Short and simple. There is one reason that an observational vaccine safety trial would be stopped “early.” Stopping a trial early removes the risk of liability when the vaccine is likely to cause serious harm and injury or not work in the real world.
If the coronavirus vaccine trial was to continue it could reveal serious harms caused by the vaccine. So that said, the real “benefit” of stopping a trial is because if any harm were seen then the vaccine couldn’t come to market. Or if they saw someone being harmed and still brought the vaccine to market then the manufacturer or the government would be legally liable for those injuries and harms that they KNEW would happen.
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Fauci says coronavirus vaccine trials could be stopped early if they produce good results