ObjectiveTo understand the nutritional status of vitamin D in some children aged 0-14 in Mianyang during the past 3 years and the changes of vitamin D nutritional status under home protection during the coronavirus disease 2019 (COVID-19) epidemic, so as to provide a theoretical basis for the monitoring and reasonable supplementation of vitamin D in children in this area after the epidemic.MethodsThe clinical data of children aged 0-14 who underwent physical examination in the Children’s Health Department of Mianyang Central Hospital from January to April 2018, from January to April 2019 and from January to April 2020 were analyzed retrospectively. High performance liquid chromatography tandem mass spectrometry was used to detect vitamin D, including vitamin D2, vitamin D3 and 25-hydroxyvitamin D [25(OH)D] in children’s serum. The differences in vitamin D components and 25(OH)D between different genders, different age groups, and different years were analyzed.ResultsA total of 12 348 children were included. The average vitamin D2 was (4.89±6.02) ng/mL, the average vitamin D3 was (22.91±9.29) ng/mL, the average 25(OH)D was (27.81±10.53) ng/mL, and 9 434 cases had sufficient 25(OH)D. The differences in vitamin D2, vitamin D3, 25(OH)D and 25(OH)D nutritional status in 2018, vitamin D2 and 25(OH)D in 2019, and vitamin D2 in 2020 between different genders were not statistically significant (P>0.05). There were statistically significant differences in vitamin D3 and 25(OH)D nutritional status in 2019, vitamin D3, 25(OH)D and 25(OH)D nutritional status in 2020 between different genders (P<0.05). From 2018 to 2020, vitamin D2 was the highest in infant group (P<0.05), while vitamin D3, 25(OH)D and 25(OH)D nutritional status were the highest in children group (P<0.05); vitamin D2 (χ2=143.106, P<0.001) showed an overall downward trend, vitamin D3 (F=400.178, P<0.001) and 25(OH)D (F=447.384, P<0.001) showed an overall upward trend; 25(OH)D nutritional status (χ2=103.566, P<0.001) was the highest in 2019.ConclusionsThe overall vitamin D nutritional status of children in Mianyang area is acceptable. Under the home protection, the average level of children’s serum 25(OH)D has little change, while the nutritional status of 25(OH)D has decreased significantly. After the outbreak of COVID-19, more attention should be paid to the monitoring and supplementation of vitamin D in school-age female children.