Toronto 
Ontario’s Chief Medical Officer of Health Dr. Kieran Moore announced today that immunocompromised residents are eligible for a fourth dose of COVID-19 vaccine starting tomorrow.
All immunocompromised individuals can book appointments for a fourth dose, as long as, if at least three months, or 84 days, have passed since their third dose.
Immunocompromised individuals include those undergoing chemotherapy, recipients of solid-organ transplant, those who are taking immune-suppressing medication, among other groups.
Unlike the general population, where a two-dose series of mRNA vaccine is considered as primary vaccine series, moderately to severely immunocompromised is recommended a three-dose primary series. Hence the fourth dose is the booster dose for this section of the population.
Ontario, on December 19th, started administering a fourth dose of COVID-19 vaccine to residents of long-term care homes, retirement homes, Elder Care Lodges and other congregate care settings.
The province is also making a third dose of COVID-19 vaccine mandatory for all staff, students, volunteers, caregivers and support workers of long-term care settings by January 28, 2022. Proof of a booster dose will also be required for all visitors currently eligible for a booster once the temporary pause on general visitors is lifted.
