Less severe Covid-19 associated with antibodies against seasonal coronaviruses

A quick look through the paper doesn't leave me very impressed. The data is lacking, and the categorization of the antibody assay signal is arbitrary at best.

There is also little to no information on the test. It seems that the authors did not try to actually validate it, or they did not write the results of such validation.

I wouldn't trust this study, to be honest.