It was written about here a while back that there was pretty good evidence that 80% of the population had some preexisting, natural resistance to Covid. It seemed to explain the Diamond Princess ship having such a low % of infected passengers despite them being older and presumably more susceptible.

Im wondering how the efficacy numbers being reported in Israel can be so low. If a total vaccine failure meant only 20% of the population could potentially be infected, how were they reporting efficacy numbers as low as 16%, or even 60%? Seems like ~80% should be the lowest efficacy number they should see, even if the shots are a complete failure. Unless, of course, the shots do something to compromise that 80% pre-existing natural protection.

Has anyone seen any recent data lately that would help explain this?