This information applies only to Pfizer BioNTech Comirnaty™ COVID-19 Vaccine approved for those 5-11 years of age. For information about Pfizer BioNTech Comirnaty™ for those ≥12 years of age, go here.
Product Information
  • Individuals 5 to 11 years of age
  • 2 x 0.2 ml (10 mcg mRNA) doses given IM (deltoid
    • The authorized interval between the 1st and 2nd doses is 21 days.
    • The optimal interval is 8 weeks, as recommended by the Ministry of Health and NACI.
      • 8 weeks is recommended, but dose can be provided at a shorter interval (≥ 21 days) if chosen.
    • Based on NACI recommendation, the minimum interval is 19 days between doses (any doses provided at an earlier interval would be considered invalid and need to be repeated).
      • This interval is not a recommended interval and should only be used to determine dose validity.
    • If the interval is longer than recommended, there is no reason to restart the series. Provide the next dose as soon as possible.

  • For children who received the 12+ vaccine as a first dose and are still 11 when they present for their second dose, complete the series with the 5-11 vaccine formulation (10 mcg mRNA).

  • For children who received the 5-11 vaccine as a first dose and are 12 years old when they present for their second dose, complete the series with the 12+ vaccine formulation (30 mcg mRNA).

  • See "Why are 5-11 year olds getting a smaller dose?" and "How long should I wait between 1st and 2nd doses?" below for more information.
Adverse Effects
  • Only short to medium term data are available at this time. Surveillance will continue for long-term adverse effects.
  • Reported adverse effects were mild or moderate, resolved within 1-2 days, and included:  
    • More common
      • local reactions: pain at injection site, redness, and swelling (up to 74%)
      • fatigue (39%)
      • headache (28%)
      • muscle pain (12%)
    • Less common (<10%)
      • fever
      • chills
      • vomiting/diarrhea
      • muscle/joint pain
    • Adverse effects were more common following the 2nd dose. 
    • Rare Adverse Effects
      • No cases of myocarditis, pericarditis, anaphylaxis, Bell’s palsy, or appendicitis reported. However, these would not be expected given the size of the trial and will continue to be monitored.
  • See "What do we know about safety when it comes to the Pfizer COVID-19 vaccine?" below for further discussion.
Drug Interactions
  • There are no known drug interactions.

19 Nov 2021

  • <5 years or 12 years of age
    • This formulation of Pfizer-BioNTech is approved for use in persons 5-11 years of age only.
    • A different Pfizer-BioNTech Comirnaty™ formulation is approved for use in persons ≥12 years. See information here 

  • Serious adverse or allergic reaction to previous dose of COVID-19 vaccine unless determined safe by an allergist or other healthcare provider.

  • Reported hypersensitivity to one of the ingredients. See product monograph for ingredients. Note the formulation of this vaccine differs from the formulation for those 12 years and older. 
    • polyethylene glycol (PEG) and tromethamine are potentially allergenic ingredients 
    • See "What’s in Pfizer COVID-19 vaccine for kids 5-11 years?" below for more information.

  • Currently feeling unwell with symptoms that could be COVID-19.
    • to avoid confusion if symptoms arise/worsen as they could be adverse effects of the vaccine or because of the underlying infection
    • to prevent potential transmission to others who are at the vaccine clinic/site (clients should be following public health quarantine recommendations)

  • Some children were excluded from the trial so we have no data on these populations:
    • Immunocompromised/immunosuppressed because of condition or medications.  There is no specific recommendation for this particular population. Consider:
      • These individuals are at higher risk of contracting COVID-19 and higher risk of more severe complications.
      • In immunocompromised/immunosuppressed adults, vaccine response is lower (than the general population) and this can also be expected for children; individuals need to continue to take precautions against COVID-19 disease.
    • History of multisystem inflammatory syndrome in children (MIS-C)
      • NACI and the MoH recommend that for children with a previous history of MIS-C, vaccination should be postponed until clinical recovery has been achieved or until it has been ≥ 90 days since diagnosis, whichever is longer.

