Question Period Note: NACI RECOMMENDATIONS ON THE USE OF COVID-19 VACCINES

NACI may make recommendations that are broader or narrower than the conditions of use approved by Health Canada. As regulator, Health Canada rigorously evaluates safety and efficacy data from clinical trials before authorizing vaccines, but does not dictate practice of medicine or make recommendations on how the vaccines should be used for public health impact.

Key Messages
• Canada’s National Advisory Committee on Immunization (NACI) updates its recommendations on COVID-19 vaccines based on the latest scientific evidence and their expert opinions.
• COVID-19 vaccines, authorized for use in Canada, are saving lives and are essential to ending the pandemic.
• In addition to high vaccine coverage, public health measures continue to be essential to reduce and control transmission of the virus, especially variants.
If pressed on the use of the Pfizer-BioNTech vaccine in children 5-11 years of age
• NACI recommends that a complete series of the Pfizer-BioNTech COVID-19 vaccine may be offered to children 5-11 years of age who do not have contraindications to the vaccine, with a dosing interval of at least 8 weeks between the first and second dose.
• NACI recommends an interval of at least 8 weeks between doses due to emerging evidence in adults that suggests longer intervals between the first and second dose of a primary series results in a stronger immune response, higher vaccine effectiveness that is expected to last longer, and for mRNA vaccines, may be associated with a lower risk of myocarditis and/or pericarditis in adolescents and young adults.
• It is essential that children and their caregivers are supported and respected during the decision-making process so they are able to make an informed decision about COVID-19 vaccination.
If pressed on myocarditis and pericarditis in adolescents 12 to 29 years of age
• Rare cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the heart lining) following vaccination with COVID-19 mRNA vaccines have been reported in Canada and internationally.
• Most cases have occurred in males 12 to 29 years of age and after the second dose of an mRNA vaccine. Most cases have been mild and resolved quickly.
• NACI now recommends the Pfizer-BioNTech Comirnaty mRNA vaccine (30 mcg) as the preferred use in adolescents and young adults 12 to 29 years of age to further reduce the already rare risk of myocarditis/pericarditis following mRNA vaccination.
• Some provinces and territories have been using only the Pfizer-BioNTech Comirnaty vaccine for adolescents because there is more experience to date with this vaccine in adolescents.
If pressed on guidance on booster doses
• NACI recommends that a booster dose of an authorized mRNA COVID-19 vaccine may be offered to adults 18 to 49 years of age at least 6 months after completion of a primary COVID-19 vaccine series.
• Some groups of people are at higher risk of severe illness and of waning protection offered by the vaccine. NACI therefore also strongly recommends a booster dose of an mRNA COVID-19 vaccine should be offered at least 6 months after the completion of a primary series to adults 50 years of age and older; long-term care residents and seniors living in other congregate settings; people who received two doses of the AstraZeneca Vaxzevria/COVISHIELD vaccine or one dose of the Janssen vaccine; adults in or from First Nations, Inuit or Métis communities; and all frontline healthcare workers who have direct in-person contact with patients.
• Booster vaccine programs in Indigenous communities should be determined by Indigenous leaders and communities with health care and public health partners.
• People who are pregnant and breastfeeding and adults who are moderately to severely immunocompromised who have received a three-dose primary series are included in those who may receive a booster dose.

To date, NACI has published recommendations on the use of the Pfizer-BioNTech Comirnaty, Moderna Spikevax, AstraZeneca Vaxzevria, and Janssen COVID-19 vaccines, as well as guidance on subjects such as extended dose intervals, the interchangeability of vaccines, co-administration of COVID-19 vaccine with other vaccines, additional doses for immunocompromised individuals and the use of booster doses.
NACI continues to closely monitor the evolving evidence on COVID-19 and COVID-19 vaccines and updates recommendations as needed.
Pfizer-BioNTech vaccine in children 5-11 years of age
NACI recommends that a complete series of the Pfizer-BioNTech COVID-19 vaccine (10 mcg) may be offered to children 5-11 years of age who do not have contraindications to the vaccine, with a dosing interval of at least 8 weeks between the first and second dose. The pediatric formulation of the Pfizer-BioNTech vaccine is 10 mcg compared to the 30 mcg formulation authorized for adolescents and adults over 12 years of age.

When authorizing a vaccine, Health Canada reviews clinical trial data submitted by the manufacturer. When developing their recommendations, NACI reviews clinical trial data and data from real-world use of the vaccine. NACI recommends an interval of at least 8 weeks due to emerging evidence in adults that suggests that compared to shorter intervals, longer intervals between the first and second dose of a primary series results in a stronger immune response, higher vaccine effectiveness that is expected to last longer, and may be associated with a lower risk of myocarditis and/or pericarditis in adolescents and young adults.

