Effectiveness and efficacy are two different things. How these vaccines work in the real world is yet to be seen. Here's one article with a lot of interesting comments: https://www.bmj.com/content/371/bmj.m4347/rapid-responses

Also, if I'm understanding this correctly, they only had 94 cases of Covid, out of a study group of 44000 people?! Maybe this is normal for vaccine trials, but it seems like an extremely low number of people from which to draw such important conclusions.