I took an antibody test early on, before vaccines were available, none detected.
If I was infected, it would have been after I was vaccinated.
But some people seem to be naturally resistant to Covid. There has been some discussion about genetic susceptibility to Covid, based on genes passed down from other races, such as Neanderthals and Denisovans.
So.... consider this: the Covid virus made the jump from animals to humans in China, so perhaps the virus evolved to better infect people of Chinese heritage, and not so much for others. That would explain why Africans were not so impacted early on, since they are the farthest from Chinese genetically. Europeans are almost as far, so may have had more resistance to infection (since people are not 100% any ethnic group, and Chinese have been in Europe since Roman times).
It is possible that the virus evolved to take advantage of chunks of the Denisovan genome in Chinese DNA. Fortunately for Thai people, their Denisovan DNA is from a different flavor of Denisovan.