> Rather, it means the risk of infection among vaccinated people was 90 percent lower than the risk among unvaccinated people.

OMG that's the second time I encounter this nonsensical formulation, people in media just repeat stuff (big surprise /s) without understanding it. It makes no sense to say "number A is 90% lower than number B". Language of percentages is not supposed to be used this way.

What that result means is that given equal number of vaccinated and unvaccinated people, estimate of number of vaccinated people who got saved from infection per one day is 90% of the number of unvaccinated people who got infected per one day. In other words, not knowing other factors, a vaccinated person has 10x lower chance of getting infected than an unvaccinated person.