The initial chemo and radiation are for a particular and short period of time. The shots are then given in intervals long after that other treatment has ended and effectively forestalls recurrence longer and for some patients maybe permanently. With combinations the number of patients who have a longer time to live without disease and or be cured should increase.
Combinations with other immune therapies will likely also lead to new regimens which may very likely be less toxic and problematic for the health of the patient.