I don't know, but it'll take ages to restore cold resilience. Took about 5 years for me.

I think covid might be damaging RNA, or the mitochondrium, or somehow stops the cell from being able to gather energy. Maybe it has something to do with the increased production of lipids and hyaluronic acid which has been described in some reports. Maybe it damages the thyroid. IDK. I hope to find out one day.