Studies show that it does not work against covid. There was anectodtal evidence in 2020 that it may provide benefit so the CDC/NIH/FDA decided to study it and those studies showed that it did not.

Who knows though... what if COVID itself modifies the placebo effect making studies not worth very much? Studies have to take in account the placebo effect because the placebo effect is something very real and also understudied.... ironically.

Nobody really knows what causes the placebo effect. It is something that happens in our brains. So we need to have more studies done on the actually placebo effect itslef.

I remember psychology 101 class in college with a small pararagraph in a text book about the placebo effect. That's all.. Just a small amount of information that the placebo effect is something that needs to be included in double blind studies.