On the guidance of the College of Physicians and Surgeons of Ontario (CPSO) whose mission is 'Serving the people of Ontario through effective regulation of medical doctors' there are very few reasons to grant medical exemptions from COVID vaccination.
To quote the CPSO on this topic:
"Generally speaking, there are very few acceptable medical exemptions to the COVID-19 vaccination (e.g., an allergist/immunologist-confirmed severe allergy or anaphylactic reaction to a previous dose of a COVID-19 vaccine or to any of its components that cannot be mitigated; a diagnosed episode of myocarditis/pericarditis after receipt of an mRNA vaccine)." Read full statement here.
For those who do have allergy to a component or anaphylaxis to the first dose, there are many ways for these issues to be mitigated and patients to still receive their full course of vaccination.