Polypeptide derived from the hypothalamo-pituitary axis-system, as a pre-pro-hormone along with vasopressin and neurophysin II. Employed for assessing the individual stress level in comparison to cortisol. Prognostic accuracy of copeptin in acute illness like sepsis, pneumonia, lower respiratory tract infections and stroke has been analyzed successfully. Here, AVP is linked to Recurrent lower respiratory tract infections.