Well the UK is because they have been vaccinating like crazy. (as well as lockdowns,etc.)
Not sure about South Africa because they have not started vaccinating yet and have just pivoted from Astra-Zeneca to J&J which has just been approved there. I have no idea what their lockdown procedures have been.
Edit: Checking on Wikpedia, they are pretty serious about lockdowns, etc. Starting Dec 1st they started locking the country down. It looks like cases peaked in early Jan. They are so serious that they arrest you if you are caught without a mask.