Few data are available on cats receiving tumour chemotherapy, but studies in dogs suggest that that chemotherapy might not have a significant impact on immunologic reactions and the ability to mount antibody responses and that administration of chemotherapy does not preclude the administration of vaccines. However, based on the recommendations in humans, when tumour chemotherapy is being considered, vaccination should ideally precede the initiation of chemotherapy or immunosuppression by at least two weeks or, if not possible, be postponed until at least three months after the end of chemotherapy. If possible, vaccination during chemotherapy should be avoided because antibody responses might be suboptimal.