Effectiveness of a 2-dose varicella vaccination program in Changzhou, China, during the transitional period (2017-2022): a registry-based case-cohort study.

Background: The benefits of improving coverage and timeliness of varicella vaccination need to be quantified in countries where varicella vaccine (VarV) has not yet been included in national immunization programs. This longitudinal study analyzed the vaccine effectiveness (VE) of the varicella vaccination program implemented in Changzhou City during the transitional period (2017-2022).

Methods: Using the Immunization Information System and National Notifiable Infectious Disease Surveillance System registry data, this retrospective case-cohort study assessed the VEs of varicella vaccination for Changzhou children born from 2016 to 2021.