I'm very concerned about my 1 year old cat. Since Saturday he hasn't eaten and only been out once and is very lethargic. He has barely moved all weekend which is very unlike him. He had a booster jab on Wednesday and I am wondering if it might be to do with this although the symptoms didn't start until Saturday and I would have thought they would have come quicker then that and not lasted as long. Would it be silly to take him to the vets today or shall I just see how he is tomorrow?