You've listed the main side effects of the treatment: pain, fever, and delirium.

About 20-30 minutes after receiving a dose of IL-2 by infusion, my body would undergo violent bed-shaking rigors for 10-20 minutes. I had the worst chills I've ever had, followed by breaking out in a hot sweat when it had passed. This was very unpleasant.

After each successive dose, the effects would worsen.

Essentially, the doctors were trying to take my body to the brink of experiencing a cytokine storm (https://en.wikipedia.org/wiki/Cytokine_storm) to jump-start my immune system.

This was a pretty miserable part of the treatment, but (in the end) obviously worth it.