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

One-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.

Varicella 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.

Overall 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.

Moderate 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.