Objective To explore the correlation between the severity of pulmonary infection and the vitamin D level in children.Methods A total of 124 pediatric patients treated at The First Affiliated Hospital to Xi′an Jiaotong University between February 2012 and November 2015 were included.All children

diagnosed as community-acquired pneumonia（CAP）

were divided into two groups

i.e.severe group（n=42）and mildto-moderate group（n=82）according to the severity of CAP.Meanwhile

another 90 healthy children undergoing health checkup at the same hospital were included as the control group.The vitamin D level was compared among the three groups

and the correlation between the severity of pulmonary infection and the vitamin D level was analyzed.Results The highest 25（OH）D3level was observed in the control group and the lowest in the severe group

with significant differences among the three groups（F=34.230

P<0.05）.The 25（OH）D3level was significantly lower in the severe group compared with the mild-to-moderate group（LSD-t=15.353

P<0.05）or the control group（LSD-t=22.721

P<0.05）;and that in the mild-to-moderate group was also significantly lower compared with the control group（LSD-t=9.581

P <0.05）.The Spearman′s correlation analysis showed that

the severity of pulmonary infection was negatively correlated with the 25（OH）D3level in children（r=-0.379

P<0.01

95%CI=-0.581to-0.124）.Conclusion The severity of pulmonary infection is closely correlated with the vitamin D level in children.