> Ethics. It is routine to terminate a medical trial early when the results are so clear that you know you are harming the participants by continuing; Except t

> Ethics. It is routine to terminate a medical trial early when the results are so clear that you know you are harming the participants by continuing; Except that plenty of people already decided they don't want to vaccinate, so why not to ask them to participate? Of course a double-blind study would be unethical. > once you have an effective treatment, placebo controlled trials become unethical But this is a vaccine, not a treatment. And given the scale of vaccination, wouldn't it make sense to have a control group for analyzing long-term effects? Yes, I heard many times that long-term effects are "unlikely," but the tiny possibility becomes significant at scale.