Primary prevention of acute respiratory tract infections in children using a bacterial immunostimulant:: A double-masked, placebo-controlled clinical trial

Background: Acute respiratory tract infections (ARTIs) are among the main causes of morbidity and mortality in children. The bacterial extract OM-85 BV has shown some protective effect for ARTIs in preschool children and a reduction in exacerbations of chronic bronchitis in adults. Objectives: This trial reports results of a double-masked, placebo-controlled, parallel-group clinical study that assessed the efficacy and tolerability of OM-85 BV in the prevention of ARTIs in school girls living in an orphanage. Methods: Two hundred girls (age range, 6 to 13 years) living in an orphanage entered the trial. Participants were randomly allocated to receive either OM-85 BV or placebo for 10 consecutive days a month for 3 consecutive months. Patients were followed up for 6 months, including the administration period. The trial began in September 1996 and finished in March 1997. Primary end points were the type and number of infections. Secondary end points included when an infection occurred, time to clinical cure, severity of infection, absenteeism from school due to an ARTI, number of antibiotics or other drugs prescribed, and duration of concomitant drug treatment. Results: During the trial, patients in the OM-85 BV group experienced 143 ARTIs (135 upper ARTIs and 8 otitis episodes) and patients in the placebo group experienced 299 ARTIs (273 upper ARTIs, 1 lower ARTI, and 25 otitis episodes). The median number of ARTIs was 1.0 (0.0, 3.0; 5th percentile, 95th percentile) in the OM-85 BV group compared with 3.0 (2.0, 4.0; 5th percentile, 95th percentile) in the placebo group. This difference was statistically significant (P < 0.001). Participants who received OM-85 BV also showed significantly better results (P < 0.001) than participants who received placebo in terms of median duration of illness, median number of missed school days due to an ARTI, median number of antibiotic and drug courses, and median duration of concomitant treatment. There were significant differences (P < 0.05) in severity of ARTIs during month 4 of the trial, with patients receiving OM-85 BV showing less severe ARTIs than patients receiving placebo and shorter mean time to clinical cure from the second month to the fourth month. No adverse events related to the trial medications were reported. Conclusions: OM-85 BV had a preventive effect on ARTIs in the school girls, with a reduction in the antibiotic requirements and the duration of ARTIs. Future studies are needed to further explore the role of OM-85 BV in the prevention of ARTIs.