Objective: To grasp the distribution characteristics and incidence trend of varicella in Shaanxi Province, so as to provide a reference for scientific and accurate prevention and control strategies. Methods: Data of 161 377 varicella cases in Shaanxi Province from 2016 to 2023 were collected and described from Surveillance Report Management System, a subsystem of National Disease Control and Prevention Information Systems of Chinese Center for Disease Control and Prevention. FlexScan 3.1.2 software was used to determine irregular spatial clustering, and spatial clustering area was detected for each year. Results: The incidence of varicella in Shaanxi Province showed a seasonal bimodal distribution with peaks from April to July (36.68%) and from October to next January (48.07%). The cases were mainly concentrated in the 3-12 years old group (60.50%), and there was a trend of high incidence age shift within the 0-19 age group from 2021. Most of the cases were students (62.40%) and preschool children ( 17.78 %). The outbreaks mainly occurred in primary schools (76.47%). The regional distribution was mainly concentrated in some areas of southern Shaanxi and Guanzhong. Through spatial analysis, the primary clusters were primarily concentrated in Ankang and Hanzhong cities in southern Shaanxi from 2016 to 2023, and the secondary clusters were mainly found in some areas of Guanzhong (Xi an, Baoji and Weinan cities). Conclusions Prevention and control of varicella should be focused on students and kindergartens aged 3-12 years in southern and Guanzhong areas of Shaanxi Province. Continuous varicella surveillance and vaccination measures should be carried out, and the two dose vaccination strategy and intensive vaccination of key groups should be actively promoted.

Objective To evaluate the effectiveness of vaccination on the onset of varicella and clinical symptoms of varicella based on the survey data of varicella outbreaks in schools.Methods Six schools with chickenpox outbreaks in Shaanxi Province were selected as the sites,and students in the classes or dormitories where the cases were located were chosen as the research subjects.A 1∶2 matching case control was used to conduct a questionnaire survey to analyze the relationship between the history of varicella vaccine immunization and the incidence of chickenpox so as to evaluate the effectiveness of varicella vaccine.Results The total prevalence of the six varicella outbreaks involved in this study was 1.39％.The proportion of chickenpox vaccinations was 44.53％,of which 15.78％ were vaccinations with two doses.The overall effectiveness of varicella vaccine was 63.52％ (95％ CI:40.690％-77.560％),and the effectiveness of one and two doses was 58.72％ and 72.90％,respectively.The effectiveness of varicella vaccine against moderate to high fever and moderate to severe rash was 82.77％ and 76.27％,respectively.The risk of chickenpox in people with vaccination intervals of 6 to 8 years and ≥ 9 years was 13.05 times and 3.93 times higher than that of those vaccinated before the age of 3 years,respectively.Conclusion Varicella vaccine has a good effectiveness on high-exposure people,and the effectiveness of two doses is better than that of one dose.Varicella vaccination can lessen the clinical symptoms of chickenpox.It is recommended to further strengthen the publicities of varicella vaccination and increase the number of children to complete two doses of varicella vaccination before entering nurseries,so as to actively and effectively control varicella outbreaks.

Objective To evaluate the effectiveness of vaccination on the onset of varicella and clinical symptoms of varicella based on the survey data of varicella outbreaks in schools.Methods Six schools with chickenpox outbreaks in Shaanxi Province were selected as the sites,and students in the classes or dormitories where the cases were located were chosen as the research subjects.A 1∶2 matching case control was used to conduct a questionnaire survey to analyze the relationship between the history of varicella vaccine immunization and the incidence of chickenpox so as to evaluate the effectiveness of varicella vaccine.Results The total prevalence of the six varicella outbreaks involved in this study was 1.39％.The proportion of chickenpox vaccinations was 44.53％,of which 15.78％ were vaccinations with two doses.The overall effectiveness of varicella vaccine was 63.52％ (95％ CI:40.690％-77.560％),and the effectiveness of one and two doses was 58.72％ and 72.90％,respectively.The effectiveness of varicella vaccine against moderate to high fever and moderate to severe rash was 82.77％ and 76.27％,respectively.The risk of chickenpox in people with vaccination intervals of 6 to 8 years and ≥ 9 years was 13.05 times and 3.93 times higher than that of those vaccinated before the age of 3 years,respectively.Conclusion Varicella vaccine has a good effectiveness on high-exposure people,and the effectiveness of two doses is better than that of one dose.Varicella vaccination can lessen the clinical symptoms of chickenpox.It is recommended to further strengthen the publicities of varicella vaccination and increase the number of children to complete two doses of varicella vaccination before entering nurseries,so as to actively and effectively control varicella outbreaks.