ObjectiveTo determine the serum antibody level and risk factors in the adolescent population in a county in Zhejiang Province， following the immunization with inactivated COVID-19 vaccine， and to construct a prediction model for antibody concentration. MethodsWe conducted the study in a county in Zhejiang Province， employing a stratified cluster random sampling strategy in school children who had received the inactivated COVID-19 vaccine. Data on gender， age， type of vaccine， and time of vaccination was collected. Serum samples were also collected to test for anti-S and N IgG antibody against the SARS-CoV-2 by using chemiluminescent immunoassay （CLIA）. Risk factors were determined to construct a prediction model for antibody concentration. ResultsThe IgG antibody concentration was significantly higher in girls， those who received two doses， and those who had simply received the KX vaccine . It decreased with age and time interval between the sampling and last vaccination. The prediction model constructed by random forest regression in the study had a better model fit and predictive ability than that by the multivariable linear stepwise regression. ConclusionGender， age， vaccination dose， type of vaccine， and time of vaccination are associated with vaccination effectiveness of inactivated COVID-19 vaccines in adolescents. Prediction model could predict the antibody level in the vaccinated population， which can provide a new tool for better evaluation of vaccination effectiveness against emerging infectious diseases in future.

ObjectiveTo understand the usage of antibiotics in outpatients in a county of Zhejiang Province from 2015 to 2020， so as to provide a basis for further standardizing the clinical application of antibiotics in this region. MethodsOutpatient records and prescription records of 146 public medical institutions from 2015 to 2020 were extracted from the electronic medical record data sharing platform system of medical institutions in a county of Zhejiang Province. The utilization rates and the number of types of antibiotics used in outpatient patients were described. According to the drug anatomy， therapeutic and chemical classification system （ATC）， clinical application classification and dosage form， the use status of different types of antibiotics was observed. The annual percentage change （APC） was used to analyze the time trend of antibiotic use. Among the antibiotic prescriptions in each year， the proportions of prescriptions aimed for different use reasons and patients were compared to analyze the changes in the structures of antibiotic prescriptions. ResultsDuring 2015‒2020， a total of 2 861 438 prescriptions were issued in146 primary public medical institutions in this county， including 314 642 prescriptions for antibiotics， and the overall utilization rate of antibiotics was 11%. The utilization rate of antibiotics showed a decreased trend across the years （from 14.23% in 2015 to 7.59% in 2020，APC=-11.51%， 95%CI=-0.01%‒-21.7%， t=-12.05， P<0.001） and an obvious seasonal variation character （higher in winter and spring， lower in summer and autumn）. Cefoxitin sodium for injection was the most used antibiotic in 2015， and cefuroxime was the most used antibiotic from 2015 to 2020， respectively. The utilization rates of cephalosporins （APC=-11.06%， 95%CI=0‒-20.89%， t=-22.233， P<0.001）， quinolones （APC=-9.74%， 95%CI=0‒-18.53%， t=-7.652， P=0.002）， macrolides （APC=-17.52%， 95%CI=0‒-17.52%， t=-3.626， P=0.022） and lincoamides （APC=-49.01%， 95%CI=0‒-74%， t=-3.35， P=0.029） showed a decreasing trend across the years. There were differences in the distribution of drug use reasons （χ²=9 458.427， P<0.001）， as well as the age （χ²=5 421.709， P<0.001） and sex （χ²=245.322， P<0.001） of patients. During the observation period， 50.69% of antibiotic prescriptions were used to treat respiratory diseases， with the highest proportion of 57.67% in 2015 and the lowest proportion of 34.93% in 2020. 58.37% of patients were aged 50‒70 years， with a decreasing proportion of patients under 50 years （17.83% in 2015， 6.64% in 2020） and an increasing proportion of patients over 70 years （24.1% in 2015， 38.41% in 2020）. ConclusionThe utilization rate of antibiotics used in outpatients from primary public medical institutions in a county of Zhejiang Province shows a decreasing trend across the years， but higher than that of secondary and above hospitals in China， and also higher than that of primary medical institutions in economically-developed areas. The management and monitoring of the clinical use of antibiotics in the county should be actively strengthened.

