COVID-19 vaccine guide for youth and adults (12 years and over): Recommendations for use

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Information on adverse events following immunization

Immunization may trigger common side effects such as a sore arm, fatigue, headache, sore muscles and joints, and fever. These side effects are often mild and don't last more than a few days.

In addition to discussions about these common side effects, health care providers should offer information on the specific adverse events that may occur following receipt of COVID-19 vaccines.

mRNA vaccines and the risk of myocarditis/pericarditis

Myocarditis is an inflammation of the heart muscle and pericarditis is an inflammation of the tissue surrounding the heart.

Myocarditis and pericarditis have been reported after vaccination with mRNA vaccine. Most cases are mild and symptoms resolve quickly after seeking medical care.

Although rare, the risks of myocarditis/pericarditis from mRNA vaccines are higher:

NACI has indicated that, to minimize the risk of myocarditis/pericarditis, the Pfizer-BioNTech Comirnaty product is the preferred vaccine for the primary series in those 12 to 29 years of age. It may also be the preferred product for the booster dose in those 18 to 29 years of age. However, Moderna Spikevax (100 mcg) may be considered for those 12 to 29 years of age who are moderately or severely immunocompromised based on clinical judgment.

Table 1 provides a summary of recommendations of products and doses by age.

Vaccinated people should be advised to seek medical attention immediately if they develop any of the following:

mRNA vaccines and Bell's palsy

Bell's palsy is a weakness or inability to move the muscles of the face and has been very rarely reported after mRNA vaccines.

Vaccinated people should be informed to seek medical attention if they experience facial weakness or drooping or other symptoms involving the face.

Viral vector vaccines and the risk of vaccine-induced immune thrombotic thrombocytopenia (VITT)

VITT (also called thrombosis with thrombocytopenia syndrome, or TTS) is a serious condition involving thrombosis (blood clotting) and thrombocytopenia (low platelets, a part of the blood used for clotting). Blood clots can develop in the brain, abdomen, legs and other parts of the body.

VITT has been reported to occur in about 1 in 50,000 people who receive a first dose of the AstraZeneca Vaxzevria/COVISHIELD vaccine and about 1 in 600,000 to 750,000 people who receive a second dose of the AstraZeneca Vaxzevria/COVISHIELD vaccine. The risk is about 1/300,000 after the Janssen vaccine. About 1 in 5 people who develop VITT after the AstraZeneca Vaxzevria/COVISHIELD vaccine die. Deaths have been reported after the Janssen vaccine as well.

Because of the risk of VITT with viral vector vaccines, mRNA vaccines are preferred.

If someone receives a viral vector vaccine, they should be advised to seek medical attention immediately if they develop any of the following:

Symptoms usually develop within 4 to 28 days after vaccination, but can develop as late as 42 days after vaccination.

Viral vector vaccines and Guillain-Barré Syndrome (GBS)

Guillain-Barré syndrome (GBS) has very rarely been associated with viral vector vaccines. GBS is a potentially serious neurologic disorder that results in numbness and weakness in the arms, legs or other muscles, causing paralysis in severe cases.

Most people fully recover from GBS but some have remaining symptoms and fatal cases can occur.

Patients receiving a viral vector vaccine should be advised of the risk of GBS and to seek health care if symptoms develop.

Viral vector vaccines and capillary leak syndrome

Capillary leak syndrome has very rarely been associated with viral vector vaccines. Capillary leak syndrome is serious and sometimes fatal condition that causes fluid to leak from small blood vessels, causing rapid swelling of the arms and legs, sudden weight gain and low blood pressures resulting in feeling faint.

Those who have previously had capillary leak syndrome appear to be at increased risk following vaccination with a viral vector vaccine. They should not receive a viral vector vaccine.

Patients receiving a viral vector vaccine should be advised of the risk of capillary leak syndrome and to immediately seek health care if symptoms develop.

Viral vector vaccines and immune thrombocytopenia

Immune thrombocytopenia results in low platelets that can cause easy or excess bruising or bleeding. It has been very rarely associated with viral vector vaccines and can occur within 4 weeks of vaccination. Cases can be fatal.

Symptoms of immune thrombocytopenia include unexplained bleeding or bruising or small purplish pinpoint spots under the skin.

Some of the cases of immune thrombocytopenia after vaccination have occurred in people with a past history of low platelets. Along with NACI's preference for mRNA vaccines, consider if the client has a past history of thrombocytopenia if considering a viral vector vaccine.

Viral vector vaccines and venous thromboembolism

Viral vector vaccines have very rarely been associated with venous thromboembolism.

