There are always requirements to become or remain a doctors patient. First you have to agree to pay his fees. Second, you have to provide the doctor a medical history. Lastly, you have follow the doctors medical advice which in this case is getting vaccinated. The doctor sent a letter to his patient stating that to continue as his patient, a vaccination is required. Patients who do no follow a doctors medical advice are routinely recharged. The only time a doctor is required to threat a person is in an emergency.
I just had an appoint today with my doctor. I ask her if she saw patients that were not vaccinated and she said yes. However she said any patient who was said no to being vaccinated was strongly urged to get vaccinated. If they continued to refuse vaccination with no medical reason, they would be discharged as patient by the clinic.