Objective To analyze the prevalence status,influencing factors,and differences among different school age groups of myopia in children and adolescents in Ningxia Hui Autonomous Region.Methods From September to De-cember 2019,inYinchuan,Wuzhong,Shizuishan,Guyuan and Zhongwei of Ningxia,8 primary schools,6 junior high schools,6 senior high schools and 4 universities were randomly selected by stratified cluster random sampling.Five classes were se-lected from each grade of primary school,and four classes were selected from each grade of junior high school to university.All students in the selected classes were included in the study.A total of 14 211 students were selected for questionnaire sur-vey,physical examination and visual acuity measurement.The influencing factors of myopia in children of different grades were analyzed using the least absolute shrinkage and selection operator(LASSO)and logistic regression,and the model with the smallest Bayesian information criterion(BIC)was selected as the optimal model.Results The detection rate of myopia in children and adolescents in Ningxia Hui Autonomous Region was 70.3％.The detection rate of myopia in girls was higher than that in boys,and that in cities was higher than that in towns,with statistically significant differences(both P＜0.001).Compared with primary school students,the detection rate of myopia in junior high school students,senior high school students and college students gradually increased,and that in the college students was the highest,with statistically signifi-cant differences among different grades(all P＜0.001).The LASSO-logistic regression analysis of the influencing factors of myopia showed that urban and rural areas,gender,age,whether or not to wear glasses at present,the number of daily break exercises,whether or not to actively participate in physical activities,and whether or not to maintain regular exercises in the past 6 months were the influencing factors of myopia in primary school students(all P＜0.05).Gender and whether or not to wear glasses at present were the influencing factors of myopia in junior high school students and senior high school students(all P＜0.05).Whether or not to wear glasses at present was the influencing factor of myopia in college students(P＜0.05).Conclusion The detection rate of myopia in children and adolescents in Ningxia Hui Autonomous Region is high,and there are significant differences in the influencing factors of myopia among different age groups of children and adolescents.Wear-ing glasses is a protective factor to control myopia.Targeted health education on vision should be provided based on the aca-demic stage of children and adolescents to enhance their awareness of health care and improve their visual health.

ObjectiveTo investigate the specific anti-SARS-CoV-2 antibody in adults and above after initial vaccination with inactivated COVID-19 vaccine， and determine the influencing factors. MethodsIn this study， residents aged 18 and above who had completed two doses of inactivated COVID-19 vaccine in Deqing County， Huzhou City， Zhejiang Province were included. Information such as gender， age， type of vaccine and vaccination time were collected， and serum specimens were sampled. Anti-SARS-CoV-2 receptor binding domain （RBD） antibody was quantitatively examined by enzyma-linked immunosorbent assay （ELISA） and influencing factors were determined. ResultsThe median concentration of anti-SARS-CoV-2 IgG antibody in the residents vaccinated with an inactivated booster vaccine was higher than that in those vaccinated with only two doses of COVID-19 vaccine or single dose （P<0.05）. The median concentration of IgG antibody in males was 9.73 （4.01‒23.70） RU‧mL^-1， lower than 17.76 （7.07‒49.23） RU‧mL^-1 in females （P<0.05）. The median concentration in the residents vaccinated with BBIBP-CorV （Sinopharm） was 6.53 （0.97‒13.69） RU‧mL^-1， which was lower than that in those vaccinated with CoronaVac （Sinovac） that was 17.29 （8.54‒43.73） RU‧mL^-1 （P<0.05）. The median concentration in those with BBIBP-CorV was also lower than 12 （5.45‒40.06） RU‧mL^-1 in those with heterologous booster vaccine （P<0.05）. The median concentration was 9.73 （3.83‒23.63） RU‧mL^-1 in the residents with an interval of more than 6 months from the second dose， which was lower than 14.66 （6.36‒35.98） RU‧mL^-1 in those with an interval of 3‒6 months （P<0.05）. Moreover， immune effect was better in females （χ²=16.464， P<0.05）， 18‒45 years（χ²=7.158， P<0.05）， and those vaccinated with CornaVac （χ²=49.637， P<0.05）， while decreased in those with an interval of more than 6 months from the second dose （χ²=8.447， P<0.05）. ConclusionGender， age， and type of vaccine may affect the effect of immunization. The COVID-19 vaccination shows an acceptable immunogenicity in adults； however， it declines in 6 months after vaccination. It warrants strengthening the booster vaccination to maintain the immune response.

