Seroprevalence rates in children aged 3-6 years after implementing a two-dose varicella vaccination: A observational study

The study evaluates the outcomes of including varicella vaccines (VarV) in the local expanded programme on immunization (EPI) on the seropositivity rates and corresponding protective effects for children aged 3–6 years in Suzhou. The study is observational. Varicella prevalence in children was assessed based on data from the China Information System for Disease Control and Prevention (CISDCP) and the Jiangsu Province Vaccination Integrated Service Management Information System (JPVISMIS). Seropositivity was determined using the enzyme-linked immunosorbent assay (ELISA). A total of 2,873 children aged 3–6 years were enrolled in this study. The seropositivity rates were 95.31% and 86.89% for children with and without the strategy, respectively. The difference in seropositivity rate in children using the different strategies was statistically significant (Trend χ2 = 0.397, P = .255). It is therefore suggested that Suzhou had a high rate of occult infection before the inclusion of varicella vaccine in the EPI. The difference in seroprevalence rate between children with no history of varicella vaccination and those with a history of varicella vaccination was statistically different (χ2 = 51.362, P