Alright so I'd like you to draw me a picture of your reasoning behind the statement that we do not know how long immunity from infection lasts but we have a bet

Alright so I'd like you to draw me a picture of your reasoning behind the statement that we do not know how long immunity from infection lasts but we have a better idea with the vaccines. Because in the world I live in, we have had infections longer than vaccines, which means more data on immunity from infections than vaccines. Where did you get that statement from and why did you say it?