[Analysis of the clinical characteristics of COVID-19 reinfection cases].

Objective: To explore the epidemiological and clinical characteristics of COVID-19 reinfection cases. Methods: The published COVID-19 reinfection cases were reviewed and the relevant data were extracted, including the baseline characteristics of patients, the results of antibody tests, and the whole-genome sequencing results of the viral strains. Results: We reviewed 29 reinfection cases in 20 reports from 14 countries. The age of re-infected patients ranged from 21 to 90 years (median 53 years), and there was no significant difference in gender distribution. Among the 29 patients, 11 were health care workers, 6 received immunosuppressive drugs (including glucocorticoids), 17 presented more severe symptoms than their primary infections and 5 (all aged over 80 years) died. The interval of the two infections was usually less than 60 days when the patients were infected by the same viral strain,while the interval was much longer (median 78.5 days) when the patients were infected by different viral strains. Nine patients had negative antibody test results or low antibody titers when the reinfections were confirmed, and 5 of them had negative antibody test results even during the initial infection. Conclusions: Virus-specific antibodies had a protective effect against COVID-19 reinfection for the majority of the population, however, this effect may decrease over time. Occupational exposure, low levels of antibodies, or an inability to produce antibodies may be the main risk factors for reinfection. Advanced age was a major risk factor for a poor prognosis. Effective personal prevention and social distancing were still essential for the prevention of reinfection.