Impact of a 2-dose voluntary vaccination strategy on varicella epidemiology in Beijing, 2011–2017

Abstract

BackgroundOne-dose voluntary varicella vaccination for children was introduced in Beijing since 1998. In Oct 2012, a second dose varicella vaccine (VarV) was recommended to further decrease varicella disease and the outbreaks. We describe the impact of the 2-dose voluntary vaccination strategy on varicella epidemiology in Beijing, China. MethodsVaricella incidence rates and outbreak characteristics in 2011–2017 was examined using surveillance data. Varicella vaccination coverage among children born in 2007–2012 was estimated through Beijing children immunization registry system. Vaccine effectiveness (VE) for VarV2 was estimated by screening method. ResultsOverall varicella incidence decreased by 37.8% from 103.2 per 100,000 population in 2011 to 64.2 per 100,000 population in 2017. Incidence declines in children aged <15 years with most significantly decrease by 82.3% in children aged 5–9 years, while no significant change happened in adolescent and adults. A total of 251 outbreaks with 3239 outbreak-related cases were reported in 2011–2017, the number of outbreaks decreased significantly by 50.7% from 69 in 2011 to 34 in 2017. The VarV1 coverage ranged from 85.4% to 92.6% among children 4 year of age and the VarV2 coverage ranged from 40.1% to 72.9% among children 6 year of age in the 2007–2012 birth cohort. Overall VE estimates against all varicella disease was 94.4% (95% CI: 89.9–98.9%) for VarV2. ConclusionsModerate VarV2 coverage has been achieved in Beijing resulting in remarkable declining of the incidence in children. Varicella outbreaks has not been eliminated suggested that measures such as including a 2-dose varicella vaccination in routine immunization program should be taken in the future.