Now Guardian published an article about it, there are people who are immune, due to their already existing T-cells:
https://www.theguardian.com/world/2021/nov/10/people-exposed-to-covid-yet-not-falling-ill-may-have-immune-memory-finds-study
As I wrote here  >>/44218/ that Hungarian researcher said there were papers. The video was from 2020 September or so. Weird how The Guardian could only find such paper just now.