P-114. Nasal-Spray Bacillus Spore Probiotics Prevent Respiratory Infections in Preschoolers: A Community RCT

Abstract Background Respiratory tract infections (RTIs) are a leading cause of pediatric morbidity and excessive medication use, contributing to antimicrobial resistance. Current preventive strategies remain limited in long-term effectiveness.Figure 1:Incidence of viral (A) and bacterial (B) infections in the Control group (white bars) and Navax group (black bars) across all participants at days 0, 14, and 28. Methods Here, we evaluated the efficacy of nasal-spraying Bacillus spore probiotics in reducing RTI incidence and medication use among preschool children. In a randomized, double-blind, controlled trial, preschool children aged 2–5 in Hanoi, Vietnam received daily nasal sprays for 28 days during the winter-spring transition. The intervention (Navax) group received LiveSpo NAVAX (>1 billion CFU/mL of B. subtilis ANA4 and B. clausii ANA39), while the Control group received physiological saline. Clinical symptoms, medication usage, viral/bacterial infections, and nasal microbiota were assessed at days 0, 14, and 28. Results Compared to control, the Navax group showed significant reductions in RTI symptoms, including runny nose (−42.4%), tonsillitis (−83.3%), tonsillitis-adenoiditis (−61.7% at day 14; −36.2% at day 28), hoarseness (−66.7%), and sore throat (−73.9%). Medication use (antibiotics, anti-inflammatories, cough suppressants, expectorants, and antihistamines) decreased by 27–75% (p < 0.05). Viral infection incidence dropped by 69.2%, with a 92.3% reduction in rhinovirus cases, and risk of acquiring new viral infections was reduced by 5–6-fold. Bacterial co-infections also decreased: M. catarrhalis (−50%), H. influenzae (−67.6%), and S. pneumoniae (−40.5%). Nasal microbiota analysis revealed increased abundance of beneficial genera (Brevibacillus, Bacillus, Flavobacterium) and decreased pathogenic taxa (Moraxella, Dolosigranulum, Haemophilus). Conclusion This study provides the first clinical evidence that daily nasal-spraying Bacillus spores offer a safe, microbiome-friendly, and broad-spectrum strategy to reduce respiratory infections, lower medication use, and prevent both viral and bacterial transmission in young children. Disclosures Anh Hoa Nguyen, PhD. in Life Sciences, LiveSpo Pharma Ltd. Company: Board Member Anh Thi Van Nguyen, PhD, LiveSpo Pharma Ltd. Company: Advisor/Consultant