If you  cannot work because of sickness, injury or quarantine, but you would otherwise be available to work, you could be eligible to receive up to a maximum of 15 weeks of EI Sickness benefits by the Government of Canada.
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If you have a private health plan that has Short Term Disability or Weekly Indemnity benefits, then you have to apply directly to that insurer.
​https://www.canada.ca/en/services/benefits/ei/ei-sickness.html

Some Employers have their own Weekly Indemnity coverage and others have a Top-Up plan that will pay the difference of the EI Sickness benefit payout to a certain percentage as per the Employer's policy.

Contact your Plan Administrator/Employer or Beneplan @ 416-863-5157 for further details.