Venous thromboembolism can cause blood clots in the deep veins such as in the legs, arms or groin. The clots can embolize to the lungs, causing serious illness. Symptoms include leg pain, leg swelling, persistent abdominal pain, shortness of breath and chest pain.

Along with NACI's preference for mRNA vaccines, consider the patient's underlying risk of venous thromboembolism if considering a viral vector vaccine.

Patients receiving a viral vector vaccine should be advised of the risk of venous thromboembolism and to immediately seek health care if symptoms develop.

Anaphylaxis after all COVID-19 vaccines

Anaphylaxis is a very rare but potentially serious allergic reaction that can occur after vaccination, usually within the first few minutes to hours after vaccination.

Vaccine recipients should be advised to seek medical attention immediately if they develop any of the following:

Refer to "Contraindications, precautions and possible allergic reactions" for more information on how to manage people potentially at increased risk for these adverse events following immunization.

Interchangeability between vaccines

mRNA vaccine interchangeability:

Table 1 provides a summary of recommendations of products and doses by age.

Second dose and booster dose after viral vector vaccines:

A vaccine series started with AstraZeneca Vaxzevria/COVISHIELD may be completed either with the AstraZeneca Vaxzevria vaccine or an mRNA vaccine (Pfizer-BioNTech Comirnaty or Moderna Spikevax). However, an mRNA vaccine is preferred because of:

If receiving the AstraZeneca Vaxzevria vaccine, clients should be counselled about the risk of VITT. This is estimated to occur in about 1 in 600,000 to 750,000 people vaccinated with a second dose of AstraZeneca Vaxzevria. This is lower than the risk of VITT after the first dose of AstraZeneca Vaxzevria (about 1 in 50,000 people).

mRNA vaccines should be used as the booster dose regardless of the product(s) used for the initial series (AstraZeneca Vaxzevria/COVISHIELD or Janssen COVID-19 vaccine).

Table 1 provides a summary of recommendations of products and doses by age.

Intervals between first and second doses

NACI recommends that for those who have not completed their primary series, the optimal interval between the first and second dose is 8 weeks. This interval provides enhanced protection from a longer interval while at the same time minimizing the risk of infection due to having protection from only 1 dose. It also minimizes the risk of myocarditis/pericarditis (which appears to be lower with longer intervals between doses).

Refer to the Additional dose and Booster dose sections for information on the interval between the initial series and additional or booster doses.

Youth 12 to 17 years of age

The Pfizer-BioNTech Comirnaty vaccine is preferred for the initial series in youth 12 to 17 years old to minimize the risk of myocarditis/pericarditis. Moderna Spikevax (100 mcg) may be considered in those who are moderately to severely immunocompromised based on clinical judgment. Booster doses are not authorized or recommended for those under 18 years of age.

The dose of Pfizer-BioNTech Comirnaty in youth 12 to 17 years of age is 30 micrograms (the adult/adolescent formulation). Table 1 provides a summary of recommendations of products and doses by age.

Children who are turning 12 years of age between their first and second dose should receive the:

If a youth 12 to 17 years of age inadvertently receives a 10-microgram dose of the Pfizer-BioNTech Comirnaty vaccine instead of the 30-microgram dose, the dose should be considered valid.

Additional doses

An additional dose is recommended for people 12 years of age and over who are moderately or severely immunocompromised. It should be given at least 28 days after the initial series. This dose would be considered a third dose in a primary series. (Consult the NACI statement for a list of specific conditions.)

For those 12 to 29 years of age, Pfizer-BioNTech Comirnaty is preferred for the primary series in this age group (to minimize the risk of myocarditis/pericarditis). However, NACI notes that moderately and severely immunocompromised individuals may benefit from the slightly higher antibody levels generated and slightly higher vaccine effectiveness provided by the Moderna 100 mcg vaccine compared to the Pfizer-BioNTech 30mcg vaccine. Moderna Spikevax (100 mcg) may be considered as the additional dose in those who are moderately or severely immunocompromised based on clinical judgment.

Table 1 provides a summary of recommendations of products and doses by age.

Booster doses

NACI recommends that a booster dose should be offered for:

NACI is also recommending that a booster dose may be offered for those 18 to 49 years of age.

Booster doses should be given at least 6 months after the last dose in the primary series.

