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Pang H.,Changning District of Shanghai Center for Disease Control and Prevention | Wang C.,Changning District of Shanghai Center for Disease Control and Prevention | Jiang Y.,Changning District of Shanghai Center for Disease Control and Prevention | Shi W.,Changning District of Shanghai Center for Disease Control and Prevention
Chinese Journal of Biologicals | Year: 2015

Objective To analyze the incidence of breakthrough varicella (BV) and the effectiveness of various doses and kinds of varicella vaccine. Methods The duration of outbreak in a primary school in Shanghai was from October 2011 to January 2012. Medical record of cases as well as vaccination status and history of varicella of all the students in the school were collected, based on which vaccine effectiveness (VE) and incidence were calculated. Results A total of 29 cases were observed in 444 children included in the analysis, indicating an incidence of 6.5%. The varicella vaccination coverage was 90.8%. The attack rate of vaccinated children was lower than those unvaccinated (X2 = 8.222, P < 0.05). Overall VE was 68.0% [95% confidence interval (CI): 55.2% - 80.9%]. The incidence rate of BV of children immunized with one dose of vaccine was 6.7%, while the VE was 60.8% (95% CI: 45.1% ∼ 76.6%). However, the incidence rate of BV and VE of children immunized with two doses of vaccine were 0 and 100% respectively. The incidence rate of BV of children immunized with two doses of vaccine was significantly lower than that with one dose (X2 = 1.701, P > 0.05). Conclusion High vaccination coverage with a single (lose of varicella vaccine is insufficient to prevent the outbreak in schools. However, two doses of varicella vaccine may be successful to decrease the BV. A second dose of varicella vaccine in children is recommended before entering primary school.

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