Objective To analyze the epidemiologic features of imported COVID-19 cases in Nanjing from January 2020 to July 2022,and provide reference basis for epidemic prevention and control.Methods Information on infected persons was obtained from the Information System of Chinese Disease Control and Prevention and epidemiology investigation reports,and relevant data were analyzed in a descriptive epidemiological manner.Results From 1 January 2020 to 31 July 2022,a total of 360 imported COVID-19 cases were reported in Nanjing,of which 63.89％(230/360)were asymptomatic.The sex ratio of male-to-female was 2.40∶1,and the median age of onset was predominantly 20 to＜40 years.Fifty-eight point zero six percent(209/360)COVID-19 cases were from Italy,Russia,Singapore,and Nigeria.The time interval of median(M)(P25,P75)from the entry to the first positive nucleic acid sample was 2(0,6)days,and 33.06％(119/360)COVID-19 cases had the first positive nucleic acid detection on the day of the entry.In terms of the vaccination with the SARS-CoV-2 vaccine,48.61％(175/360)of the imported COVID-19 cases had received the COVID-19 vaccine,and there was a statistically significant difference(x2=9.593,P=0.044)in the vaccination status among different age groups.There was no statistically significant difference in Ct value between the vaccinated group and the unvaccinated group[ORF1ab gene(Bioperfectus reagent:Z=-0.223,P=0.824;DAAN reagent:Z=-0.150,P=0.880);N gene(Bioperfectus reagent:Z=-1.024,P=0.306;DAAN reagent:Z=-0.580,P=0.562)].Conclusion The imported COVID-19 cases in Nanjing are mainly asymptomatic,and most of them are young and middle-aged men.Lukou Airport as the site with the highest number of reported imported COVID-19 cases in Nanjing,and the prevention of imported cases is still the key to epidemic prevention and control.
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