Human parainfluenza viruses (hPIVs) are a major cause of severe respiratory disease in (very) young children and the immunocompromised. hPIVs are the second main cause of hospitalization due to acute respiratory tract infection in children under five (respiratory syncytial virus ranks first). There are no clinically approved vaccines or antivirals available against hPIVs to prevent or treat these infections. Our group recently isolated antibodies that can neutralize hPIVs. In this project we aim to generate data to support the clinical potential of these antibodies.