Objective To investigate the effects of Mycobacterium vaccae vaccine on immunological function and clinical character in elderly patients with stable chronic obstructive pulmonary disease (COPD). MethodsA total of 100 elderly patients with stable COPD were randomly divided into immunotherapy group (group A, n= 50) and non-immunotherapy group (group B, n= 50), and normal control group (group C, n = 50). The levels of peripheral blood T-lymphocyte subsets (CD3+ , CD4+, CD8+ , CD4+/CD8+ ratio), natural killer cells (NK cells), immunoglobulins (IgG, IgA, IgM) and cytokines (IL-6, IL-8, TNF-a) were measured respectively before and after therapy. Group A and B were followed up for 1 year, then the times of acute outbreak and hospitalization of patients in the two groups were also compared. Results The levels of CD4 + ,CD4+/CD8+ ratio and NK cells in group A, B were significantly lower before therapy (P＜0. 05～0. 01＝, and the levels of IL-6, IL -8, TNF-a and IgA were significantly higher than in group C (P＜0. 01＝. After treatment with Mycobacterium vaccae vaccine in group A, the levels of CD4+ , CD4+/CD8+ ratio and NK cells were significantly higher (P＜0. 05-0. 01＝ and IL-6, IL-8, TNF-a and IgA were significantly lower than before treatment (all P＜0. 01＝. These levels showed no significant changes in group B after treatment (P＞0. 05). After 1-year follow-up, the times of acute outbreak and hospitalization on patients were statistically lower in group A than in group B (P＜ 0. 01 ).ConclusionsMycobacterium vaccae vaccine can improve cellular immunity function and reduce the times of acute outbreak and hospitalization in patients with stable COPD, so it has a higher clinical application value.