Strong antibody response correlates w/ more SEVERE clinical disease while strong T-cell response linkd w/ LESS severe disease. CD8 T-cells => signature of successful protective immunity. Note: CD8 T cells have the HIGHEST levels of vit. D receptor comprd w/other major immunecells Even vaccine developers admit this: sciencedirect.com/science/articl…
But they forget that T-cells need vitamin D: blogs.scientificamerican.com/observations/a…

So why are some people unable to mount a good protective T-cell response? The key to this question might be a 10-year-old Danish study led by Carsten Geisler, head of the Department of International Health, Immunology and Microbiology at Uni of Copenhagen. Geisler noted that: "When a T cell is exposed to a foreign pathogen, it extends a signalling device or 'antenna' known as a vitamin D receptor, with which it searches for vitamin D," and if there is an inadequate vitamin D level, "they won't even begin to mobilize." In other words, adequate vit. D

@c19d3k2 T- cells! 'The ability of complement to induce the expression of both VDR and the Vitamin D activating enzyme by T cells via CD46 binding is probably indicative of an autocrine or paracrine loop, which means that T cells activate VDR and respond to it.' news-medical.net/news/20200722/… @c19d3k2 'Prior experimental studies have shown that vitamin D regulates CD4+ T-cell responses by promoting T helper 2 (Th2) cells and suppressing T helper 1 (Th1) cells, thereby limiting Th1-mediated inflammatory responses and tissue damage while enhancing Th2-med. anti-inflam.responses'

Although serological and culture evidence of influenza infection has been documented in the summer, it seldom causes community outbreaks in summer.
cambridge.org/core/services/… If vitamin D is Hope-Simpson’s ‘seasonal stimulus’, then countries with low 25(OH)D levels+ marked wintertime troughs shd have higher excess wintertime mortality than countries with high 25(OH)D levels and little seasonal variation. Norway has highest 25(OH)D levels in Europe...