Two papers exploring the possibility that previous exposure to other coronaviruses like the common cold may provide some immunity to Covid 19.
These are not peer reviewed yet, but if true, it could explain why a lot of the models were drastically wrong, and why outbreaks in countries all over the world seem to follow a similar pattern. Some curves are flatter than others, but they all seem to go up rapidly, then peak and start to slowly go down, usually over a period of 70-80 days.
This research also is also good news for vaccine development.
https://www.biorxiv.org/content/10.1...414v1.full.pdf
https://www.cell.com/action/showPdf?...2820%2930610-3