Hello, numbers. Every infection has an R0 rate (average number of people infected by a single infected person). If it's greater than 1, the infection spreads e

Hello, numbers. Every infection has an R0 rate (average number of people infected by a single infected person). If it's greater than 1, the infection spreads exponentially. If it's lower than 1, it peters out. Vaccinating X% of people pushes R0 lower by X * N, where N depends on mutation rate, how good is the vaccine at preventing the spread (vs. reducing symptoms), etc. R0 is also affected by seasonality, immunity from earlier infections, etc. Polio doesn't mutate as fast, the vaccine lasts long time, and prevents both symptoms and the spread. R0 drops below 1, polio defeated. COVID mutates much faster, has one of the highest R0 rates among known diseases, vaccine lasts a limited time, considerably reduces mortality rate (which isn't much of a concern for fit healthy adults under 50), and somewhat reduces the spread. It pushes the R0 number somewhat down, but not below 1. What actually ended the pandemic was the Omicron variant that mysteriously grew much faster in the upper respiratory tract, and got your body to start fighting it before it did anything to the lungs. It still has enough R0, but the symptoms are so mild, it became mostly indistinguishable from common cold, so people stopped caring. Had we vaccinated the at-risk groups, and given strong incentives for others to lose weight and start exercising, we could have arrived at the same, or lower death toll with much less taxpayer money going towards the Big Pharma.