Did you know medical certificates expire? They have an end date! So when an employer or other entity asks for a clearance certificate, this is what we are going to write:
The whole point of a medical certificate is to certify someone unwell or unfit. This is why there is a beginning date AND an end date. At the end date, the patient is no longer certified unwell/unfit. I have enclosed the negative COVID results and you will note your employees certificate has reached its end date. I further enclose professional advice from our professional organisation in regard to this. It follows that the certificate of ‘clearance’ you are suggesting is unprofessional and those who would provide one are acting similarly.
I hope this information finds you well.