All adverse events during hospitalization will be recorded on a four-point scale (0-3) and their possible relation to study drug will be assessed on a three-point scale (no, possible, likely, Appendix 4). Parents will be asked to record all adverse events on a two-week home symptom diary (Appendix 5). Investigator shall report all clinically meaningful adverse events in a timely correct manner to the national authorities (Lääkelaitos) according to national law, and to Leiras / Drug Safety Officer Johanna Kause. In case of premature termination of the trial, due to safety concerns, the investigator shall write a safety summary report and immediately forward this to Leiras and the national authorities. In case of an emergency, sealed envelope containing the randomization code will be available in the patient chart in the Turku University Hospital and can be easily opened.