>> because I'm pretty sure we already have something on order of 80+% protection without a vaccine I think the way these studies are set up already accounts fo

>> because I'm pretty sure we already have something on order of 80+% protection without a vaccine I think the way these studies are set up already accounts for that. In these trials they don't vaccinate just one group and then check how many people still got sick ('only 10% got sick so it 90% effective'), but instead they split the participants into a 'vaccinated' group and a 'placebo' group (double blind), then wait until X people in the total of all participants get sick, then compare how many of them got the vaccin and how many got the placebo. Since the total group is large, this should average out pretty much all variability in susceptibility to infection (assuming the participants are selected to include a wide range of attributes, of course). I don't know how the maths work exactly but I think the 90% claim here means that if you take the vaccine you are 90% less likely to get sick from covid compared to someone else with comparable attributes.