Pfizer-BioNTech Comirnaty may be the preferred product for the booster dose in those 18 to 29 years of age due to a lower risk of myocarditis/pericarditis. However, NACI notes that moderately and severely immunocompromised individuals may benefit from the slightly higher antibody levels generated and slightly higher vaccine effectiveness provided by the Moderna 100 mcg vaccine compared to the Pfizer-BioNTech 30mcg vaccine. Moderna Spikevax may be considered for those 18 to 29 years of age who are moderately or severely immunocompromised based on clinical judgment.

Either Pfizer-BioNTech Comirnaty and Moderna Spikevax vaccines can be used as the booster dose in those 30 years of age and over.

If Moderna Spikevax is being used as a booster dose, 100 mcg may be preferred for people who:

Please note that the authorized booster dosage for Moderna Spikevax is 50 mcg. NACI recommends this dose for all other groups receiving Moderna Spikevax as the booster dose.

All doses should be considered valid and not repeated if:

Table 1 provides a summary of recommendations of products and doses by age.

Timing COVID-19 vaccination with other vaccinations

For those 12 years of age and over, NACI recommends giving a COVID-19 vaccine at the same time as any other vaccine or at any time before or after any other vaccine.

If more than 1 vaccine is administered at a single visit, they should be administered at different injection sites using separate injection equipment.

Timing COVID-19 vaccination with monoclonal antibodies or convalescent plasma

NACI recommends that COVID-19 vaccines not be given at the same time as anti-SARS-CoV-2 monoclonal antibodies or COVID-19 convalescent plasma. The optimal interval to wait between these products and COVID-19 vaccination is not known. Some guidance is available from the Centers for Disease Control and Prevention (CDC). Expert clinical opinion should be sought on a case-by-case basis.

Timing COVID-19 vaccination with tuberculosis skin tests (TST) or interferon gamma-release assays (IGRA) to test for tuberculosis

Tuberculosis skin testing or an IGRA test should be administered and read before COVID-19 vaccination or delayed at least 4 weeks after COVID-19 vaccination. If an opportunity to perform the TST or IGRA test may be missed, testing should not be delayed. However, it may be prudent to re-test (at least 4 weeks post-COVID-19 vaccination) people with negative results who are suspected of having tuberculosis. Re-testing will help to avoid missing cases due to potentially false-negative results.

Vaccination with COVID-19 vaccines may take place at any time after all steps of tuberculin skin testing have been completed.

Vaccinating people with previous SARS-CoV-2 infection

It is very important for people with previous SARS-CoV-2 infection to be vaccinated to prevent becoming infected again. NACI recommends that a complete series with a COVID-19 vaccine may be offered to individuals (in the authorized age group without contraindications to the vaccine) who have previously had PCR-confirmed SARS-CoV-2 infection. The number of doses will be updated based on evolving evidence.

Table 1 provides a summary of recommendations of products and doses by age.

People with SARS-CoV-2 infection can be vaccinated once they are no longer infectious and no longer have acute symptoms of COVID-19. The optimal timing of vaccination after infection is not certain.

Vaccination during pregnancy and breastfeeding

People who are pregnant and breastfeeding should be vaccinated with COVID-19 vaccines (unless otherwise contraindicated). As for all individuals, mRNA vaccines are the preferred option because of their higher efficacy and because they are not known to carry a risk of VITT. There is also more safety data associated with mRNA vaccines in pregnancy than with viral vector vaccines.

Table 1 provides summary of recommendations of products and doses by age.

Vaccinating immunocompromised people and people with autoimmune disease

People who are immunocompromised and people with autoimmune diseases should be vaccinated with COVID-19 vaccines (unless otherwise contraindicated). As for all individuals, mRNA vaccines are the preferred option because of their higher efficacy and because they are not known to carry a risk of VITT and other serious adverse events.

A third dose is recommended for people who are moderately or severely immunocompromised. It should be given at least 28 days after the primary series. (Consult the NACI statement for a list of specific conditions.) A booster dose is also recommended at least 6 months after the third dose.

To minimize the risk of myocarditis/pericarditis, NACI has indicated that Pfizer-BioNTech Comirnaty is the preferred vaccine for the primary series in those 12 to 29 years of age. It may also be the preferred product for the booster dose in those 18 to 29 years of age. However, NACI notes that moderately and severely immunocompromised individuals may benefit from the slightly higher antibody levels generated and slightly higher vaccine effectiveness provided by the Moderna 100 mcg vaccine compared to the Pfizer-BioNTech 30mcg vaccine. Moderna Spikevax may be considered for those who are moderately or severely immunocompromised based on clinical judgment.

Table 1 provides a summary of recommendations of products and doses by age.

