-19 vaccines (e.g., how long protection lasts) and the virus itself, recommendations about boosters will continue to change.  

What we know so far is that the protection (immunity) we get from COVID-19 vaccines decreases over time, as does the natural immunity you get from being infected. Having decreasing immunity, at the same time the virus continues to spread widely in our communities and restrictions that protected us from COVID-19 have been removed, means it is even more important to stay up to date with all recommended COVID-19 vaccinations, including boosters. All people in Simcoe Muskoka who are eligible for a booster are strongly encouraged to get one as soon as possible. Getting your booster will:

  • Provide good protection from infection and the risk of having long-term symptoms (Long COVID) if you do get COVID-19.
  • Provide very good protection from getting seriously sick and being hospitalized, especially for those who are more vulnerable.
  • Help stop the virus from spreading.
  • Protect our health care system from being overwhelmed.

​Adults 18+:

  • Three months (84 days) after completing your primary series (for most people that means their second dose).

Youth 12 to 17:

  • Six months (168 days) after completing your primary series.

In addition to the populations identified in the sections below, additional boosters continue to be provided to other vulnerable populations including residents of long-term care homes, retirement homes, First Nation elder care lodges and older adults in other congregate care settings that provide assisted-living and health services. Additional booster doses are offered to these populations at least three months (84 days) after the previous dose.

Adults 60+:

Recommended interval of five months (140 days) after your first booster. The minimum interval is three months (84 days).

18+ First Nation, Metis, Inuit people and household members:

You may choose to be offered a second booster at a recommended five months (140 days) after the first booster based on consideration with a health care provider of their individual risk. The minimum interval is three months (84 days).

Adults 18+:

It is recommended that you wait three months after symptom onset or positive test (if asymptomatic) before receiving your first or second booster dose.

Youth 12 to 17:

It is recommended that you wait three months after symptom onset or positive test (if asymptomatic) before getting your booster, provided it is at least 6 months (168 days) from completing your primary series (first and second dose).

Adults 18+:

  • It is recommended that you wait three months (84 days) after completion of your three-dose primary series.

Youth 12 to 17:

  • It is recommended that you wait six months (168 day) after completion of your three- dose primary series.

If you are 12+ and had a three-dose primary series but are not receiving treatment, you are eligible for an additional booster.

To complete your primary series, you must first get one dose of a Health Canada approved vaccine.

Adults 18+:

  • It is recommended that you wait three months (84 days) after completion of your primary series.

Youth 12 to 17:

  • It is recommended that you wait six months (168 days) after completion of your primary series.

Boosters are available across Simcoe Muskoka at community walk-in and pop-up clinics, appointment-based clinics, pharmacies, and some primary care providers.

Special note for people eligible for their fourth dose.

The GO-VAXX mobile clinics and the COVID-19 Immunization Clinic at 29 Sperling Drive in Barrie are offering walk-in appointments for both three- and five-month intervals. Individuals may also book appointments at these locations at the five-month interval through the provincial booking system.  To book an appointment at the three-month interval, eligible individuals must call the Provincial Vaccine Contact Centre at 1-833-943-3900. Health unit community walk-in and pop-up clinics remain walk-in only and will offer a fourth dose at both the three- and five-month interval.


If you or a family member are at increased risk for severe illness, it is even more important that everyone around you use as many layers of protection to prevent the spread of COVID-19. This includes staying up to date with all recommended COVID-19 vaccines doses, including any boosters dose(s) when eligible.

For individuals who are at increased risk, booster dose(s) add even more protection from becoming severely ill or hospitalized. Those with increased risk of getting very sick include:

  • People 50 years of age and older (the risk for severe illness increases with age).
  • People with medical conditions like a compromised immune system and/or other underlying medical conditions (risk increases with the number of conditions).
  • People who are pregnant or were recently pregnant (risk of complications that can affect the pregnancy and developing baby and increases if other risk conditions are present (e.g., underlying conditions, older age, racial inequities).
  • People living with social and structural inequities including First Nations, Inuit and Metis, people of colour, newcomers, people living with low income, and those who are underhoused or homeless (some of the inequities that put people in these groups at increased risk of getting sick and dying from COVID-19 include discrimination, inequitable healthcare access and use, educational, employment, income and housing inequities).

If a booster is needed, does that mean that vaccines don’t work?
Although some protection from serious illness and hospitalization remains after receiving a primary series of COVID-19 vaccine, protection does wane over time and so boosters are needed to increase immunity from infection (and long COVID), and to provide even more protection from serious illness, hospitalization and death.

Why are boosters recommended?
The protection you get from COVID-19 vaccines and from having a previous COVID-19 infection decreases over time. In addition to decreasing immunity, the wide spread of highly contagious variants increases the need for additional protection against COVID-19.

What are the factors that may decrease the effectiveness of the vaccine?

  • Older people and those who are immunocompromised can have a lower immune response from their primary vaccination doses.
  • A shorted interval between doses can decrease how long immunity stays high.
  • mRNA vaccines produce a stronger immune response giving better protection compared to other types of vaccines.
  • The currently spreading variants of COVID-19 are even more contagious and can cause infection and reinfection even after vaccination or previous COVID-19 illness.

