ABSTRACT
Objective@#To understand the vaccination of varicella attenuated live vaccine (VarV) among students in collective institutions, to provide a basis for analying the protective effect of vaccination.@*Methods@#All collective institutions with chickenpox epidemic and post exposure vaccination in Jing an District from 2017 to 2019 were investigated. All students( n =6 473) in the affected class were included. Vaccination status and the incidence information of disease were collected to analyze vaccine effectiveness (VE).@*Results@#The proportion of study subjects without an immunization history decreased year by year, and 7.5% in 2017, 7.2 % in 2018, and 4.9% in 2019. The proportion with a history of one dose prior to exposure in cases was 90.0%, it was lower than 93.5% in the non cases ( χ 2=6.53, P <0.05). The proportion with one dose as post exposure prophylaxis in cases was 8.3%, it was much lower than 44.1% in the non cases ( χ 2=179.06, P <0.01). The proportion with one dose as post exposure prophylaxis in secondary cases was 28.6%, much lower than 44.1% in the non cases ( χ 2=9.44, P <0.01).Unvaccinated ones and the second dose as post exposure prophylaxis ones in cases had the highest rate of varicella development (11.0%), a history of one dose prior to exposure and one dose as post exposure prophylaxis in cases had the lowest varicella rate (1.0%).There was a clear protective effect within two years after one dose of VarV inoculation, VE was 63.1%(95% CI =11.0%-84.7%).@*Conclusion@#The vaccine effectiveness of one dose VarV was limited. Post exposure prophylaxis as early as possible was highly effective in decreasing secondary attack rate.