Should Vancomycin Be Continued After Cauterization?

My 4 year old son has a long history of illness since he was 7 months old. He is not getting better and has been much worse since his last surgery for tubes and cauterization of the lower turbinates. He has been treated with vancomycin twice now and it seems to be the only medicine he reacts to. Just recently we got back some bad blood tests (high white blood cell counts, really high platelet counts, normal range red blood cells, high MCV, High Lymphs absolute, high monocytes absolute, immunoglobulin is low. We are waiting on approval from our insurance to get immunoglobulin infusions done on our son. We do not have a diagnosis other than they say his immune system is low. Any thoughts of what could be going on? We are really worried!