What vaccine can I get for my booster?

An mRNA vaccine (Pfizer or Moderna) is recommended for a booster due to the strong protection it offers and evidence of their safety. For people 70+, Moderna is preferred as current evidence shows it produces a better immune response. In some cases, when an mRNA vaccine is not recommended or an individual prefers a different kind of vaccine, a non-mRNA vaccine can be provided as a booster with informed consent on request (see special request for non-mRNA vaccine below).

As recommend by the National Advisory Committee on Immunization (NACI), mRNA vaccines can be used interchangeably, and individuals are encouraged to get whichever vaccine is available at the time of vaccination. This is because both mRNA vaccines protect against the Omicron variant, and waiting for a preferred vaccine could put a person and their family’s health at risk. Moderna Spikevax (100 mcg) induces somewhat higher antibody levels compared to Pfizer-BioNTech Comirnaty (30 mcg). Protection against infection and severe disease from a primary series (dose one and two) with Moderna Spikevax (100 mcg) may be more durable than Pfizer-BioNTech Comirnaty (30 mcg).

Combining vaccines from different manufacturers is not a new concept. This occurs when vaccine supply or public health programs change. Different vaccine products have been used to complete a vaccine series for influenza, hepatitis A and others.

For people under the age of 30, the Pfizer-BioNTech Comirnaty vaccine will continue to be offered based on the NACI recommendation for Pfizer-BioNTech Comirnaty for this age group to further minimize the rare risk of adolescents and young adults experiencing myocarditis and/or pericarditis.

Ready to get boosted?

Getting a First and Second Dose (primary series)

Only vaccines that Health Canada has approved are being used in Ontario.

Health Canada has one of the most careful vaccine review systems in the world. A vaccine is only approved if it is safe, it works, it meets manufacturing standards, and the benefits of being vaccinated outweigh the risks of getting the disease. Canada’s best independent scientists reviewed all the data before approving the COVID-19 vaccines for Canadians. For more information see Health Canada’s vaccine development and approval infographic.

What about side effects?

Like other medications and vaccines, COVID-19 vaccines can cause side effects, but they are usually short-lived and mild.  

Side effects are the result of your immune system building protection. Once your immune system has been primed with the first dose there is a much stronger immune response to the second dose. This is a good thing and is also the reason why side effects are more likely to happen after a second dose of the vaccine.

None of the approved vaccines contain the actual COVID-19 virus, so you can't get COVID-19 from the vaccine.

The most common side effects are soreness at the injection site on your arm, tiredness, chills and/or a mild headache as the vaccine starts to work.

Serious side effects are rare. If they do happen they are usually felt minutes to hours after receiving the vaccine. Seek immediate medical attention or call 9-1-1 if you experience any of the following within three days of immunization:

  • hives
  • swelling of the face, mouth, or throat
  • trouble breathing
  • very pale colour and serious drowsiness
  • high fever (over 40C)
  • convulsions or seizures
  • other serious symptoms (e.g., “pins and needles” or numbness)

Still have questions about the COVID-19 vaccine?

Speak with your health care provider.  The province’s website has more information about vaccine safety and the COVID-19 vaccine approval process. Public Health Ontario is responsible for gathering and publicly reporting information about adverse events following immunization which can be found here.

Getting the COVID-19 vaccine remains the best defence against COVID-19 as it reduces the risk of infection, long-term complications (long COVID), and the risk of getting seriously sick or being hospitalized due to COVID-19 infection

Hospitalization and death

To understand the impact and important protection that COVID-19 vaccines have provided to people we can look at Ontario hospitalization and death outcomes by vaccination status.  

A report highlights the following (see link to report below):

  • Since vaccines have been available, unvaccinated people of all ages were more likely to be hospitalized compared to people of the same age who completed a primary vaccine series, and those who have had a primary series and a booster.

Although your body would have developed immunity from having a COVID-19 infection, we have learned that this immunity also wanes over time. Even if you have already had a COVID-19 infection, getting vaccinated can help enhance your immune response that can protect you from getting sick again. Staying up to date with all recommended doses of vaccine, including boosters is important.

Suggested intervals between infection and vaccination for youth and adults 12+:

  • If you were infected prior to getting any COVID-19 vaccination or before the completion of your primary series, it is recommended you wait four to eight weeks after symptoms onset or a positive test, before getting the vaccination, or next dose.  

For youth 12 to 17

  • Pfizer- BioNTech Comirnaty - recommended for ages 12 to 17 to minimize myocarditis risk (two doses with eight weeks in between).
  • Moderna Spikevax - with informed consent.


For adults 18+

  • Pfizer BioNTech Comirnaty - recommended for ages 12 to 29 to minimize myocarditis risk (two doses with eight weeks in between).
  • Moderna Spikevax - recommended for ages 29 and over (two doses with eight weeks in between)

For adults 18+:

  • Janssen (Johnson & Johnson) - one dose only
  • AstraZeneca Vaxzevria - two doses with at least eight weeks in between
  • Novavax Nuvaxovid - two doses with eight weeks in between


If you belong to a special patient group, make sure you receive education/counselling about getting vaccinated from a health care provider prior to getting vaccinated.

