Why some don't get COVID-19 or have mild symptoms.

[Nay]

4. At the conclusion of the paper, the writers say that there is evidence that previous

exposure to certain specific cold viruses can stimulate a person's T-cells (cells that will 'remember' invading viruses and prompt a very quick bodily reaction to stop the invader) quickly enough that the person will have an asymptomatic response to COVID19 -- IOW, the virus gets beaten back before you get sick -- or the person will have only mild symptoms and then shake off the virus. They conclude by saying their results are still very speculative.

But I may be reading this incorrectly, so it's IMHO.