CRP and major depressive disorder: Further, we have shown that circulating levels of inflammatory mediators (ie. C-reactive protein [CRP]) are inversely correlated with responses to the varicella-zoster virus vaccine [29], while others have shown them to be related to the risk of adverse outcomes in older adults, such as depression [30], cardiovascular disease [31], frailty [32], and all-cause mortality [31, 33].