I use sambucol when I catch a virus. Love the stuff. I also drink the effervescent tablets as a drink. The tablets are lower dose, so more of a preventative than a treatment.
Is there any reason why your immune system may be compromised at the moment? I know there are many reasons that this could be. When I started working in a university I caught every bug going. All the students used to bring them in and spread them round til no one was bug free for months at a time. And I understand it, the same thing happens to teachers, or people who work shops...
Might be worth discussing it with your doctor, if you haven't got a reason like that for catching so many bugs.
Having said that, raised blood glucose also compromises the immune system. Do you self-test? And if so, what range does your blood glucose run at? If you are running high, then adjusting diet or meds may bring things back into line...?
Hope that helps.