The control group will not be given the vaccine, but a placebo. Clinical trials are phased. Typically you start with a very small group of people to evaluate t

The control group will not be given the vaccine, but a placebo. Clinical trials are phased. Typically you start with a very small group of people to evaluate toxicity (e.g. below treatment levels of a drug), then a slightly larger group looking for side effect, then a significantly larger group looking for desired effects, and finally a broad group looking for safety and efficacy.