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.