Prevention With Ismigen of RTIs in Kids

Inclusion Criteria: 1. Children of both genders aged from 3 to 12 years. 2. Written informed consent obtained from the parents/legally authorized representatives 3. Written assent obtained from the subject from 7 years 4. Subject presenting with a susceptibility to respiratory tract infections according to the investigator 5. No respiratory tract infection within 15 days before the randomization visit 6. All girls of childbearing potential have a negative pregnancy urine testing at randomization visit and are informed and their parents as well of the requirement for contraception during the study. 7. A cooperative attitude and ability to correct use of PMBL® tablet. Exclusion Criteria: 1. Subject treated with bacterial lysates within the previous 6 months prior to V1 or ongoing treatment. 2. Body temperature ≥ 37.5°C at the randomization visit. 3. Pregnant/Lactating female or with sexual activity without hormonal contraception, intrauterine device or barrier methods. 4. Primary or secondary immunodeficiency, cystic fibrosis, bronchiectasis, alpha-1 antitrypsin deficiency, malignancy, endocrinological diseases or other chronic respiratory diseases, except asthma and allergic rhinitis. 5. Known sensitivity to the components of study medication. 6. Any major surgery within the last 3 months prior to study enrolment or planned to occur within the duration of study. 7. Treatment with the following medications: 1. Injection or oral administration of steroids within 4 weeks prior to study enrolment. 2. Previous and/or concomitant immunosuppressants, immunostimulants, allergen-immunotherapy or gamma globulins within 6 months prior to study enrolment. 8. Inability to understand or comply with study procedures or with study treatment intake. 9. Subject participating in another interventional clinical study at the time of screening visit.