It may even be less than 20%. Until 2020, most medical experts understood that immunity from some viruses would provide resistance to others. Our immune systems are incredible.
But when a new coronavirus that became the focus of the whole world started to spread, any sense of proportion and any historical knowledge disappeared. Only garbage models counted, even when they failed catastrophically.
If you care about the science, here’s some solid statistical analysis.
Antemodernist 