Upon request, or if you have an allergy to mRNA vaccines (like Pfizer or Moderna), or you do not want to receive an mRNA vaccine you can get Janssen , Astra Zeneca or Novavax vaccine.

Due to limited supply and vaccine logistics, these vaccines are a special order and you will be required to travel to a central location to receive the vaccine.

  • You must request any of the above vaccines through the health unit. Please use the online form to request to be put on a list to receive one of the above listed vaccines.
  • The National Advisory Committee on Immunization recommends that a booster dose of an mRNA COVID-19 vaccine should be offered six months after completion of a primary series of Astra Zeneca, Janssen or Novavax. If you have an allergy to an mRNA vaccine, speak with your health care provider about appropriate next steps for a booster dose.

Eligible individuals aged 12+ who have had any COVID-19 vaccine not authorized by Health Canada are recommended to receive one additional dose of a Health Canada approved vaccine to complete their primary series. The vaccine dose to complete the primary series is recommended at least 28 days after the most recent dose of vaccine not approved by Health Canada. 

Proof of previous vaccination and/or self-attestation of previous vaccination may be required.

After the primary series is completed with one dose of a Health Canada approved vaccine, boosters are also recommended for everyone 12+:

  • three months after completion of the primary series for adults 18+
  • six months after completion of the primary series for youth 12 to 17.
Ready to get vaccinated?

People 12+ Who Are Immunocompromised (extended primary series)

For individuals who are moderately or severely immunocompromised, a three-dose primary series is recommended. A third dose is recommended because people who are moderately or severely immunocompromised:

  • get less immunity protection from two doses compared to those who are healthy, and
  • are at greater risk of getting seriously sick if they get COVID-19.

In addition to a three-dose extended primary series, a fourth dose (or booster) is also recommended for eligible immunocompromised individuals 12+, including those who are not receiving treatment at this time.  

NEW: Individuals 60+ who are immunocompromised and 18+ who are immunocompromised and self-identify as First Nation, Metis, and Inuit, including immunocompromised household members, are eligible to book a fifth booster dose appointment by calling the Provincial Vaccine Contact Centre at 1-833-943-3900. Booking an appointment through the online portal will be available on May 20th, 2022.

Immunocompromised individuals 12+ who are eligible for an extended three-dose primary series and a fourth (booster) dose include those who are:

  • receiving dialysis (hemodialysis or peritoneal dialysis)
  • receiving active treatment (e.g., chemotherapy, targeted therapies, immunotherapy) for solid tumour or hematologic malignancies
  • recipients of solid-organ transplant and taking immunosuppressive therapy
  • recipients of chimeric antigen receptor (CAR)-T-cell therapy or hematopoietic stem cell transplant (within 2 years of transplantation or taking immunosuppression therapy)
  • diagnosed with moderate to severe primary immunodeficiency (e.g., DiGeorge syndrome, Wiskott-Aldrich syndrome)
  • diagnosed with stage 3 or advanced untreated HIV infection and those with acquired immunodeficiency syndrome
  • receiving active treatment with the specific immunosuppressive therapies.

An extended three-dose primary series is also recommended for immunocompromised children five to 11 years of age.

Third dose

Eligible individuals who are severely or moderately immunocompromised can get a third dose of the COVID-19 vaccine eight weeks after their second dose as part of an extended primary series.

Fourth dose (Booster)

Adults 18+:

The recommended interval is three months (84 days) after completion of the three-dose primary series.

Youth 12 to 17:

The recommended interval is at least six months (168 days) after completion of the three-dose primary series.

Note: With informed consent, individuals 12 to 17 can get a third dose (to complete their primary series) and a fourth dose (booster) at three months (84 days).

NEW:  Fifth dose (Booster)

Adults 60+:

The recommended interval is five months (140 days) or a minimum interval of three months (84 days) from your last booster dose.

Adults 18+ who self-identify as First Nations, Metis, and Inuit, including immunocompromised household members:

The recommended interval is five months (140 days) or a minimum interval of three months (84 days) from your last booster dose.

After Infection

It is suggested that moderately to severely immunocompromised youth and adults 12+ who experience a COVID infection before or between doses of their primary series (three doses) receive their next dose four to eight weeks after symptom onset or a positive test.

Ready to get vaccinated?


VaxFacts - Scarborough Health Network has qualified doctors who understand you may have questions or concerns about the COVID-19 vaccines. They are ready to listen and talk with you in a one-to-one by appointment phone call. The call is a judgement-free conversation in a safe space to give you the facts that will help you make an informed decision. Visit their website for more information or to book your appointment.

For multilingual information and resources on COVID-19 vaccines, please visit:

  • Black Scientists’ Task Force on Vaccine Equity

Dr. Zainab Abdurrahman Answers Questions on Vaccines & Side Effects Facebook video

COVID-19 Community Resources

Dr. Onye Nnorom’s thoughts on the vaccine  – YouTube video

Page last modified May 9, 2022

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