Objective: To understand secular trend of blood pressure among Han ethnic students aged 7-18 years in Ningxia from 2000 to 2014，and to provide preliminary evidence for hypertension prevention and control. Methods: Data of blood pressure, height, weight of Han students aged 7-18 years in Ningxia were collected in the National Students Physical Fitness and Health Survey during 2000-2014 years were analyzed by using SPSS 21.0. Results: From 2000 to 2014, the systolic pressure of the Han students in Ningxia showed a decreasing-increasing trend(F=357.44, P<0.05), with an average decrease of 3.37 mm Hg; diastolic pressure showed a decreasing-increasing trend(F=172.95, P<0.05), with an average decrease of 4.18 mm Hg; pulse pressure showed a decreasing-increasing trend(F=311.86, P<0.05), with an average decrease of 1.98 mm Hg. The body mass index of the Han nationality students in Ningxia was on the rise(F=128.15, P<0.05). The detection rates of high blood pressure, high systolic blood pressure and high diastolic blood pressure increased by 1.0, 0.4 and 0.9 percentage. Conclusion Blood pressure in Ningxia Han students aged 7-18 years increases gradually in recent years, which warrants further attention. Health education and health promotion is needed to prevent the occurrence of hypertension.

Objective: To analyze the trend of overweight and obesity among Han students aged 7-18 years in Ningxia from 2000 to 2014, and to provide scientific basis for child and adolescent obesity prevention and control in Ningxia. Methods: Based on data of the height and weight of Han students aged 7-18 in the four waves of national student physical surveys in Ningxia from 2000 to 2014, SPSS 21.0 was used for trend analysis. Results: From 2000 to 2014, the overweight and obesity rate of Han students in Ningxia from 7 to 18 years old showed an upward trend. Compared with the year of 2000, the total overweight rate increased by 2.06 times in 2014 and the obesity rate increased by 4.40 times. The overweight and obesity rate of boys was higher than that of girls in 2005 and 2014, and the difference was statistically significant(χ2=4.91, 6.20, P<0.05). The overweight and obesity rates of urban students were higher than those of rural students in 2005 and 2010(χ2=9.63, 5.97, P<0.05). The correlation analysis between the overweight and obesity rate of Ningxia students and socioeconomic indicators showed that the overweight and obesity of Ningxia students from 2000 to 2014 was closely related to the level of Ningxia socioeconomic development, especially the obesity detection rate of rural students was related to Ningxia’s GDP and The correlation between GDP, per capita disposable income, per capita consumption expenditure, and urbanization rate is stronger(r=0.98, 0.98, 0.99, 1.00, 0.93, P<0.05). Conclusion Socioeconomic of Ningxia is rapidly increasing, and the overweight and obesity rate of Han students aged 7 to 18 is also increasing. It is suggested that society, schools and parents should pay great attention to this phenomenon, build community-wide efforts to prevent childhood obesity, and prevent chronic diseases caused by overweight and obesity occurrence risk.

Objective: To understand the vitamin D nutritional status and associated factors of children and adolescents aged 6-18 in Yinchuan, so as to provide theoretical basis for improving the vitamin D malnutrition status of children and adolescents. Methods: Using stratified cluster sampling method, 1 615 children and adolescents from 36 classes in 2 primary schools, junior high schools and high schools were randomly selected from Yinchuan, Ningxia. Venous blood sampling,physical examinations and questionnaires were conducted. Results: The vitamin D deficiency rate and appropriate rate for students were 66.9% and 33.1%, respectively. There was a statistically significant difference in vitamin D deficiency among different age groups(χ2=25.65, P<0.05). The 6-year-old group had the highest(79.2%), followed by the 13-year-old group (76.6%), and the 12-year-old group (75.3%). The results of binary Logistic regression showed that the factors influencing the vitamin D nutritional status of children and adolescents included age(OR=0.95), daily outdoor exercise time(OR=0.49), exclusive breastfeeding (OR=0.63) and mother’s education(OR=0.73, 0.43). The decision tree QUEST and Logistic regression combination model results show that the key factors affecting vitamin D nutrition status include daily outdoor exercise time, age, mother’s education, BMI, and interaction between outdoor exercise time and age, interaction between outdoor exercise time and mother’s education, interaction between age and mother’s education, interaction between exclusive breastfeeding and BMI. Conclusion The detection rate of vitamin D deficiency in children and adolescents aged 6-18 in Yinchuan is high, factors associated with vitamin D nutritional status includes daily outdoor exercise time, age, mother’s education, BMI, and interaction between outdoor exercise time and age, interaction between outdoor exercise time and mother’s education, interaction between age and mother’s education, interaction between exclusive breastfeeding and BMI.

