Inclusion Criteria:  Gestational age at delivery between 30+0 and 35+6 weeks Postnatal age at least 6 weeks at randomization & postmenstrual age at least 37 weeks Written informed consent by both parents or formal caregivers  Exclusion Criteria:  Underlying other severe respiratory disease such as broncho-pulmonary dysplasia (unexpected in this group); hemodynamic significant cardiac disease; immunodefi-ciency; severe failure to thrive; birth asphyxia with predicted poor neurological out-come; syndrome or serious congenital disorder. Lower RTI before randomization Dysmaturity and/or weight < 2.5 kg at age of randomization. Maternal TNF-alpha inhibitors or other immunosuppression during pregnancy and/or breastfeeding Parents unable to speak and read Dutch/English language Known allergic hypersensitivity to the active ingredients/substance or to any of the excipients.