Archived 19: Summary of National Advisory Committee on Immunization (NACI) rapid response: Additional dose of COVID-19 vaccine in immunocompromised individuals following a 1- or 2-dose primary series

Publication date: September 10, 2021

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• Overview
• What you need to know
• Quotes

Overview

• On September 10, 2021, the Public Health Agency of Canada (PHAC) released updated advice from the National Advisory Committee on Immunization (NACI) regarding an additional dose of a COVID-19 vaccine in some immunocompromised individuals following a 1- or 2-dose primary series. These recommendations are based on current scientific evidence and NACI's expert opinion.
• A primary vaccine series is generally considered to be the number of initial doses of vaccine given to induce an immune response and provide initial protection. This is different from a “booster” dose, which is used to boost the immune system when protection from a primary vaccine series shows signs of waning over time.
• The general population develops a robust immune response to COVID-19 vaccines. For the general population, a primary vaccine series is two doses of the Pfizer-BioNTech, Moderna or AstraZeneca/COVISHIELD vaccines (or any combination thereof) or one dose of the Janssen vaccine.
• Immunocompromised individuals have a weakened immune system due to disease or treatment. Evidence to date shows that some immunocompromised individuals have a lower immune response to COVID-19 vaccines compared to the general population.
• Recent studies show that some individuals 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.

After reviewing the evidence, NACI recommends that:

• 1. For those who have not yet been immunized, moderately to severely immunocompromised* individuals in the authorized age groups should be immunized with a primary series of three doses of an authorized mRNA vaccine.
• 2. For those moderately to severely immunocompromised* individuals in the authorized age groups who have previously received a 1- or 2-dose complete primary series, including those who received a mixed vaccine schedule, should be offered an additional dose of an authorized mRNA COVID-19 vaccine.
  • 2a. An additional dose of a viral vector vaccine should only be considered when other authorized COVID-19 vaccines are contraindicated or inaccessible. Informed consent for an additional dose of a viral vector vaccine should include discussion about the lack of evidence on the use of an additional dose of viral vector COVID-19 vaccine in this population.

*For this recommendation, moderately to severely immunocompromised includes individuals with the following conditions:

• Active treatment for solid tumour or hematologic malignancies   
• Receipt of solid-organ transplant and taking immunosuppressive therapy
• Receipt of chimeric antigen receptor (CAR)-T-cell therapy or hematopoietic stem cell transplant (within 2 years of transplantation or taking immunosuppression therapy)
• Moderate to severe primary immunodeficiency (e.g., DiGeorge syndrome, Wiskott-Aldrich syndrome)
• Stage 3 or advanced untreated HIV infection and those with acquired immunodeficiency syndrome
• Active treatment with the following categories of immunosuppressive therapies: anti-B cell therapies (monoclonal antibodies targeting CD19, CD20 and CD22), high-dose systemic corticosteroids (refer to the Canadian Immunization Guide for suggested definition of high dose steroids ), alkylating agents, antimetabolites, or tumor-necrosis factor (TNF) inhibitors and other biologic agents that are significantly immunosuppressive.

To see the full update, please visit NACI rapid response: Additional dose of COVID-19 vaccine in immunocompromised individuals following a 1- or 2-dose primary series.

