[corty]

I didn't read the original study, but I think the 75 to 95% reduction is in the number of cases, not in viral load. So this would be, in other words, a 75 to 95% prevention.

As to the time the immunity lasts, that remains to be seen. Since it is brand-new, we will only know when new cases from previously-vaccinated people pop up. Maybe it'll be yearly, maybe a booster every 10 years, maybe lifelong. There is research showing that the antibodies from a corona infection last about half a year, but that is not the only factor that may provide immunity. And the yearly flu shot is because the flu virus mutates very rapidly, which corona doesn't as much.