The pharma “efficacy” numbers are basically PR efforts. It’s the way you make stats “Lie”...:-)
Good video from a math prof explaining Absolute Risk Reduction vs. Relative Risk Reduction.
https://www.youtube.com/watch?v=e2Ue85EV2Us
Pfizer’s “95%” efficacy (Relative Risk Reduction) really means that the unvaccinated in their trial had a 0.93% incidence of covid vs. the vaccinated incidence of covid 0.046% So the Absolute Risk Reduction was 0.884%.
So that means you would have to vaccinate 113 people to keep one person from getting serious covid.
From the study it means that 95% of the total COVID-19 cases came from the Placebo group. Only 5% of the total cases were in the vaccinated group.
I believe the incidence you are talking about would be additive. Meaning if you have a 0.93% chance of catching covid (as per the study) that would be the risk over 2 or 3 months (the time study participants were given before results were published). So in any given year you would have about a 3.7% to 5% chance of catching COVID-19 if no one took a vaccine.
In densely populated areas the probability would be much greater because elevators, subways, trains, office building would be in play. The study took place in a world wide shut down. Once things go back to normal the yearly probability of catching COVID will be much higher.