Ideally, the COVID-19 vaccine series should be completed 2 weeks before starting immunosuppressive therapy or when the patient is expected to have the most robust immune response in their therapy course. However, the COVID-19 vaccine can be given earlier in order to provide protection as soon as possible.

The immune response may be lower in those who are immunocompromised. As with everyone, these individuals should continue to follow public health recommendations on preventing infection with SARS-CoV-2 (such as wearing a mask, physical distancing and hand hygiene) even if they have been vaccinated. Vaccination of their close contacts will also help protect the person who is immunocompromised.

Managing people with a bleeding disorder or taking medication that affect blood clotting

When vaccinating someone with a bleeding disorder or someone who is taking medication that affects blood clotting, the Canadian Immunization Guide advises to:

Managing people prone to fainting

The Canadian Immunization Guide states that you can reduce the chances of someone fainting with the following measures:

Assess clients to determine if they have a history of fainting during medical procedures or vaccinations or if they look anxious, pale or sweaty. You may want to have these clients lay down on a mat in the first aid area or in a reclining chair (if available) to prevent fainting and injury during vaccination.

There are a number of ways to make vaccine injections more comfortable for adults. For additional guidance and resources on vaccination pain management for adults, please refer to Vaccination pain management for adults: Guidance for health care providers.

Managing people vaccinated with non-Health Canada-authorized vaccines

People planning to stay in Canada for longer periods of time (for example, to live, work or study) who have received 1 or 2 doses of a non-Health Canada-authorized vaccine should be offered 1 additional dose of an mRNA vaccine soon after they arrive.

Refer to COVID-19: Recommendations for those vaccinated with vaccines not authorized by Health Canada for those staying in Canada to live, work or study.

Table 1. Summary of NACI recommendations based on age.
Age Product and dose for primary series Booster recommendations Products and dose for booster

70 years and over

Moderna Spikevax 100 mcg or

Pfizer-BioNTech Comirnaty 30 mcg

Should receive a booster

Moderna Spikevax 100 mcgTable 1 Footnote a or Pfizer-BioNTech Comirnaty 30 mcg

50 to 69 years

Moderna Spikevax 100 mcg or

Pfizer-BioNTech Comirnaty 30 mcg

Should receive a booster

Moderna Spikevax 50 mcgTable 1 Footnote a or Pfizer-BioNTech Comirnaty 30 mcg

30 to 49 years

Moderna Spikevax 100 mcg or

Pfizer-BioNTech Comirnaty 30 mcg

MayTable 1 Footnote b receive a booster

Moderna Spikevax 50 mcgTable 1 Footnote a or Pfizer-BioNTech Comirnaty 30 mcg

18 to 29 years

Pfizer-BioNTech Comirnaty 30 mcg is preferredTable 1 Footnote c

MayTable 1 Footnote b receive a booster

Pfizer-BioNTech Comirnaty 30 mcg may be preferredTable 1 Footnote a Table 1 Footnote c

12 to 17 years

Pfizer-BioNTech 30 mcg is preferredTable 1 Footnote c

Booster not recommended at this time

Not applicable

5 to 11 years

Pfizer-BioNTech Comirnaty 10 mcg

Booster not recommended at this time

Not applicable

Table 1 Footnote a

NACI notes that compared to Pfizer-BioNTech Comirnaty (30 mcg), Moderna Spikevax (100 mcg) induces somewhat higher antibody levels, and the protection against infection and severe disease may be more durable. If Moderna Spikevax is being used as a booster dose, 100 mcg may be preferred for people who:

  • are moderately to severely immunocompromised
  • live in long-term care homes or other congregate living settings that provide care for seniors
  • are 70 years and over

Please note that the authorized booster dosage for Moderna Spikevax is 50 mcg.

Table 1 Return to footnote a referrer

Table 1 Footnote b

The following groups should receive a booster:

  • recipients of a viral vector vaccine series completed with only viral vector vaccines (AstraZeneca Vaxzevria/COVISHIELD or Janssen COVID-19 vaccine)
  • adults in or from First Nations, Inuit and Métis communities
  • adults who are frontline health care workers (having direct close physical contact with patients)

Table 1 Return to footnote b referrer

Table 1 Footnote c

NACI notes that moderately and severely immunocompromised individuals may benefit from the slightly higher antibody levels generated and slightly higher vaccine effectiveness provided by the Moderna 100 mcg vaccine compared to the Pfizer-BioNTech 30mcg vaccine. Moderna Spikevax may be considered for those who are moderately or severely immunocompromised based on clinical judgment.

Table 1 Return to footnote c referrer

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