Protecting Preterm Infants From Respiratory Tract Infections and Wheeze by Using Bacterial Lysates.

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.