More promising results were reached using daily or weekly administration of vitamin D for longer periods of time. A 2010 Japanese study found that daily administration of vitamin D (1,200 IU/die) to schoolchildren during winter months reduced the incidence of influenza A infections [156]. In 2012, Camargo and colleagues [159] investigated the administration of vitamin D-fortified milk during winter months in Mongolian children, and reported significantly lower RTI episodes during the study period. A Chinese 2019 prospective study analyzed a cohort of infants recording whether they received vitamin D daily supplementation (400–600 UI/die) up to 6 months of age, and reported the median time of the first RTI episode, which ended up being 60 days in infants without supplementation and longer than 6 months in infants with supplementation [168].