How do appointment reminders via SMS work?

Ideally, an effective workflow for appointment reminders via SMS goes something like this:
If the patient keeps the first appointment, a message will be sent again for the follow-up appointment. If they do not keep the appointment, a text message can be sent asking them to make a new appointment. Of course, if you offer the option to book appointments online, you can also send a link along with the text message. This also means less extra work for you and your team.
Your patient books an appointment for a vaccination and consents to receiving appointment reminders in the process. Your system triggers a reminder SMS to be sent to the patient before the first appointment. The text should include the date, time and location of the appointment. Ideally, of course, you should word this reminder as friendly as possible; after all, your patients are your customers. Especially if you send reminders for vaccination appointments, you should also mention the vaccination specifically.