  • History of myocarditis or pericarditis
    • As a precautionary measure, and consistent with current recommendations for adolescents and adults, NACI and the MoH recommend the second dose should be deferred in children who experience myocarditis or pericarditis following the first dose of the Pfizer-BioNTech COVID-19 vaccine until more information is available.
    • Children who have a history of myocarditis unrelated to mRNA COVID-19 vaccination should consult their clinical team for individual considerations and recommendations. If they are no longer followed clinically for cardiac issues, they may receive the vaccine.

23 Nov 2021

The information that we have on vaccine efficacy currently comes from a large ongoing clinical trial. 

Here are a few important things to know about the clinical trial: 

  • Children from 4 countries were included: the US, Finland, Spain and Poland. 
  • Trial studied 10 mcg mRNA vaccine regimen of 2 doses given 21 days apart. 
  • 2268 children were initially enrolled in June-Sept 2021 and these children were followed for an average of 3.3 months after receiving the 2nd dose. 1518 children received vaccine, 750 received placebo. 
  • Another 2379 children were enrolled in Aug-Sept 2021 and were followed for about 2.4 weeks after receiving the 2nd dose. 1591 received vaccine, 778 received placebo.  This group was added as a “safety expansion” to address concerns about adverse effects in children. 
  • Vaccine efficacy was determined in two ways in the trial:   
    • Antibody response compared to 16-25 year olds. 
      • The neutralizing antibody numbers in kids 5-11 years old were comparable to neutralizing antibody numbers in the clinical trials done previously in 16-25 year olds. The antibodies were measured at 1 month after dose 2. Showing the same response indicates that the vaccine is effective.
    • Vaccine efficacy. 
      • There were 19 total cases of COVID-19 in the trial. 16 cases occurred in the placebo group, 3 cases in the vaccine group = 90.7% efficacy.
  • The clinical trial was done at a time when the Delta variant was circulating, and the trial results included a small amount of specific data on efficacy against Delta variant.  The vaccine showed good efficacy against the Delta variant, and a comparable response to wild type infection at 1 month post vaccination.   

There are a few things about effectiveness that this trial didn’t look at, but certainly we can expect more evidence and information to become available as the vaccine will continue to be studied and very closely monitored. 

  • The trial didn’t look at efficacy against asymptomatic COVID-19 infection. 
  • The trial didn’t look specifically at transmission, but it would be reasonable to assume that we can expect similar “real world” transmission results because the efficacy is similar to what we see with kids over the age of 12 and adults.
  • The trial wasn’t long enough to study how long protection will last and whether or not vaccine efficacy will wane over time, but the trial is ongoing and we can expect more data on this to come.
  • Pfizer.  BNT162b2 Comirnaty Vaccines and Related Biological Products Advisory Committee Briefing Document from VRBPAC Oct 26, 2021 Meeting.  Available from:
  • Walter EB, Talaat KR, Sabharwal C, et al; C4591007 Clinical Trial Group. Evaluation of the BNT162b2 Covid-19 Vaccine in Children 5 to 11 Years of Age. N Engl J Med. 2021 Nov 9. doi: 10.1056/NEJMoa2116298.

18 Nov 2021

  • The clinical trial reported on safety and side effects with the vaccine in 5 to 11 year olds. Most of the side effects were mild to moderate, meaning they were a bit uncomfortable, but completely manageable. The side effects that happened were not unexpected, and this information gives parents and caregivers some information about how to prepare their kids for getting the vaccine.

  • Local side effects, or the “arm reactions” included redness, swelling, and pain. About 70% of kids reported pain.   
  • There were also some systemic reactions, or the “full body” reactions reported including fatigue, headache, and muscle pain. Fever, chills, and muscle pain occurred less frequently in 5 to 11 year olds than they did in older kids and adults.

  • More kids reported side effects after the 2nd dose than the 1st dose. Most side effects went away within 1-2 days. 

  • Local or systemic side effects are entirely normal and expected part of getting a vaccine.  Side effects might slow children down for a day or two. Allow them to rest, give them some acetaminophen or ibuprofen if they need it. Some kids may not notice any of these side effects, which is also entirely expected.   

  • There were few reports of lymph node swelling (less than 1% of kids that received vaccine) and skin rash (less than 0.05% of kids that received vaccine).

