Abstract：Objective To analyze the epidemiological characteristics of coronavirus disease 2019 (COVID-19) local infections in Zhejiang Province during the period between March and May, 2022, so as to provide the evidence for COVID-19 control. Methods The individual investigation data and field epidemiological investigation data of local COVID-19 cases in Zhejiang Province from March to May 2022 were extracted from the National Diseases Prevention and Control Information System of China. The temporal, spatial and population distribution, identification and booster vaccination of local COVID-19 cases were analyzed using a descriptive epidemiological method. Factors affecting the severity of clinical symptoms were identified among local COVID-19 cases using a multivariable logistic regression model. Results A total of 289 local COVID-19 epidemics occurred in Zhejiang Province from March to May 2022, and all infections were caused by the Omicron variant. A total of 1 598 local COVID-19 infections were reported, including 672 confirmed cases (42.05%) and 926 asymptomatic cases (57.95%), and the 672 confirmed case included 614 mild cases (91.37%), 58 normal cases (8.63%), while no severe, critically ill or dead cases were reported. The mean duration of COVID-zero community, mean duration of COVID-19 epidemics and mean length to COVID-19 peak calculated according to 7 epidemics with 50 and more cases were (6.14±1.07), (13.43±4.39), (3.00±1.63) d, respectively. COVID-19 infection was predominantly detected in centralized quarantine sites (1 105 cases, 69.15%), and 843 cases completed booster immunization of COVID-19 vaccines (52.75%). Multivariable logistic regression analysis showed that age (with ages of 60 years and older as the reference, age of 6 to 17 years, OR=0.111, 95%CI: 0.024-0.508; age of 18 to 44 years, OR=0.341, 95%CI: 0.163-0.713) and booster COVID-19 vaccination (OR=0.219, 95%CI: 0.117-0.410) were protective factors for developing more severe clinical symptoms following COVID-19 infections. Conclusions All local COVID-19 infections were caused by Omicron variant in Zhejiang Province during the period between March and May 2022, and all cases had mild clinical symptoms. Preschool children, middle-aged and elderly residents and individuals that did not complete booster COVID-19 vaccination may had relatively more severe clinical symptoms following COVID-19 infections.
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