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

ABSTRACT 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 < .001). The positive rates of antibodies increased with increasing doses of vaccination (χ2 = 56.252, P < .001). For the protective effect of one-dose and two-dose, it was found that the protection rates of one-dose were 72.98% and 100.00%, respectively. The varicella vaccine is an effective method to prevent varicella disease, which can increase serum seroprevalence levels and block the transmission of varicella disease.