You should take along the completed referral letter or an equivalent letter issued by your medical scheme at a vaccination site, as well as your ID and medical scheme details (if available). The referral form /  Annexure A: Covide-19 Vaccination: Request for administration of an additional dose can be found on the following link: https://sacoronavirus.b-cdn.net/wp-content/uploads/2021/11/circular-form.jpg 


You can also take the vaccination code for the additional dose if you are able to register online https://vaccine.additional.health.gov.za/#/


More information is given in this circular https://sacoronavirus.co.za/2021/11/29/circular-vaccination-of-immunocompromised-adults/