[Research progress on the mechanisms and assessment indicators of abnormal vaccine immune responses in sepsis survivors].

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Although advances in early recognition and standardized management have improved in-hospital survival, sepsis survivors remain at increased risk of reinfection, readmission, functional decline, and long-term mortality after discharge. Growing evidence indicates that post-sepsis immune abnormalities do not represent a simple linear transition from inflammatory activation to immunosuppression. Rather, they reflect a persistent and heterogeneous state of immune reprogramming characterized by the coexistence of ongoing inflammation and immunosuppression, with concurrent impairment of both innate and adaptive immunity. The major features of this state include reduced antigen-presenting capacity of myeloid cells, innate immune hyporesponsiveness, persistent lymphopenia with T-cell dysfunction, remodeling of humoral immunity and immune memory, and the coexistence of persistent inflammation and immunosuppression. These alterations may disrupt multiple steps required for effective vaccine responses, including antigen presentation, T-cell help, germinal center formation, functional antibody generation, and maintenance of immune memory, thereby leading to reduced vaccine immunogenicity, insufficient protective efficacy, or shortened durability of protection. Direct clinical evidence regarding vaccination in sepsis survivors remains limited. However, available studies suggest that absolute lymphocyte count (ALC), monocyte human leukocyte antigen-DR (mHLA-DR) expression, and programmed cell death protein 1/programmed death ligand 1 (PD-1/PD-L1) related phenotypes may help identify individuals at high risk of poor vaccine response and inform post-vaccination reassessment and long-term follow-up. This narrative review summarizes the immune status of sepsis survivors, the potential mechanisms underlying abnormal vaccine immune responses in different immune states, and the current approaches to predicting and evaluating vaccine responsiveness, with the aim of informing precision immunoprophylaxis and future prospective study design in this special population.