https://www.sciencedirect.com/science/article/abs/pii/S0960076017300031 https://www.sciencedirect.com/science/article/abs/pii/S09600... Vitamin D levels in sum

https://www.sciencedirect.com/science/article/abs/pii/S0960076017300031 https://www.sciencedirect.com/science/article/abs/pii/S09600... Vitamin D levels in summer months are associated with 25% lower mortality rates for all causes. Vitamin D almost certainly influences the immune system to fight off Covid in the same way it does the seasonal flu and other pneumonia. There's hundreds more studies on Vitamin D. Read up when you get a chance. Hell even if it was a 5% reduction we're talking an abundant vitamin that costs pennies to manufacture.