Is a common cold or the flu likely to reduce affect immune system sufficiently to allow the recurrence of a head/neck cancer?

No: Having a cold does not reduce the immune system. In fact, the whole problem with the common cold is that it is a disease in which the immune system over-enthusiastically attacks a mild virus, causing all of the miserable symptoms we know and love. If anything having a cold is a sign of a robust immune system and shouldn't have any implications with head or neck cancer.

No: No prrof over time to show any relationship of htis.

No: The immune system is more likely to be affected by chemotherapy than by a cold or the flu.