Research update:
This appears, according to the study, to be the primary mode of action of Covid on the lungs.
To summarize the study, COVID infiltration inhibits STATS and causes massive overactivation of the STAT3 pathway. This causes hyperproduction of PAI-1 protein, which then binds to and activates TLR-4 receptor. This is a major inflammatory/Immune trigger pathway most familiar in seasonal allergies (those that suffer know exactly how bad the sinuses swell up.)
This is a positive feedback loop, which means the activation of the pathway sends a signal to then increase activity even more, resulting in massive lung damage/remodeling/fibrosis crippling oxygen transport.
Bupleurum Falcatum ethanol extract inhibits STAT3 by 75%
Tetrahydrocurcuminoids inhibit TLR-4
This is, of course, not a preventative for infection but to mitigate damage if infected. This is also whole virus. Unknown if the Vax stimulated spike proteins do the same.
https://www.nature.com/articles/s41418-020-00633-7