Background Immunostimulating agents made from bacterial extracts represent a class of medications that contains antigens derived from several bacterial strains and their potential ability to prevent bacterial infections results from the stimulation of the nonspecific component of the immune system. The present study investigated the effect of the oral immunostimulant Broncho-Vaxom,which includes material from eight different species of bacteria that are frequently present in the lower respiratory tract,on the frequency and severity of acute exacerbation in patients with chronic bronchitis accompanied by chronic obstructive pulmonary disease (COPD). Methods Ninety patients with chronic bronchitis complicated with COPD were randomly divided into groups A and B. Forty-nine subjects in group A received oral capsules containing 7mg Broncho-Vaxom,while 41 patients in group B received similar placebo capsules. Both groups took one capsule daily for the first 10 days of each month for 3 consecutive months. The frequency of acute exacerbation,symptom scores,and lung function were recorded for the following one year period.Results There was a significant decrease in the incidence,duration,and severity of acute exacerbation,as well as a reduction in the course of antibiotics administered and in the dosage of bronchodilator and mucolytic agent in group A,as compared to group B ( P <0.05,respectively). Symptom scores for cough,sputum,dyspnea,as well as symptoms observed upon auscultation of the chest also improved significantly in group A as compared to group B ( P <0.05,respectively). The bacterial clearance rate in sputum cultures from patients who received no antibiotics for the first 3 months was also significantly higher in group A compared to group B ( P <0.01).Conclusions Orally administered Broncho-Vaxom is associated with a decrease in the incidence of acute exacerbation and a decrease in the need for antibiotics and symptomatic relief medications in patients with chronic bronchitis accompanied by COPD. Broncho-Vaxom is also associated with a decrease in symptom scores. Without causing any apparent adverse effects,this drug may also help to eradicate pathogenic bacteria in the airways. Background Immunostimulating agents made from bacterial extracts represent a class of medications that contains antigens derived from several bacterial strains and their potential ability to prevent bacterial infections results from the stimulation of the nonspecific component of the immune system. The present study investigated the effect of the oral immunostimulant Broncho-Vaxom, which includes material from eight different species of bacteria that are frequently present in the lower respiratory tract, on the frequency and severity of acute exacerbation in patients with chronic bronchitis accompanied by chronic obstructive pulmonary disease (COPD). Methods Ninety patients with chronic bronchitis complicated with COPD were randomly divided into groups A and B. Forty-nine subjects in group A received oral capsules containing 7 mg Broncho-Vaxom, while 41 patients in group B received similar placebo capsules. Both groups took one capsule daily for the first 10 days of each month for 3 consec The frequency of acute exacerbation, symptom scores, and lung function were recorded for the following one year period. Results There was a significant decrease in the incidence, duration, and severity of acute exacerbation, as well as a reduction in the course of antibiotics administered and in the dosage of bronchodilator and mucolytic agent in group A, as compared to group B (P <0.05, respectively). Symptom scores for cough, sputum, dyspnea, as well as seen as auscultation of the chest also improved significantly in group A as compared to group B (P <0.05, respectively). The bacterial clearance rate in sputum cultures from patients who received no antibiotics for the first 3 months was also significantly higher in group A compared to group B (P <0.01 ). CONCLUSION Orally administered Broncho-Vaxom is associated with a decrease in the incidence of acute exacerbation and a decrease in the need for antibiotics and symptomatic relief medications in patients with chronbronchitis accompanied by COPD. Broncho-Vaxom is also associated with a decrease in symptom scores. Without causing any apparent adverse effects, this drug may also help eradicate pathogenic bacteria in the airways.