It is generally very safe for your mother to get vaccinated. Hisone (hydrocortisone) at a 5mg daily dose is a very low dose that typically does not weaken the immune system or make vaccines unsafe. In fact, keeping her vaccinations up-to-date is highly recommended to protect her health. Please ensure she does not stop or alter her Hisone dosage before getting vaccinated, as her body relies on this medication daily. I recommend a quick discussion with her doctor to confirm her specific vaccine schedule, but you can feel highly reassured that her low-dose medication should not prevent her from being safely vaccinated.