I’ve wondered how they could reach that conclusion, unless they intentionally exposed every vaccinated test subject to the virus and then tallied up how many got sick. And they definitely didn’t do that. (I know, they compare them to a control group, but they still don’t know who was exposed to the virus in either group).
It seems a little like having the test group drink extra water everyday, and then if only 5% get sick concluding that “Drinking more water is 95% effective in preventing COVID.”