There are random bits of correlation everywhere and investigating whether there's an underlying causative reason is laborious. It's no surprise then that not ev

There are random bits of correlation everywhere and investigating whether there's an underlying causative reason is laborious. It's no surprise then that not every one gets looked at, and people pick what is most likely to yield an interesting result. In this case IMO it'd be quite surprising if smoking actually impeded any virus. I don't think it's a conspiracy that this isn't getting attention. Other commenters have listed some possible confounding variables here, but the first one that popped into my mind is that people who know they have a higher risk from past smoking are more likely to be cautious and not get exposed. This is true for one of my relatives with COPD who was very careful to not get it before vaccines were available.