So I'm posting on mobile and can't find the link, but there was a literature review posted on reddit a month or two ago. It was a collection of some 1-2 dozen p

So I'm posting on mobile and can't find the link, but there was a literature review posted on reddit a month or two ago. It was a collection of some 1-2 dozen papers regarding smoking and risk of infection for COVID19 as well as SARS and MERS. What was clear from multiple papers was that smokers were significantly less likely than the general population to test positive for these viruses, though their infections may be more severe. There is published evidence that nicotine may downregulate ACE2 receptors - which means fewer binding sites for potential infection. I have a related pet theory that vaping may be doubly protective, considering that some 60 years ago, propylene glycol was used as a surface disinfectant. Since vape juice is some 30-70% PG, and because the virus infects lung cells at the interface between air and blood, I'd bet good money that PG may have an effect in reducing viral load, at least prophylactically. That's in addition to the ACE downregulation, though we don't really know how long and how much vaping one needs to do to see any benefit, if there is one...