Objective: To investigate the visual acuity of primary and middle school students in Ningxia by using decision tree model and logistic regression, and to provide evidence for the prevention and control of visual acuity. Methods: Using stratified cluster sampling method, 3 257 children aged 7-18 years were randomly selected from Yinchuan and Wuzhong in Ningxia. Visual acuity test and questionnaire survey were conducted. The C 5.0 algorithm in Clementine12.0 and Logistic regression were used to analyze the factors associated with visual acuity. Results: The overall rate of low vision of the middle school of Ningxia was 62.6%, with girls (68.1%) higher than that of boys(56.8%)(P<0.01). There was a significant difference in the prevalence of low vision among different educational stages(P<0.01), with high school students had the highest detection rate(82.2%). Results of decision tree C 5.0 algorithm showed that educational stage, gender, time to do homework after school and frequency of moderate intensity exercise per week associated with poor eyesight of primary and secondary school students. Logistic regression results showed that girls, the distance between the eyes and the computer display screen <66 cm(OR=1.24, 95%CI=1.00-1.52), and the distance between the eyes and the textbook when reading was less than one foot (OR=2.05, 95%CI=1.23-3.40) were positively associated with poor vision. Low grade students and homework time <2 hours after school (OR=0.76, 95%CI=0.62-0.92) were negatively associated with lower risk of poor vision. Conclusion Educational stage, gender and time of homework after school are associated with the visual acuity of primary and secondary school students in Ningxia. It is suggested that prevention of myopia should start from the low-grade students, reducing after-school work for primary and secondary school students, and increasing outdoor activities. All the girls should be encouraged to engage in more outdoor activities, to prevent the occurrence and development of myopia.

Objective: This paper analyzes the changing trends of lower limb strength and flexibility in colleges in Ningxia for 14 years, and provides a reference for government and school to jointly guide college students to improve their lower limb strength and flexibility. Methods: Data of physical health of 19 to 22 years old college students in Ningxia were collected from 2000-2014. Mean value, standard deviation and index compliance were used to describe the development trend of lower limb strength and flexibility indexes. Results: From 2000 to 2014, the variation trend of lower limb strength of boys and girls in ningxia university was basically the same, and they all decreased first, then increased and then decreased(P<0.05). The variation trend of flexibility of boys and girls was basically the same, rising first and then falling (P<0.05). The mean values of standing long jump and sitting forward bend of boys and girls were higher in rural area than in urban area (P<0.05). There was no age group difference in the mean of standing long jump of girls in 2014, and no age group difference in the mean of standing long jump of boys and girls in other years (P<0.05). Conclusion The lower limb strength and flexibility of boys and girls in Ningxia from 2000 to 2014 showed a declining trend, and effective intervention measures should be taken in time.

Objective: To understand the current situation of infrastructure construction and sanitation practice of school canteens in China and to provide a reference for improving food safety in school canteen and sanitation management level. Methods: Stratified sampling method was adopted to select the surveyed schools. Information regarding school canteen infrastructure and sanitation practice was collected through questionnaires. Chi-square test was used to compare the difference in passing rate on the survey indices among different school types. Results: In environmental sanitation, 91.0% of the school canteen was rated as good and in personal hygiene, 92.8% of the employees were rated as good. The overall health level of urban schools was better than that of township schools, and non-boarding schools was better than that of boarding schools, with statistically significant differences(P<0.01). 67.1% of school canteens provided with independent food outlets while 98.7% of school canteens without independent food stores. The qualified rate of washing facilities in the dining area was 94.7%, and the qualified rate of distance between the canteen and the pollution source was 92.5%. Nearly all the employees held canteen catering service license (99.0%) and the health qualification certificate (99.5%). Most of the school canteens (98.7%) established the safety rules and regulations, including the food retention sample system. Nearly 61.5% schools initiated the principal meal program. Conclusion Sanitation management in the canteens of primary and secondary schools in China is generally satisfactory, with some canteens still fail to meet the standard requirements. More supervision from schools and relevant government departments (market supervision, health and education departments) is needed to provide students with a clean and heathy campus canteen.