I agree that adverse affects are not the normal response but I strongly disagree with your use of the term "rare". One in a hundred would qualify as uncommon; one in a thousand might be considered rare. I am a firm believer in informed consent and that is not possible when people sugarcoat the reality. Medical practitioners do that enough; we do not need to belittle the agony of those who suffer from the adverse effects,

There is one fallacy in comparing the effects to those of a placebo; intensity of reaction is not included. A placebo might give someone a minor headache but the medication might send them to an ER for a throbbing headache. Both might be counted simply as a headache.

We can not and should not dismiss the reality of those who suffer disabling consequences.

And it is important to know what might occur even if most people do not experience it. Knowing I might experience light-headness may mean I should not engage in any activity where falling could have serious consequences.

BTW, I have a true rare reaction to vitamin B-12. It is water soluble and any excess is supposedly excreted through urine. Someone forgot to inform my body of that and it holds on to the B-12. I went from being deficient to the value being off scale with a daily supplement. MY PCP had wanted me on weekly injections.