The way these studies (most of the big trials finishing up soon, and this one too) are set up is that they measure the percentage of people that will not get sy

The way these studies (most of the big trials finishing up soon, and this one too) are set up is that they measure the percentage of people that will not get symptomatic covid-19, so the only thing that is measured is whether they get symptoms or not. So the result is that 90% (within a confidence interval) of people who are given this vaccine will not develop any covid symptoms. Transmission may be impacted, and the data will reveal hints about this, but it's impossible to draw hard statistical conclusions about that, and in general a different type of vaccine technology will be needed to end transmission and thus the pandemic. This will save countless lives though, and may end lockdowns, so a great day nonetheless.