Further, once you have an effective treatment, placebo controlled trials become unethical. You must compare your new treatment to the current standard of care.
[0] https://www.nejm.org/doi/full/10.1056/nejmoa2034577 (see p 2612 of attached pdf).
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.