International Journal of Medicine and Data

Objective To elucidate the epidemiological characteristics of repeated infections with novel coronavirus (COVID-19) in Harbin, the recovery process, and the related factors influencing the clinical severity of repeated infections, providing a scientific basis for formulating epidemic prevention and control policies in the new stage. Methods Case data of secondary infections with SARS-CoV-2 in Harbin from May 2023 to October 2024 were analyzed to explore their epidemiological characteristics. A total of 200 cases of secondary COVID-19 infections and asymptomatic infected individuals were randomly selected for case investigation. The χ² test and logistic regression model were used to analyze the influencing factors of clinical manifestations in repeated infections. Results From May 2023 to October 2024, the proportion of secondary COVID-19 infections in Harbin was 16.86%. The rate of repeated infections was higher in females than in males (χ²=61.781, P<0.001). The lowest rate of repeated infections was observed in individuals under 3 years old (0.52%), while the highest rate was in the elderly population aged 60-79 years (35.34%). Compared with the first infection, the recovery time for secondary infections was significantly shortened (χ²=91.864, P<0.001). Asymptomatic infected individuals with a history of previous illness and male patients with mild symptoms exhibited lower clinical severity during repeated infections. Conclusion In this study, the overall proportion of secondary COVID-19 infections in Harbin was relatively low. The clinical severity of secondary infections was reduced, and the recovery period was shortened. In future prevention and control efforts, attention must be paid to repeated infections in elderly female populations.

COVID-19; Repeated infection; Epidemiological characteristics; Vaccination