The article discusses the possibility that nicotine may block the coronavirus cell surface receptors but dismisses it. What I’ve read about this tho theorized that since the virus seems to preferentially infect endothelial tissue that longer term smokers with lung and esophageal endothelial dysplasia would be protected against infection because there was no mechanism for the virus to enter the lung tissues.

Not saying it’s true, but the mechanism they report and dismiss here is not what I’d seen as the primary hypothesis about the protectiveness that smokers were demonstrating in the referenced studies