As a precaution, children who experience myocarditis and/or pericarditis after a first dose of the vaccine should wait to get a second dose until more information is available. Children who have a history of myocarditis unrelated to COVID-19 vaccination should consult their clinical care team for individual considerations and recommendations. If they are no longer under active care for myocarditis, they may receive the vaccine. Caregivers should be advised to seek medical attention for children if they develop symptoms including chest pain, shortness of breath, or palpitations following receipt of a COVID-19 vaccine.

At this time, NACI recommends that children receive the Pfizer-BioNTech COVID-19 vaccine (10 mcg) at least 14 days before or after another vaccine. This is a precaution to help to determine if a side effect that may arise is due to the COVID-19 vaccine or another vaccine. There may be circumstances when a dose of a COVID-19 vaccine and another vaccine need to be given at the same time – a healthcare provider can help with this decision.

Children with previous COVID-19 infection may be offered two doses of the vaccine once symptoms of acute illness have resolved and the child is no longer considered infectious, based on current criteria. Children with a history of MIS-C may be vaccinated once they have recovered or once it has been more than 90 days since diagnosis, whichever is longer.

Children who receive the pediatric formulation of the Pfizer-BioNTech COVID-19 vaccine (10 mcg) for their first dose who turn 12 by the time of their second dose may receive the adolescent/adult formulation of the Pfizer-BioNTech COVID-19 vaccine (30 mcg) to complete their primary series. If a child who has turned 12 by the time of their second dose receives the pediatric formulation (10 mcg), their series should still be considered valid and complete.

Health Canada, the Public Health Agency of Canada and NACI will continue to monitor the safety and effectiveness of the Pfizer-BioNTech vaccine (10 mcg) in children 5-11 years of age.

The use of mRNA vaccines in adolescents and young adults 12 to 29 years of age
Rare cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the heart lining) following vaccination with COVID-19 mRNA vaccines have been reported in Canada and internationally. Most cases have occurred in males 12 to 29 years of age after a second dose of an mRNA vaccine. Most cases have been mild and resolved quickly.

New Canadian and international data suggest the risk of myocarditis following vaccination with a COVID-19 mRNA vaccine is lower with the Pfizer-BioNTech Comirnaty vaccine (30 mcg) compared to the Moderna Spikevax vaccine (100 mcg), particularly after a second dose in males 12 to 29 years of age.

Based on new evidence, and in order to further minimize the rare risk of adolescents and young adults experiencing myocarditis and/or pericarditis after receiving a COVID-19 mRNA vaccine, NACI now recommends the Pfizer-BioNTech Comirnaty mRNA vaccine (30 mcg) is preferred for use in adolescents and young adults 12 to 29 years of age.

Based on clinical judgement, the Moderna Spikevax vaccine (100 mcg) may be considered for adolescents and adults 12 to 29 years of age who are moderately to severely immunocompromised given new evidence that the Moderna Spikevax vaccine (100 mcg) may have a slightly higher vaccine effectiveness and may provide longer protection against infection and severe COVID-19 outcomes compared to the Pfizer-BioNTech Comirnaty vaccine (30 mcg).

Informed consent should include a discussion about the rare risk of myocarditis and/or pericarditis following immunization with an mRNA vaccine. Individuals should be advised of the symptoms of myocarditis/pericarditis and to seek immediate medical attention should symptoms develop.

As a precaution, people who experienced myocarditis and/or pericarditis after a first dose of an mRNA vaccine should wait to get their second dose until more information is available. Individuals who have a history of myocarditis unrelated to mRNA COVID-19 vaccination should consult their clinical team for individual considerations and recommendations. People previously diagnosed with myocarditis but who are no longer being followed by a medical professional for heart issues should receive the vaccine.

Additional dose of COVID-19 vaccine in moderately to severely immunocompromised individuals following a primary series
Evidence to date shows that some people who are immunocompromised have a lower immune response to COVID-19 vaccines compared to the general population. Recent studies show that some people who are moderately to severely immunocompromised who did not respond to or who had a reduced immune response after two doses of an mRNA vaccine can have an increased immune response after a third dose of an mRNA vaccine.

NACI recommends that people in the authorized age group who are moderately to severely immunocompromised should receive an additional dose of an authorized mRNA vaccine following their primary series. People who are moderately to severely immunocompromised who have not yet been vaccinated should receive three doses of an authorized mRNA vaccine as their primary series. An additional dose, or a 3-dose primary series, provides another opportunity for these individuals to develop a better immune response.

Even after an additional dose, people who are immunocompromised may have reduced protection; therefore, it is recommended that they continue to follow personal public health measures and that their close contacts, including household contacts and healthcare workers, receive a primary COVID-19 vaccine series to help to protect them.

Guidance on booster doses
A complete COVID-19 vaccine series continues to provide excellent protection against serious illness for most people. Over time, some people may be less protected against serious illness, such as older adults. However, recent evidence suggests vaccine effectiveness against infection with SARS-CoV-2, the virus that causes COVID-19, is decreasing over time following completion of the primary series.

