The purpose of this study is to assess the efficacy and safety of J022X ST for prevention of Recurrent Upper-Respiratory Tract Infections (RURTI) compared to placebo in children of younger age who develop infectious diseases more frequently than other children of this age in general.

Key Inclusion Criteria:

Patients with all the following criteria will be eligible for inclusion in Year 1:

• Children, male or female
• Aged 3 to 4 years
• Children known for recurrent URTIs in the past year (based on medical recording or reported history)
• Children at risk for URTI in the physician's opinion (e.g. absence of breastfeeding, hospitalization in the previous year, tonsillectomy or adenoidectomy, parental smoking, daycare institution or nursery school, early schooling, prematurity, low weight at birth, malnutrition, failure to thrive).

Patients with all the following criteria will be eligible for randomisation in Year 2:

• Children, male or female
• Aged 4 to 5 years
• Suffering from RURTI, i.e. at least 6 URTI episodes medically confirmed, with a maximum of 18, during the Year 1 of the study.

Key Exclusion Criteria:

Presence of diseases (Chronic suppurative otitis media, acute broncho-pulmonary infection, Immune deficiency or disorders, surgery of respiratory tract, cystic fibrosis…) or treatments (chronic use of corticosteroids, bronchodilators, ...) that may impact the safety, the interpretation of the results and/or the participation of the subject in the study