Abstract:Objective：To analyze the clinical features of secondary booster immunization with the second dose of COVID-19 vaccine in medical staff. Methods：Medical staff who received the second dose of booster injection in a certaintertiary hospital from December 23 to 25，2022 were selected as the investigation subjects. Data such as age，sex，occupation，time of the second booster dose，infection with COVID-19，and related symptoms were collected.Independent sample t test and Pearson correlation analysis were used to complete data analysis. Results：A total of 227 subjects were included in this study. The mean age were 38.1 ± 11.9 years，170（74.9%）women，130 clinical departments（57.3%）. The average interval from the second booster dose was 21.0 ± 10.1 days，the shortest was 1 day and the longest was 57 days. There were 159 cases（70.0%）with COVID positive，There were 175 cases（77.1%）with related symptoms，among which the incidence of cough，sore throat，headache and catarrhal symptoms were 83.4%，69.1%，60.0% and 59.4%，respectively. The time of the second dose of booster injection was different among the medical staff who were infected with COVID-19 and had accompanying symptoms（such as cough，sore throat and headache）（P < 0.05）. Conclusions：Early routine vaccination can help prevent the onset of COVID-19 infection and ease the onset and duration of symptoms. In the future，public awareness of public health prevention should be further improved，and high-risk groups should be actively immunized as soon as possible to reduce the risk of infection.