Abstract
Objectives: The first large nosocomial cluster of coronavirus disease 2019 (COVID-19) in Singapore in April 2021 led to partial closure of a major acute care hospital. This study examined factors associated with infection among patients, staff and visitors; investigated the possible role of aerosol-based transmission; evaluated the effectiveness of BNT162.b2 and mRNA1273 vaccines; and described the successful containment of the cluster.
Methods: Close contacts of patients with COVID-19 and the affected ward were identified and underwent surveillance for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Patient, staff and visitor cohorts were constructed and factors associated with infection were evaluated. Phylogenetic analysis of patient samples was performed. Ward air exhaust filters were tested for SARS-CoV-2.
Results: In total, there were 47 cases, comprising 29 patients, nine staff, six visitors and three household contacts. All infections were of the Delta variant. Ventilation studies showed turbulent air flow and swabs from air exhaust filters were positive for SARS-CoV-2. Vaccine breakthrough infections were seen in both patients and staff. Among patients, vaccination was associated with a 79% lower odds of infection with COVID-19 (adjusted odds ratio 0.21, 95% confidence interval 0.05-0.95).
Conclusions: This cluster occurred despite enhancement of infection control measures that the hospital had undertaken at the onset of the COVID-19 pandemic. It was brought under control rapidly through case isolation, extensive contact tracing and quarantine measures, and led to enhanced use of hospital personal protective equipment, introduction of routine rostered testing of inpatients and staff, and changes in hospital infrastructure to improve ventilation within general wards.
Keywords: COVID-19; COVID-19 vaccines; Infection control; Outbreak; Phylogeny.
【저자키워드】 COVID-19, infection control, COVID-19 vaccines, outbreak, Phylogeny, 【초록키워드】 coronavirus disease, SARS-CoV-2, infection control, Personal protective equipment, Coronavirus disease 2019, vaccination, quarantine, COVID-19 pandemic, hospital, nosocomial, Infection, Ventilation, Contact tracing, severe acute respiratory syndrome coronavirus-2, severe acute respiratory syndrome Coronavirus, delta variant, Severe acute respiratory syndrome, Cohort, COVID-19 vaccines, Phylogenetic analysis, Measures, Surveillance, mRNA1273, Phylogeny, swabs, Patient, Effectiveness, Cluster, Breakthrough infection, Swab, Singapore, Care, patients, Coronavirus-2, household contacts, Analysis, vaccine breakthrough infections, Contact, Case isolation, with infection, quarantine measures, Inpatients, Inpatient, acute respiratory syndrome, Factor, adjusted odds ratio, acute respiratory syndrome coronavirus, 95% confidence interval, acute respiratory syndrome coronavirus-2, ward, measure, positive, enhancement, IMPROVE, tested, described, affected, occurred, examined, investigated, evaluated, nine, was performed, changes in, odds of infection, patients with COVID-19, with COVID-19, 【제목키워드】 hospital, nosocomial, Care,