In your hypothetical case, the treatment is beneficial both for society and for the patient. On the other hand, if there is a 1 in 100 chance of a side effect versus a 1 in 1000 chance of getting a debilitating disease, the vaccination may not be good for the patient. But if the chance of getting the debilitating disease would be 1 in 10
without herd immunity, then the vaccination is good for society.
It's just that most of the benefits of the vaccination flow not to the patient but to the other people they don't infect, and transitively.
This varies a lot by vaccine. The typhoid-fever vaccine I took in 2003 has "trivial side effects" in the 90-in-100 range, I think --- namely, you feel sick for a few days.
You're absolutely right, I should have been more specific by saying that in the case of the MMR vaccine, trivial side effects are in that lower range, but --as you've pointed out-- that isn't true in all vaccines.
In your hypothetical case, the treatment is beneficial both for society and for the patient. On the other hand, if there is a 1 in 100 chance of a side effect versus a 1 in 1000 chance of getting a debilitating disease, the vaccination may not be good for the patient. But if the chance of getting the debilitating disease would be 1 in 10 without herd immunity, then the vaccination is good for society.
It's just that most of the benefits of the vaccination flow not to the patient but to the other people they don't infect, and transitively.