Karl Friston: up to 80% not susceptible to Covid-19

This is very enlightening and would explain why some regions were hit much harder than others.

The title is misleading, the thesis of this professor is that different areas have differing amounts of immunity to the virus (up to 80% in SOME places), i.e, they had already built up T-cell resistance to similar Corona viruses.

He also shows the growth was never exponential meaning the most places had some immunity, but it isn't 80% everywhere!