It's both sad and hilarious that the CDC is still recommending frequently disinfecting your doorknobs. As if that's going to make a difference in the pandemic.
Meanwhile we have very strong evidence from multiple controlled clinical studies that hypovitaminosis D is a critical risk factor.
in california at least, we did exactly the wrong thing in this regard: we closed down all gyms for over a year, and even shut down outdoor recreational facilities, to the point that outdoor basketball rims, soccer goals, and tennis nets were removed, outdoor gym equipment chained, and outdoor trails were closed. it was beyond idiotic.
Is washing hands and sanitizing touch points (like doorknobs) ever not effective at preventing disease? Hand Washing seems to be one of the few things doctors have never wavered on since the beginning of germ theory.
It's not effective in cases where the disease is neutralized by the environment before you would wash your hands anyways. A lot of diseases can't survive outside the body for long; I think this is more true of viruses than bacteria, but I could be wrong.
E.g. HIV doesn't last long outside the body. By the time blood dries, almost all of the HIV is neutralized.
I think the research has said COVID is similar, and can really only live on a surface for minutes.
Hand washing is great for preventing disease generally. It's less effective against some diseases, but it also has virtually no downsides, so it's still a sane thing to do.
I don't think I'd classify any of those studies as "very strong evidence". Lots of studies in many different environments(some uncontrollable) measuring different things at different dosages. It doesn't exactly result in finding any particular conclusion, certainly not "Vitamin D supplementation effectively prevents, reduces harm or cures COVID".
I didn't say you said that, but looking at study summaries that state things like "high-dose cholecalciferol supplementation led to SARS-CoV-2 RNA negative status" is why I mentioned "cure".
At the bottom of the page you linked, you'll find a link for "People at Increased Risk"(also found via "Specific Groups of People" link on sidebar), you'll then click on "Medical Conditions"[1], which mentions a list of medical conditions that increase risk, including obesity. Obesity section links you to the CDC's "Healthy Weight, Nutrition, and Physical Activity" page[2], which discusses exactly what you mention.
Meanwhile we have very strong evidence from multiple controlled clinical studies that hypovitaminosis D is a critical risk factor.
https://vitamin-d-covid.shotwell.ca/