Ontario is making immunocompromised individuals eligible to receive a fourth dose of COVID-19 vaccine, after previously doing the same for residents of long-term care homes and other congregate care settings.

Chief Medical Officer of Health Dr. Kieran Moore made the announcement during a briefing on Thursday afternoon.

He said that beginning tomorrow morning immunocompromised Ontarians will be able to book appointments for a fourth dose, so long as they are 84 days out from their third dose.

“We already asked that severely to moderately immunocompromised individuals receive three doses as their primary series on the COVID-19 vaccine. But we are now ensuring that those who are immunocompromised can receive their fourth dose,” he said.

Immunocompromised individuals include organ transplant recipients, anyone undergoing chemotherapy and anyone who is taking immune-suppressing medication, among other groups.

Moore said that the list of immune-suppressing medications is “quite extensive” but includes drugs that are prescribed for relatively common severe illnesses, such as rheumatoid arthritis, Colitis and Crohn's disease.

“It's estimated that only 64 per cent of eligible organ transplant recipients have received even their third dose. So whether it's your third or your fourth dose, those who are immunocompromised are strongly encouraged to make an appointment and benefit from the protection the vaccine provides,” Moore said.

Ontario has been providing third doses to immunocompromised individuals as part of a “extended primary vaccine series” since August.

These are the people that fall under the category of immunocompromised, according to the Ministry of Health:

  • a transplant recipient (including solid organ transplant and hematopoietic stem cell transplants)
  • receiving stable, active treatment (chemotherapy, targeted therapies, immunotherapy) for a malignant hematologic disorder or solid tumor
  • in receipt of chimeric antigen receptor (CAR)-T-cell
  • an individual with moderate or severe primary immunodeficiency (for example, DiGeorge syndrome, Wiskott-Aldrich syndrome)
  • Stage 3 or advanced untreated HIV infection and those with acquired immunodeficiency syndrome
  • undergoing 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 or are taking specific immunosuppressant medications
  • receiving dialysis (hemodialysis or peritoneal dialysis)