NACI Recommends a Third Dose of COVID-19 Vaccine For Some Immunocompromised Individuals

The National Advisory Committee on Immunization (NACI) is now advising an additional or third dose of a COVID-19 vaccine for some immunocompromised individuals.

NACI says based on current scientific evidence research has shown that those with a weakened immune system due to disease or treatment have a lower immune response to COVID-19 vaccines, compared to the general population.

As per the news release, “the additional or third dose being considered for moderately to severely immunocompromised persons should be distinguished from that of a booster dose.

The intent of a booster dose is to restore protection that may have waned over time in individuals who responded adequately to an initial 1- or 2-dose primary vaccine series.

Additional doses beyond the standard primary vaccine series, such as discussed in this statement, provide an opportunity for individuals who may not have achieved an adequate level of protection from the standard primary vaccine series to develop a better immune response.”


As per NACI, moderately to severely immunosuppressed 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, alkylating agents, antimetabolites, or tumor-necrosis factor (TNF) inhibitors and other biologic agents that are significantly immunosuppressive.

Many provinces including Alberta, Ontario, Quebec were already providing a third dose to the immunocompromised and those who live in high-risk settings like congregate care facilities.

Alberta, Saskatchewan and Quebec are also offering up to two additional doses to those who received mixed doses or AstraZeneca/Covishield vaccines.


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