Chemo is given to you after you have a super deadly disease, cancer. Unless you take chemo you are dead in a very short time so you very little to lose and a lot to gain . https://en.wikipedia.org/wiki/Hail_Mary_pass

Wow, you don't say! I had no idea.

There's no shame in not knowing everything

I'm being sarcastic. Everyone knows that...

Far more people are exposed to vaccines than chemotherapy drugs.

And this refutes my point...how exactly?

Not every comment in a discussion needs to be nor is intended as a direct refutation. Sometimes people add additional relevant comments for consideration.

In this case, a treatment that is going to be given to 10-100K times as many people, most of whom are not suffering from an acute, life-threatening condition at the time of treatment, has a much different threshold for weighing the risks of possible harm.

A cancer treatment which cured 999 of 1000 patients and killed the 1000th outright would be a major breakthrough. A flu vaccine that did the same would rightly be rejected.