Children ages 5 to 11 who are "moderately to severely" immunocompromised should receive a third dose of the COVID-19 vaccine, according to Canada's immunization advisory body.

In a , the National Advisory Committee on Immunization (NACI) says that Canada is now in a fifth wave of the pandemic, driven by the highly transmissible Omicron variant.

The agency says that while the risk of serious outcomes for children who become infected with COVID-19 is still low, there is a rising number of children who are being hospitalized with serious symptoms as a result of the virus.

It recommends immunocompromised children receive a third dose of the vaccine four to eight weeks after their second dose.

NACI says it reviewed what is known about the Omicron variant, as well as "new and reassuring real-world safety data" on the use of Pfizer-BioNTech booster shots in children, when considering the new recommendation.

According to the statement, "moderately to severely immunocompromised" would include children 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 two years of transplantation or taking immunosuppression therapy)
  • Moderate to severe primary immunodeficiency with associated humoral and/or cell-mediated immunodeficiency or immune dysregulation
  • HIV with prior AIDS defining illness or prior CD4 count ≤ 200/mm3 or prior CD4 fraction ≤ 15% or perinatally acquired HIV infection
  • 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

NACI’s current recommendation for children who are not "moderately to severely" immunocompromised is two doses of the Pfizer-BioNTech vaccine, four to eight weeks apart.