Asthma-related symptoms, such as wheezing, are highly prevalent among preschool children. Asthma is a complex disease and originates from genetic susceptibility combined with different environmental exposures. Early life is a specific critical period for development of later-life asthma.1 Population studies have identified various fetal and early-childhood risk factors for asthma, including early-life respiratory tract infections.1 Early-life respiratory tract infections have not only short-term consequences, but seem also to affect the development of both the respiratory and immune systems,…