  • There were no serious side effects like myocarditis and anaphylaxis reported that were associated with the vaccine, and there were no reports of death.   

  • The trial followed the initial group of kids for an average of about 3 months past the 2nd dose and the safety expansion group was followed for around 2.5 weeks following the 2nd dose.  Most side effects with vaccines occur very close to when the vaccine is given, or within 6-8 weeks of receiving a vaccine dose. 

  • An important limitation to note is that because of the size of the trial, rare side effects are unlikely to happen because these side effects occur infrequently. It isn’t logistically possible to include hundreds of thousands of kids in the clinical trials to pick up on these very rare side effects, but the vaccine will continue to be monitored very closely to watch for these possible but rare side effects.
  • Pfizer.  BNT162b2 Comirnaty Vaccines and Related Biological Products Advisory Committee Briefing Document from VRBPAC Oct 26, 2021 Meeting.  Available from:
  • Walter EB, Talaat KR, Sabharwal C, et al; C4591007 Clinical Trial Group. Evaluation of the BNT162b2 Covid-19 Vaccine in Children 5 to 11 Years of Age. N Engl J Med. 2021 Nov 9. doi: 10.1056/NEJMoa2116298.
  • Centers for Disease Control and Prevention.  Possible Side Effects After Getting a COVID-19 Vaccine.  Updated 3 Nov 2021.  Available from:  

18 Nov 2021

  • COVID-19 vaccines have gone through the usual process for vaccine approval in Canada.
  • When researchers do a clinical trial, they use a calculation to help determine how many people need to be included in the trial to make sure the results are valid. This number is called sample size. The clinical trials for ages 5 to 11 used this calculation in figuring out how many kids to include. In fact, the trials added more kids at the request of the regulatory body in the US (the FDA) to get additional information about safety and adverse effects.   

  • Clinical trials include enough people to be able to detect common and uncommon side effects. It can be difficult to detect very uncommon and rare side effects, but it is logistically impossible to include enough people in a trial to pick up on these. This is one of the reasons why ongoing monitoring is required even after a vaccine is approved for use. Clinical trials provide enough information about safety and efficacy for approval, but ongoing research and surveillance is essential to the process and is mandatory. As the vaccine is rolled out to kids aged 5 to 11, researchers, regulatory bodies, and healthcare professionals will be monitoring the vaccine.  

  • Having a vaccine available has happened faster than usual because of the need for a vaccine, and because of the collective global effort by science and medical communities and the regulatory bodies that approve vaccines. The time that was saved in approving the vaccine was not at the expense of safety; there were no shortcuts taken when approving the vaccines in terms of safety or efficacy. Time was saved because the approval process was made much more efficient, and the steps that typically take a lot of time and resources were streamlined - things like finding research funding, recruiting study participants, and waiting for regulatory review.  It would be like applying for a passport.  Anyone who has gone through the process knows that there are many steps and that it can take months to get a passport in Canada.  If you could do all the steps in a very efficient way, you could likely get a passport in a day! 

  • Another consideration is that the COVID-19 vaccines are also based on the many years of vaccine research that we have available. The SARS outbreak that occurred in 2003 was because of a coronavirus and provided researchers with a lot of data to help understand SARS-CoV-2. 

  • While some people have expressed concern that the mRNA vaccines are too new. The use of mRNA isn’t new: scientists have been researching how mRNA can be used in medicine for many years. In fact, research into using mRNA specifically for vaccines started as early as the 1990s and the first clinical trial of an mRNA vaccine started in 2006. 
  • Although we don’t have a lot of real-world experience with COVID-19 vaccines in kids yet, there is some reassurance to be found in the number of vaccines that have been given to older kids and adults.  As of mid-November 2021, 59.2 million doses of COVID-19 vaccines have been given in Canada. 7.31 billion doses of COVID-19 vaccines have been administered globally.


18 Nov 2021

  • Vaccines aren’t dosed based on weight, as immune response is not weight-dependent. This is different from most medications that we use in kids, which are dosed according to weight because weight can impact how our bodies process medicine, but vaccines do not rely on these same processes.  The other important thing to note is that younger kids tend to have an immune system that is more responsive than older kids and adults – this is nature’s way of protecting kids since their immune system isn’t as experienced and is still learning.

