[Niacin increases cellular free & decreases ester cholesterol] https://www.jlr.org/article/S0022-2275(20)39224-5/fulltext

HDL-C-mediated cholesterol efflux & selective cholesterol transport become dysfunctional in chronic metabolic diseases such as obesity or atherosclerosis, consistent with the increased mortality observed in elderly patients & patients w/obesity or diabetes

Niacin increases serum total and HMW adiponectin concentrations and decreases lipolysis within minutes following GPR109A receptor activation. Because adiponectin concentrations are generally low and adipose tissue lipolytic activity high in obese individuals with the metabolic syndrome, niacin may be an ideal pharmacological approach to reduce CVD in this population.

Protection against/risk of #SARS_CoV_2 infection (& similarly for progression of #COVID19 severity as shown in another report) is (independently) associated with only HDL-C (/ApoA-I) and not LDL-C, ApoB, triglycerides, or anything else.

a 10 mg/dl increase in serum HDL-cholesterol or apolipoprotein A1 levels was associated with ∼10% reduced risk of SARS-CoV-2 infection, after adjustment for age, sex, obesity, hypertension, type 2 diabetes, and coronary artery disease. https://www.jlr.org/article/S0022-2275(21)00043-2/fulltext

a 0.2 mmol/L increase in HDL-C was associated with a corresponding 9% reduction in risk for COVID hospitalization. A very similar pattern of association was apparent when COVID-19 mortality was the outcome of interest.