To help keep it as blind as possible, studies sometimes use something that is better understood and gives you the side-effects you might expect if you weren't o

To help keep it as blind as possible, studies sometimes use something that is better understood and gives you the side-effects you might expect if you weren't on the placebo. Like the Pfizer COVID study used the meningitis vaccine as a placebo IIRC. edit: see another comment suggesting that control is the right term for this rather than placebo - face palm moment.