Upper Respiratory Tract Infection (URTI)

The goal of this clinical trial is to learn if Immune X can help prevent common cold events in healthy adults who have a history of upper respiratory tract infections. The main questions it aims to answer are: * Does Immune X reduce the proportion of participants who experience at least one clinically confirmed common cold event during the study period? * Does Immune X affect the number, duration, and severity of common cold events? Researchers will compare Immune X to a placebo (a look-alike capsule containing inactive ingredients) to see if Immune X helps prevent common cold events. Participants will: * Take Immune X or placebo daily for 16 weeks during the winter season. * Attend study visits at the beginning and end of the study and complete questionnaires and symptom assessments throughout the study. * Record cold symptoms, medications, and other study information using a smartphone application. * Provide blood and stool samples during the study.

This randomized, double-blind, placebo-controlled pilot study will evaluate the effect of a probiotic supplement on upper respiratory tract infections (URTIs) in children aged 4-18 years with a history of recurrent URTIs. Participants will be randomized to receive either probiotic drops or placebo drops. The primary objective is to assess the effect of the probiotic on the frequency of URTI episodes during the study period. Secondary objectives include evaluation of respiratory symptoms, medication use, healthcare visits, school absenteeism, recovery of the administered probiotic, and safety.