[Epidemiological characteristics of public health emergency events of varicella in China, 2006-2021]

Objective: To understand the epidemiological characteristics of public health emergency events (PHEE) of varicella in China from 2006 to 2021 and related response performances. Methods: The data of varicella PHEE in 31 provinces of China from 2006 to 2021 were collected through the Public Health Emergency Management Information System, Microsoft Excel 2019 software and SPSS 26.0 statistical software were used to conduct descriptive epidemiological, statistical analysis on the time, area, location distribution, scale and epidemic management. Results: A total of 11 443 PHEE involving 341 048 related cases were reported from 2006 to 2021, with an annual attack rate of 1.78%-3.80% and a total attack rate of 2.33% (341 048/14 624 042). The number of PHEE and related cases of varicella decreased from 1 107 (35 349) in 2007 to 262 (6 884) in 2012 (Z=-2.40, P<0.001), then increased year by year to 1 318 (42 649) in 2019 (Z=2.58, P<0.001), with a significant decline since 2020. The varicella PHEE in China presents the seasonal characteristics,the peak is from April to June and from October to December, respectively. The sub-peak of varicella PHEE in eastern China generally appears 1-2 months earlier than in central and western China. Varicella PHEE reports are mainly distributed in eastern China, the attack rate is relatively high in western China, school-reported varicella PHEE was 88.26% of the total reports (10 099/11 443). The epidemic scale of varrcella PHEE typically range from 10 to 29 cases per year among the given outbreaks. The M (Q1, Q3) of average number of cases, average duration, and average reporting interval of PHEE were 23 (16,35), 20 (14, 26) days, and 9 (5,19) days, respectively, and the reporting interval was positively correlated with the duration (r=0.854, P<0.001). Conclusions: The varicella PHEE in China from 2006 to 2021 has not been effectively controlled. Schools are the key places to prevent and control varicella PHEE. Improving the sensitivity of varicella PHEE monitoring, strengthening the timely disposal of varicella epidemic, and promoting varicella vaccination are effective measures to prevent and control varicella PHEE.