Risk factors for outbreaks of COVID-19 in care homes following hospital discharge: a national cohort analysis

Abstract

AbstractBackgroundAdult residential and nursing care homes are settings in which older and often vulnerable people live in close proximity. This population experiences a higher proportion of respiratory and gastrointestinal illnesses than the general population and has been shown to have a high morbidity and mortality in relation to COVID-19.MethodsWe examined 3,115 hospital discharges to 1,068 Welsh adult care homes and the subsequent outbreaks of COVID-19 occurring over an 18 week period between 22 February and 27 June 2020. A Cox proportional hazards regression model was used to assess the impact of time-dependent exposure to hospital discharge on the incidence of the first known outbreak, over a window of 7-21 days after discharge, and adjusted for care home characteristics, including size, type of provision and health board.ResultsA total of 330 homes experienced an outbreak of COVID-19, and 544 homes received a discharge from hospital over the study period. The exposure to discharge from hospital was not associated with a significant increase in the risk of a new outbreak (hazard ratio 1·15, 95% CI 0·89, 1·47, p = 0·29) after adjusting for care home characteristics. Care home size was by far the most significant predictor. Hazard ratios (95% CI) in comparison to homes of <10 residents were: 3·40 (1·99, 5·80) for 10-24 residents; 8·25 (4·93, 13·81) for 25-49 residents; and 17·35 (9·65, 31·19) for homes of 50+ residents. When stratified for care home size, the outbreak rates were similar for periods when homes were exposed to a hospital discharge, in comparison to periods when homes were unexposed.ConclusionOur analyses showed that large homes were at considerably greater risk of outbreaks throughout the epidemic, and after adjusting for care home size, a discharge from hospital was not associated with a significant increase in risk.Research in contextWhat is already known on this subjectCare home populations experience more respiratory outbreaks than the general population1 and older people have been more severely affected by COVID-19, with a case fatality proportion of 2·3% overall but 8% in those aged 70-79 and 14·8% in those aged over 802Evidence and modelling suggested that up to half of all COVID-19 fatalities could come from the care home population3 and that testing prior to hospital discharge was not always available or undertaken9Type and use of PPE6 and the number of staff employed can have an impact on care home outbreaks of COVID-196,7What this study addsOur analysis found no effect of hospital discharges on care home outbreaks once care home size had been adjusted for. In line with previous studies, larger care homes were much more likely to experience an outbreak