Mk montelukast, PBO placebo, P primary, S secondary, USMA unscheduled medical attendance, WE wheezing episode, CS corticosteroid, EVS episodic viral wheeze, MTW multiple-trigger wheeze, ALOX5 arachidonate 5-lipoxygenase, BID budesonide inhalation suspension, EFD episode-free day, QOL quality of life, AEE asthma exacerbation episodes, ICS inhaled corticosteroid