Normally flu vaccines are recommended for people on immunosupressive drugs. I've had many annual flu vaccines since being diagnosed with cerebral vasculitis in 1997. But now I can't have them, under consultant's orders. It's partly because I'm on a huge cocktail of immunosuppression drugs (now 4 immunosuppressive drugs simultaneously, and also steroids on top) so would have no hope of getting a protective immune response from the vaccine. But it's also because a few years ago the flu vaccine seems to have exacerbated my very aggressive cerebral vasculitis. We'd just got it under control again, with difficulty, then a week after my annual flu vaccine it was off again, probably triggered by my immune system's response to the vaccine (I was on far fewer immunosuppressive drugs then).
So no flu vaccines for me any more. But my husband gets a flu vaccine every year. This is allowed because he is my carer, and needs to be fit to look after me. But it also has the advantage that it protects him from getting the flu, and therefore also by extension me from catching it from him, which is particularly good since I can't get vaccine protection myself. Since I'm mostly housebound the only person I'm likely to catch flu from is my husband, so if he doesn't catch the bug in the first place ...
This year he seems to have had flu even before the vaccine season, and has been off work a lot over the last fortnight, with a flu-like infection that wouldn't go away in a hurry. He's now at the washed-out weak stage, but recovering. And I didn't catch it from him. But I rarely catch bugs from him. Despite all the massive cytotoxic drugs I'm on I still have a high white blood cell count, and seem to fare very well with opportunistic infections. Long may it continue.
Obviously each case is different. My case of being on 4 immunosuppressive drugs at once (Methotrexate, Mycophenolate Mofetil, Azathioprine and Thalidomide) and steroids as well is very unusual. People on lower cocktails are likely to get better protection from the flu vaccine. Talk to your GP and consultant for the best advice in your case on whether to get the vaccine. Normally I think it would be recommended, especially for people with additional risk factors such as lung issues.