Impact of Immunisation Strategies and Public Health and Social Measures on Varicella Incidence: An Analysis of Surveillance Data from Quzhou City, 2006–2022

Background. To assess the impact of different immunisation strategies and public health and social measures (PHSMs) on the incidence of varicella in Quzhou. Methods. We collected data on varicella cases reported in Quzhou City from 2006 to 2022, constructed an interrupted time-series (ITS) regression model, and evaluated changes in monthly varicella incidence during three periods: the single-dose varicella vaccine (VarV) immunisation strategy period, the two-dose VarV immunisation strategy period, and the PHSMs implementation period. Results. ITS analysis indicated that, during the single-dose VarV immunisation strategy period, the incidence of varicella exhibited a significant upward trend (p < 0.001). Following the introduction of the two-dose VarV immunisation strategy, the monthly incidence decreased immediately by .848 per 100,000 population (p = 0.057), representing a marginally significant change. Immediately following the implementation of PHSMs, the monthly incidence of varicella declined by 2.960 cases per 100,000 population ( p  = 0.034), a statistically significant reduction. In the longer term, the monthly incidence of varicella increased by 0.032 cases per 100,000 population following the introduction of the two-dose VarV immunisation strategy ( p  = 0.367), while a decline of 0.043 cases per 100,000 population was observed after the implementation of PHSMs( p  = 0.370), although neither change was statistically significant. Conclusions. This study suggests that the low coverage of the two-dose VarV vaccination in Quzhou has contributed to its limited effectiveness in curbing the long-term upward trend in varicella incidence. Furthermore, while the implementation of PHSMs can serve as a useful complementary strategy to help prevent varicella, their impact on the transmission dynamics of the disease appears relatively limited.