Varicella outbreaks were mainly reported in developed regions with high vaccine coverage but not in undeveloped areas. It is still not clear whether the published data of varicella epidemiology could reflect the reality in China or not.

Researchers included 657 subjects from the People’s Hospital of Chongqing Youyang County. ELISA determined Anti-VZV IgG antibodies. The anti-VZV IgG levels were categorized as positive when values were ≥100 mIU/mL. Our results showed that the rates of anti-VZV IgG seropositivity and geometric mean titers were significantly influenced by age. The seropositivity declined dramatically from 84.5% in subjects ≤3 m of age to 7.9% in subjects of >3 m-1 y. Then, the positivity rate increased slowly as age to 26.7% in >1-<3 y, and 34.5% in 3-<7 years. A steady rise in positivity was observed in subjects aged 7-<18 y. After then, the positivity began to increase robustly. A total of 87.8% of adults aged 18-<40 y had acquired VZV-specific immunity. Researchers found the highest positivity rate in the 40-<60 y  and ≥60 y group.

The study concluded that most>3 m-<7 y age were susceptible to VZV. The proportion of subjects with natural infection-induced immunity increased with age.