What you need to know

• Evidence to date shows that some immunocompromised individuals, including those receiving immunosuppressive therapies, may have a lower immune response to COVID-19 vaccines compared to the general population.
• People who are immunocompromised due to disease or treatment are also at increased risk for prolonged infection and serious complications from COVID-19.
• NACI has reviewed new evidence from recent studies on the safety and immune responses of an additional dose of a COVID-19 vaccine in immunocompromised individuals who had previously received two doses of a COVID-19 vaccine. When developing this recommendation, NACI also reviewed a report on the ethical considerations of offering an additional dose to individuals who are immunocompromised completed by the Public Health Ethics Consultative Group at PHAC. An additional dose contributes to health equity by providing another opportunity for immunocompromised individuals to develop a better immune response which could offer better protection against COVID-19.
• Recent studies show that some individuals 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. No safety concerns were identified in these studies.
• After reviewing the latest evidence, NACI now recommends that individuals in the authorized age group who are moderately or severely immunocompromised:
  • should receive three doses of an authorized mRNA vaccine if they have not yet been immunized; or
  • should receive an additional dose of an authorized mRNA vaccine if they have previously received a 1- or 2-dose primary series, including those who received a mixed vaccine schedule.
• For this recommendation, moderately to severely immunocompromised includes individuals with the following conditions:
  • Active   treatment for solid tumour or hematologic malignancies   
  • Receipt of solid-organ transplant and taking immunosuppressive therapy
  • Receipt of chimeric antigen receptor (CAR)-T-cell therapy or hematopoietic stem cell transplant (within 2 years of transplantation or taking immunosuppression therapy)
  • Moderate to severe primary immunodeficiency (e.g., DiGeorge syndrome, Wiskott-Aldrich syndrome)
  • Stage 3 or advanced untreated HIV infection and those with acquired immunodeficiency syndrome
  • Active treatment with the following categories of immunosuppressive therapies: anti-B cell therapies (monoclonal antibodies targeting CD19, CD20 and CD22 ), high-dose systemic corticosteroids (refer to the Canadian Immunization Guide for suggested definition of high dose steroids ), alkylating agents, antimetabolites, or tumor-necrosis factor (TNF) inhibitors and other biologic agents that are significantly immunosuppressive.
• For individuals who have already received a 1- or 2-dose primary series, the minimum interval between the first vaccine dose (if Janssen) or second vaccine dose (if Pfizer-BioNTech, Moderna, AstraZeneca/COVISHIELD) and an additional dose should be 28 days. A longer interval between the last dose of an initial primary vaccine series and an additional dose is likely to result in a better immune response. However, waiting for a longer interval before administering an additional dose may leave immunocompromised individuals with less protection against COVID-19 during that time. Risk factors for exposure and severe disease should be considered when deciding on the appropriate interval.
• Even after an additional dose, people who are immunocompromised may still have a reduced protection. Therefore, it is recommended that individuals who are immunocompromised continue to follow recommended personal public health measures and that their close contacts, including household contacts and healthcare workers, receive a COVID-19 vaccine to help to protect the immunosuppressed person.
• It is important to distinguish between a 3-dose primary series for immunocompromised individuals and booster doses for the general population.
  • A primary vaccine series is considered to be the number of vaccine doses needed to develop a complete and robust immune response. As immunocompromised individuals may have a reduced immune response to COVID-19 vaccines, an additional dose provides another opportunity for these individuals to develop a better immune response, completing their primary series.
  • The general population develops a robust immune response to COVID-19 vaccines. For the general public, a primary series is two doses of the Pfizer-BioNTech, Moderna, or AstraZeneca/COVISHIELD vaccines (or any combination thereof) or one dose of the Janssen vaccine. Booster doses may eventually be needed for specific populations and/or the general population if protection from a 1- or 2-dose primary vaccine series shows signs of waning. Studies on how long protection from a 1- or 2-dose series lasts in the general population and on the potential need for booster doses are ongoing.
• Guidance on the use of booster doses for specific populations, such as long-term care residents, is being considered by NACI. NACI will continue to monitor the evidence regarding the need for and effectiveness of booster doses for specific populations and the general population and will update guidance as required.
• NACI will be continuing to monitor the safety and effectiveness of COVID-19 vaccines in individuals who are immunocompromised and will update recommendation as needed.

To see the full update, please visit NACI rapid response: Additional dose of COVID-19 vaccine in immunocompromised individuals following a 1- or 2-dose primary series.

Quotes

“NACI has carefully reviewed the available data, including an assessment of benefits and harms of an additional dose, and have recommended that moderately or severely immunocompromised individuals who may have somewhat lower responses to their first vaccinations should receive a three-dose primary vaccine series using mRNA COVID-19 vaccine for the additional dose. This is not unusual for immunocompromised groups, where we often recommend different vaccine schedules to help them achieve better protection.  This is different from a booster dose, which would be used to boost an immune response that has waned over time.  NACI is also looking at whether booster doses might be needed for some key populations, but it is too early to comment on the state of the evidence for general boosters at this time.”

- Dr. Shelley Deeks, NACI Chair

“Individuals who are moderately or severely immunocompromised, including those receiving immunosuppressive therapies, are more likely to have a lower immune response to only two doses of COVID-19 vaccines. An additional dose of vaccine will increase the immune response to the COVID-19 vaccines which is expected to result in better protection. However, even with a third dose of vaccine, protection from SARS-CoV-2 infection may be lower for people with problems with their immune system. Therefore, in addition to receiving an additional dose of a COVID-19 vaccine, immunosuppressed individuals should continue to follow public health precautions such as wearing a mask. Their family and other close contacts should also be sure to receive their COVID-19 vaccine so they don’t spread infection to the immunosuppressed person.”

- Dr. Theresa Tam, Chief Public Health Officer