I suspect your nurse may well be wrong. She is probably thinking of the fact that we are supposed to be immunocompromised when on steroids, particularly high doses. But she has it the wrong way round - you are MORE in need of the flu vaccine because you will have more difficulty in fighting the flu if you get it. It is a common mistake.
Being on pred does mean that you may not develop an immune response as efficiently - but since the flu vaccine is a dead vaccine there is no risk if you are given it of developing real flu. The vaccine trains your immune system to recognise the bugs in advance - so it knows what it is looking for in the real situation - like training teaches medics to recognise diseases.
A study was done in children with asthma on high dose pred and the conclusion was this:
"The authors conclude that high-dose prednisone therapy does not diminish the effectiveness of the influenza vaccine in children with asthma. Because the vaccine does not exacerbate asthma symptoms and, in fact, provides a protective immunologic response, physicians should administer the vaccine concurrently, when indicated, to children who are undergoing treatment of acute asthma."
As I explained to tavidu, the flu jab prepares you for a possible infection in a safe way. Being on pred does mean you may struggle a bit to develop your own immunity once you meet the flu for real - because it isn't a "dead" form. You MUST NOT HAVE THE LIVE FORM - this is now available as a nose-spray for children - but the jab is no problem.
The Joint Committee on Vaccination recommends vaccination for patients in various groups and we come under this one:
"Immunosuppression
Immunosupression due to disease or treatment.
- Patients undergoing chemotherapy leading to immunosuppression.
- Asplenia or splenic dysfunction.
- HIV infection.
- Individuals treated with, or likely to be treated with, systemic steroids for more than a month at a dose equivalent to prednisolone at 20 mg or more per day (any age) or, for children under 20 kg, a dose of 1 mg or more per kg per day.
Some immunocompromised patients may have a suboptimal immunological response to the vaccine."
I think you should speak to your doctor and possibly the nurse should be told not to give out incorrect information - it could be putting people at risk.