Can the miximitosis injection cause the disease in your rabbit which was fine until you took it for the injection and then after a day or two got unwell?

Ofcourse after any immunisation jab the animal may get ill, as they are inected with a weak/dead/similar etc strain of the disease they are being immunised against. The rabbit should be kept in a stress-free environment for a week or two following the injection, or until he seems better. If his condition gets worse or you are still worried then you should ring/take him back to the vets.