ABSTRACT
OBJECTIVE: To understand the epidemiological characteristics of confirmed cases of COVID-19 in Xi 'an, Shaanxi Province during cluster outbreak and explore the prevention and control strategies for the epidemic caused by the Delta SARS-CoV-2 variant. METHODS: The confirmed cases of COVID-19 who were treated in Xi'an People's Hospital, a designated hospital, were enrolled in the study, the data of the patients such as baseline data, diagnostic types and initial symptoms were retrospectively reviewed. RESULTS: Among 703 confirmed cases of COVID-19, the gender ratio of male to female was 1.16:1, the age ranged between 10 months and 94 years old, with the median age 33 years old;the patients with mild symptoms(58.46%) and the patients with common symptoms(39.12%) were dominant. 70.13% of the patients were vaccinated with 2 doses of COVID-19 vaccine, 13.51% have not been vaccinated. In terms of the initial symptoms of COVID-19, the patients with cough accounted for 42.96%, the patients with pharyngeal symptoms accounted for 29.87%, and the patients with fever accounted for 25.60%. Totally 129 patients did not have obvious symptoms during the initial stage. There was significant difference in the influence of age and vaccination on severity of disease(P<0.05). The patients aged no less than 60 years old were the high-risk population for the severe(57.14%) and critically severe(66.67%) symptoms;the morbidity rates of severe symptoms(50.00%) and critically severe symptoms(66.67%) were high among the patients without vaccination. CONCLUSION: The local cluster outbreak caused by Delta SARS-CoV-2 variant in Xi 'an, Shaanxi province are characterized by strong transmission power and fast transmission. It is necessary to focus on the prevention and control among the populations of infants and old people, enhance the epidemiological surgery, precisely trace and isolate close contacts, identify and take interventions to illness condition in early stage. In daily prevention and control, fever, as a typical symptom, should be monitored, and it is necessary to boost the comprehensiveness and sensitivity of symptom monitoring. Universal vaccination remains one of the effective measures for protection of vulnerable populations.