Epidemiological and Clinical Characteristics of COVID-19 Outbreak in a Mental Hospital in Wenzhou, China, December 2022–January 2023

BACKGROUND: Coronavirus disease (COVID-19) mainly caused by the Omicron virus strain currently is still prevalent worldwide, and many medical institutions have experienced COVID-19 outbreaks in the past three years. OBJECTIVE: This article reported COVID-19 outbreak among health care workers in a mental hospital to clarify the epidemiological and clinical characteristics of COVID-19 outbreak in a medical institution, to assess the susceptible factors related to COVID-19 among these personnel and to evaluate the effect of COVID-19 vaccine on the medical workers. METHODS: A uniform questionnaire was used to investigate all employees, including age, gender, department, time of onset, clinical symptoms, vaccination status. At the same, the results of laboratory testing, chest computed tomography (CT) and/or X-ray examination were collected. RESULTS: Among 1047 hospital employees, 842 cases were diagnosed as COVID-19, with a total attack rate of 80.42%. The attack rate of doctors, nurses, medical technicians, and administrators (83.50–90.67%) was higher than that of logistics departments (56.81%). Out of the 842 patients, 9 were hospitalized; 833 were non-hospitalized patients who belong to mild or moderate cases. No deaths were reported. The full vaccination rate and booster rate of COVID-19 vaccine were 78.26% and 80.87%, respectively. There was no significant correlation between the attack rate and COVID-19 vaccine (χ(2) = 3.41 P > 0.05). CONCLUSION: This is an outbreak of COVID-19 with a high attack rate among employees in a mental hospital. The attack rate of medical personnel is higher than that of logistics personnel, which may be related to opportunities and duration of contact with infected individuals. COVID-19 vaccine has no significant protective effect on patients with mild or moderate symptoms 13 months after the full vaccination. It is suggested that they should be timely boostered with COVID-19 vaccine to maintain their immunity to the disease.