Background
Adult 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.
Methods
We examined the number of hospital discharges to all Welsh adult care homes and the subsequent outbreaks of COVID-19 occurring over an 18 week period 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).
Results
A total of 1068 care homes were monitored; 330 homes experienced an outbreak of COVID-19, and 511 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, 1.49, p = 0.28), after adjusting for care home size, which was by far the most significant predictor. Hazard ratios (95% CI) in comparison to homes of <10 residents were: 3.4 (2.0, 5.8) for 10-24 residents; 8.3 (5.0, 13.8) for 25-49 residents; and 17.3 (9.6, 31.1) for homes of 50+ residents. When stratified for care home size, the outbreak rates were very similar for periods when homes were exposed to a hospital discharge, in comparison to periods when homes were unexposed.
Conclusion
Our 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.
Keywords: COVID-19, care homes, hospital discharge, outbreak, time dependent Cox regression