A booster dose could help restore protection against infection that may have decreased over time. Clinical trial data show that a booster dose of an mRNA COVID-19 vaccine produces a robust immune response and has a favourable safety profile comparable to the second dose of the primary series. Real-world data suggest that a booster dose of mRNA COVID-19 vaccine provides very good short-term effectiveness against SARS-CoV-2 infection. Long-term effectiveness of booster doses will continue to be monitored.

After reviewing the recent evidence and the evolving COVID-19 pandemic in the Canadian context, NACI strongly recommends a booster dose of an mRNA COVID-19 vaccine should be offered at least 6 months after the completion of a primary series to:

• adults 50 years of age and older;
• long-term care residents and seniors living in other congregate settings;
• people who received two doses of the AstraZeneca Vaxzevria/COVISHIELD vaccine or one dose of the Janssen vaccine;
• adults in or from First Nations, Inuit and Métis communities; and
• all frontline healthcare workers who have direct in-person contact with patients.

Booster vaccine programs in Indigenous communities should be determined by Indigenous leaders and communities with health care and public health partners.

NACI also recommends that a booster dose of an authorized mRNA COVID-19 vaccine may be offered to adults 18 to 49 years of age at least 6 months after completion of a primary COVID-19 vaccine series with consideration of jurisdictional and individual risks.

Pregnant and breastfeeding adults and adults who are moderately to severely immunocompromised who have received a three-dose primary series are included in those who may receive a booster dose.

If offering the Moderna vaccine as a booster (which normally is 50 mcg per dose), the 100 mcg dose may be preferred for adults who are moderately to severely immunocompromised, as well as adults living in long-term care for seniors or other congregate living settings that provide care for seniors based on the discretion of healthcare providers.

For people 18 to 29 years of age who are receiving a booster dose of an mRNA vaccine, the use of the Pfizer-BioNTech booster dose (30 mcg) may be preferred over the use of the Moderna booster dose (50 mcg) due to lower reported rates of myocarditis and pericarditis with Pfizer-BioNTech. A booster dose should be provided at least 6 months after the completion of a primary vaccine series.

The difference between a booster dose and an additional dose for people who are immunocompromised
An initial vaccine series is considered to be the number of vaccine doses needed to develop a strong initial immune response. The general population, including older adults, develops a robust immune response to COVID-19 vaccines. In Canada, a primary vaccine series is two doses of the Comirnaty, Spikevax and Vaxzevria/COVISHIELD vaccines (or any combination thereof) or one dose of the Janssen vaccine.
People who are immunocompromised may have a reduced immune response to COVID-19 vaccines. In this case, an additional dose provides another opportunity for these individuals to develop a better initial immune response.
A booster dose is used to boost the immune system when protection from a primary vaccine series begins to wane over time.
Co-administration of COVID-19 vaccines with other vaccines
For adults and adolescents over 12 years of age, NACI now recommends that COVID-19 vaccines may be given at the same time as, or at any time before or after, other vaccines.

After reviewing the evolving evidence on COVID-19 vaccines and considering the extensive data and experience of giving other routine vaccines at the same time or within days of each other, NACI has determined that a precautionary approach is no longer necessary. No specific safety concerns have been identified when routine vaccines are given at the same time or within days of each other.

Allowing COVID-19 vaccines to be given at the same time as or within days of other routine vaccines will help facilitate the rollout of the 2021 influenza vaccine program in the fall and winter and will make it easier for individuals to receive other routine vaccines they may have missed due to the pandemic.

At this time, NACI recommends that children receive the Pfizer-BioNTech COVID-19 vaccine (10 mcg) at least 14 days before or after another vaccine. This is a precaution to help to determine if a side effect that may arise is due to the COVID-19 vaccine or another vaccine. There may be circumstances when a dose of a COVID-19 vaccine and another vaccine need to be given at the same time – a healthcare provider can help with this decision.

Vaccine Interchangeability
NACI continues to recommend that the same mRNA vaccine administered for the first dose in a primary series be offered for the second dose. If the same mRNA vaccine is not readily available, or the vaccine administered for the first dose is unknown, another mRNA vaccine can be considered interchangeable and should be offered to complete the vaccine series.

An mRNA vaccine is preferred as the second dose for individuals who received a first dose of the AstraZeneca/COVISHIELD vaccine. Results from German studies suggest a potentially better immune response, including against variants of concern, when a first dose of the Vaxzevria vaccine is followed by a second dose of the Comirnaty vaccine compared to two doses of the Vaxzevria vaccine. Evidence continues to suggest a mixed vaccine schedule has a good safety profile. Receiving an mRNA vaccine as a second dose also mitigates the potential risk of Vaccine-induced Immune Thrombosis Thrombocytopenia (VITT) associated with viral vector vaccines.

Key Facts
• The National Advisory Committee on Immunization (NACI) is an external body of experts that provides recommendations to the Public Health Agency of Canada on the use of authorized COVID-19 vaccines to support provinces and territories in planning COVID-19 vaccines programs in Canada.