Immunological insights on influenza infection and vaccination during immune checkpoint blockade in cancer patients

Cancer patients undergoing immune checkpoint blockade represents a new population still to be investigated from the immunological viewpoint. The complex modifications occurring in the immune responses of these individuals against noncancer antigens are largely unknown and they potentially influence the oncological outcome. The intentional introduction of vaccinal antigens could contribute, as a further exogenous immunological stimulus, to shift the balance between tolerance and activation, likely influencing both the tumor context and the complex relationships between the tumor and the host. Moreover, the effect of exogenous wild stimuli such as viral or bacterial infections may likely contribute to the immunological ensemble, even potentially interfering with the immune escape from antitumor response. In conclusion, the cancer patient treated with ICI can no longer be considered like the entire cancer population undergoing chemotherapy or targeted therapy, since the target of ICI is no longer represented by the tumor, but instead by the immune system [35]. Considering this crucial paradigm, the assumptions adopted up today with regard to concomitant medications, vaccinations, true risks from viral or bacterial infections, should be completely discarded and rewritten for this special cancer patient population.