  • The dose for the Pfizer vaccine was determined based on a clinical trial.  The researchers looked at several doses (10 mcg, 20 mcg, and 30 mcg) in kids from ages 5-11.  Each of the three doses that were tested showed similar efficacy, meaning they all worked well.  However, the kids that received higher doses had more side effects.  The researchers decided on the 10 mcg dose because it produced an effective response but minimized side effects.  
  • Something that hasn’t been studied is what would happen if you gave the lower 10 mcg dose to a 12 year old or older kid. We do know that the levels of antibodies with 12-15 year olds that get 30 mcg are quite high so a 10 mcg dose is likely to work, but this has not been studied yet.  
  • Based on the data that we have, 11 year old = 10 mcg dose, 12 year old = 30 mcg dose. These doses have been shown to be safe and effective, and there is no reason to wait or delay vaccination to get a higher dose.   
  • Walter EB, Talaat KR, Sabharwal C, et al; C4591007 Clinical Trial Group. Evaluation of the BNT162b2 Covid-19 vaccine in children 5 to 11 years of age. N Engl J Med. 2021 Nov 9. doi: 10.1056/NEJMoa2116298. 

18 Nov 2021

  • The Pfizer vaccine for kids 5-11 years old is a different formulation from the adult formulation.  The manufacturers added a different ingredient (tromethamine) to help stabilize the vaccine so that it could be more easily stored.  
  • List of ingredients: 
    • 10 mcg mRNA to make viral spike (S) glycoprotein of SARS-CoV-2
    • Lipids - (0.14 mg (4- hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 0.02 mg 2[(polyethylene glycol)-2000]- N,N-ditetradecylacetamide, 0.03 mg 1,2-distearoyl-sn-glycero-3-phosphocholine, and 0.06 mg cholesterol)
    • Sodium Chloride
    • Sucrose
    • Tromethamine
    • Tromethamine Hydrochloride 
    • Water for Injection

  • mRNA is the active ingredient in Pfizer-BioNTech Comirnaty™ and Moderna Spikevax™ COVID-19 vaccines. mRNA is used to instruct our bodies to make a spike protein so that our immune system can respond to it and learn how to protect us from getting infected if we are exposed to COVID-19. 

  • Lipids are used to contain the mRNA. mRNA is fragile, so it is coated with lipids to protect it and help it get into our cells. 

  • Sucrose is sugar and is added to protect and stabilize the vaccine while it is frozen. 

  • Tromethamine helps to keep the vaccine stable while it is being stored. 
    • People have been asking about tromethamine (AKA: TRIS, tris(hydroxymethyl)aminomethane, THAM, trometamol). 
    • Tromethamine is a buffer used to adjust the pH of the vaccine and helps to keep the vaccine stable. It is commonly used in other products like medicines, creams, lotions, and makeup. 
    • Tromethamine is available in the US (not Canada) as a treatment for metabolic acidosis but is NOT a treatment for myocarditis and has not been added to the vaccine as a treatment. 
    • Tromethamine is in the Moderna Spikevax™ COVID-19 vaccine for adults. 

  • The vaccine also contains and is diluted with sodium chloride & water for injection, which is salt water. 

19 Nov 2021

  • The intervalstudiedin the clinical trials for kids 5-11 years old was 2 doses given 21 days apart.  This is the amount of time that there needs to be between the two doses in order to get the expected vaccine response.  

  • The interval recommended in Saskatchewan is 8 weeks.
  • The National Advisory Committee on Immunization (NACI) is the vaccine expert committee in Canada and has recommended at least 8 weeks between the 1st and 2nd doses for kids 5-11. This is based on a few important things: 
    • Shorter intervals between doses of COVID-19 vaccines result in lower levels of the antibodies produced in adults, and this may decrease effectiveness.
    • The evidence we have from adults shows that a longer interval (i.e.: at least 8 weeks) improves the immune response and might last longer.
    • New data from adolescents and adults show that a longer interval might reduce the risk of myocarditis/pericarditis.

