[Mariner]

In most of North America there is not enough sunlight to produce adequate D3 between mid Sep and mid Mar. Even on sunny days.

What sun you get is filtered through more atmosphere and of a shorter duration.

And D3 is essential to the body’s ability to fight off infection along with C.

[amorphous]

And D3 is essential to the body’s ability to fight off infection along with C.

Exactly, and I believe I've read that the vast majority of Americans are D deficient. I take D3/K2, daily, and still get quite a bit of outdoor exposure on most days.

But in the context of what causes the well know drop in the flu during warmer months, I feel confident the increase in natural vitamin D in the populace during the summer is a key factor as well.

[firebrand]

This is why northern peoples are taller and less bumpy, some say: it exposes more skin area to the sun per ounce of body weight. Also, white skin helps.

[amorphous]

The U.S. Government Is Preparing For An 18 Month Pandemic And "Critical Shortages"

https://www.zerohedge.com/health/us-government-preparing-18-month-pandemic-and-critical-shortages

Link to plan:

https://int.nyt.com/data/documenthelper/6819-covid-19-response-plan/d367f758bec47cad361f/optimized/full.pdf#page=1