I have just read Jim's post about his wife now on 5mg prednisone and reducing having had Actemra.
I am in a similar position having been diagnosed with large vessel GCA in November 2017 although with symptoms for at least 9 months prior to that. I too am down to 5mg prednisone ( I was on 100mg daily over November and December!) and have reduced so far with no ill effects or flares whatsoever to 5mg for the past month. My Rheumatologist has said he will have me off prednisone altogether by the end of the year after 7 monthly infusions of Actemra.
When I questioned this he told me that Actemra facilitates reducing pred but now I am wondering if I should taper at a slower level?