  • These different recommendations for interval may seem confusing and worrisome, but it makes sense when you look at all of the factors that need to be considered in order to give people the best protection during a rapidly changing pandemic.
    • When researchers were first developing the vaccines, there was a need to get many people vaccinated quickly. It makes sense that we would want to know the minimum amount of time between the doses. 
    • When COVID-19 vaccines were introduced in adults, extended intervals (up to 4 months) were used at first because of the limited supply available.  Based on what we know about other vaccines that have longer intervals (like Hepatitis A, which is 6 months between dose 1 and 2), this made sense. 
    • Since then, a range of intervals has been used around the world in order to balance supply and the need for protection. 

  • A longer interval between doses in adults showed an improved immune response which might last longer, but a second dose provides more protection than just one dose. When there is evidence of rapid spread within our communities, we want to get people protected as quickly as possible. It is necessary to weigh all of these factors to come up with an ‘optimal’ interval. It is a balance of efficacy and safety. It is reassuring that experts use clinical trial information and real-world evidence in order to determine this optimal interval.

23 Nov 2021


5-11 Years ≥12 Years
Colour on vial label (border), carton, dust cap Orange Purple
(Note: vials in current inventory may not yet have purple border on label)
Dose 0.2 mL (10 mcg) 0.3 mL (30 mcg mRNA)
# Doses per Vial 10 6
Determination of Expiry Date Date on label/carton is date of manufacture
EXPIRY date is 6 months from date of manufacture
when stored at -90°C to -60°C

Do not use product beyond 6 months from date on label/carton
Date on label/carton is expiry date when stored at -90°C to -60°C with caveat that the expiry date of those labelled between Aug 2021 and Feb 2022 have been extended by 3 months
See details here
Volume of 0.9% Sodium Chloride USP for Reconstitution 1.3 mL 1.8 mL
-90°C to -60°C (Ultra Freezer) 6 months from date printed on label
(date printed is date of manufacture)
Until expiry date printed on label with caveat that the expiry date of those labelled between Aug 2021 and Feb 2022 have been extended by 3 months
See details here
-25°C to -15°C Do not store at this temperature

Up to 2 weeks

Thawing Thaw undiluted product in fridge
(takes up to 4 hours)
Thaw undiluted product at room temperature
(takes ~30 minutes)

Do not refreeze thawed vials
Thaw undiluted product in fridge
(takes up to 3 hours)
Thaw undiluted product at room temperature
(takes ~30 minutes)

Do not refreeze thawed vials
(2°C to 8°C)
Unreconstituted Up to 10 weeks Up to 1 month
Reconstituted Up to 12 hoursa Up to 6 hours
Room Temperature
(Up to 25°C)
Unreconstituted Up to 12 hours Up to 2 hours (including thaw time)
Reconstituted Up to 12 hoursa Up to 6 hours
Formulation Active Ingredient nucleoside modified messenger RNA (modRNA) encoding the viral spike (S) glycoprotein of SARS-CoV-2
Inactive Ingredients - ALC-0315 = ((4-hydroxybutyl) azanediyl)bis(hexane-6,1-diyl)bis(2- hexyldecanoate)
- ALC-0159 = 2-[(polyethylene glycol)-2000]- N,N-ditetradecylacetamide*
- 1,2-distearoyl-sn-glycero-3-phosphocholine
- Cholesterol
- Sodium chloride
- Sucrose
- Tromethamine*
- Tromethamine hydrochloride*
- Water for injection
- ALC-0315 = ((4-hydroxybutyl) azanediyl)bis(hexane-6,1-diyl)bis(2- hexyldecanoate)
- ALC-0159 = 2-[(polyethylene glycol)-2000]- N,N-ditetradecylacetamide*
- 1,2-distearoyl-sn-glycero-3-phosphocholine
- Cholesterol
- Dibasic sodium phosphate dihydrate
- Monobasic potassium phosphate
- Potassium chloride
- Sodium chloride
- Sucrose
- Water for injection
* Polyethylene glycol (PEG) and Tromethamine are potentially allergenic
a. Vial labels and cartons may state that a vial should be discarded 6 hours after dilution, however, additional testing has been completed to support 12 hours of stability after dilution.


23 Nov 2021