Our primary endpoint is the occurrence of new wheezing episode within 2 months after discharge. According to our previous data on rhinovirus induced first or second episode of wheezing in children aged less than 3 years, the prevalence of relapses within 2 months after discharge in prednisolone group is 22% and in placebo group 56%. To maintain an alpha error of 0.05 and a beta error of 0.20, the required size of the sample is 29 children for each treatment group for the 2-month follow-up. When assessing the risk for the development of asthma at age 6 years, we expect 60% in the rhinovirus group and 18% in the RSV group to develop asthma by that age. We expect approximately 10-20% of the children to discontinue the study within 6 years. Thus, 35 children are needed in each group for the follow-up until school-age.