Varicella epidemiology, susceptibility and cost burden in Chongqing China: implications for prevention and control...

To characterize the epidemiological profile, population seroprotection levels, and economic impact of varicella in Chongqing, and to provide evidence to optimize immunization strategies to reduce incidence and economic burden.

The epidemiological trends of varicella in Chongqing were ascertained from routine surveillance data (2011-2024). Population sero-epidemiology was evaluated using a randomized cross-sectional serosurvey (n = 960, 2024), and economic burden was estimated from 14,779 outpatient and 298 inpatient cases (2019-2022). Statistical analyses (descriptive statistics, Chi-squared test, Kruskal-Wallis test, and Wilcoxon rank-sum test) were conducted to quantify incidence trends, factors associated with antibody levels, and heterogeneity in economic burden.

A total of 301,714 cases were reported during 2011-2024, with 53.56% in children < 15 years. Incidence exhibited an inverted U-shaped trend. The overall crude varicella IgG seroprevalence was 78.33% (geometric mean concentration, GMC: 351.3 mIU/mL). Notably, children (< 15 years) showed a significant seroprotection gap (seroprevalence: 70.54%; GMC: 240 mIU/mL), which aligned with their disproportionately high incidence. Two-dose vaccination was associated with significantly higher seropositivity (83.50% vs. 66.07%) and GMC (343.7 vs. 189.1 mIU/mL) than one dose (p < 0.01). Adults aged > 50 years exhibited the highest GMC (744.7 mIU/mL) and seropositivity (96.15%), aligning with the lowest incidence recorded in 2024. The pediatric inpatients (< 15 years) had a higher burden ($1375.74 vs. $1012.70, p < 0.01) than individuals over 15 years.

Varicella incidence remains high and children show suboptimal seroprotection against varicella in Chongqing. The disease imposes a substantial financial burden, particularly among pediatric inpatients. It is recommended to expand two-dose varicella vaccine immunization coverage to reduce both incidence and disease burden.