Evidence summary: What research is there linking hospital discharges to Covid-19 outbreaks in long-term care facilities?

William Byrd, Maximilian Salcher-Konrad (Care Policy and Evaluation Centre, Department of Health Policy, London School of Economics and Political Science).

This evidence summary seeks to identify and summarise research that investigates links between hospital discharges and Covid-19 outbreaks in long-term care facilities (covering the period up to October 18, 2021).

Key findings:

  • All comprehensive studies on the association of hospital discharges and Covid-19 outbreaks in long-term care facilities we identified were from the United Kingdom.
  • Four nationwide or regional studies (two from England, one each from Scotland and Wales) investigated patterns of the introduction of Covid-19 into care homes, including through hospital discharges, and associated outbreaks.
  • Hospital discharges were also mentioned in some outbreak reports on the experience of individual long-term care facilities in the UK and other countries.
  • All the studies are subject to substantial uncertainty due to data limitations.


Studies reporting on hospital discharges and associated Covid-19 outbreaks in long-term care facilities in the UK were identified from an ongoing evidence mapping review as part of the Social Care COVID Recovery and Resilience Research project. Details of the methodology for this review, which documents the scientific literature on Covid-19 and long-term care more broadly, were published as a pre-print on LTCcovid.org (Byrd et al., 2021). Searches were updated up to 18/10/2021.

Brief summaries of the findings of these studies are provided below.

Studies identified:


Hamilton et al., 2021, describe a retrospective genomic analysis of Covid-19 cases from the East of England from February 26 to May 10, 2020. SARS-CoV-2 genomes were available for 700 care home residents from 292 care homes. By integrating genomic and temporal data, 409 viral clusters within 229 care homes were identified.

This indicated two different patterns, outbreaks among care home residents and independent introductions with limited onward transmission. The 10 care homes with the largest number of genomes contained 102/700 (14.6%) of all samples with genomic data available. For several of these 10 care homes, all cases clustered closely together on a phylogenetic tree, consistent with a single ‘outbreak’ spreading within the care home. By contrast, several care homes were ‘polyphyletic’, with cases distributed across the phylogenetic tree, consistent with multiple independent introductions of the virus among residents. However, the method does not assign probabilities for directionality of transmission and cannot determine precise person-to-person transmission chains.

Of the 694 care home residents with NHS numbers available, 398 (57.3%) were admitted to hospital with Covid-19. Forty of 694 (5.8%) cases were categorised as suspected hospital-acquired Covid-19 infections, defined as first positive test being 7 days or more after their hospital admission date and prior to their discharge date (N = 13) or within 7 days following their hospital discharge (N = 27). Of 694, 230 (33.1%) individuals were discharged from hospital within 7 days of their first positive test, and thus could potentially have been infectious at the time of hospital discharge.

Aggarwal et al., 2021, reviewed all genomic epidemiology studies on COVID-19 in long-term care facilities that had been published between January 1 and November 3, 2020. The only study included that analysed hospital discharge and outbreaks was Hamilton et al., 2021.

Public Health England, 2021, released a report assessing the contribution of hospital-associated Covid-19 infection to care home outbreaks in England. Outbreaks associated with hospital associated seeding were identified where the discharged patient was either the first case in an outbreak (index) or tested positive within the first 2 days of the outbreak.

Between January 30 and October 12, 2020, a total of 43,398 care home residents with a laboratory confirmed positive Covid-19 test result were identified. Of these, 35,740 (82.4%) were involved in an outbreak, equivalent to a total of 5,882 outbreaks. Precisely 1.6% (n=97) of outbreaks were identified as potentially seeded from hospital associated Covid-19 infection, with a total of 804 (1.2%) care home residents with confirmed infection associated with these outbreaks, and 286 deaths (2.1%). The majority of these potentially hospital-seeded care home outbreaks were identified in March to mid-April 2020. Of the 97 cases identified as potentially seeding care home outbreaks, 56 (58%) had a specimen date during their hospital stay, the remaining cases had their positive specimen within 14 days of their discharge.

Before April 15, testing in care homes was initially restricted to five symptomatic residents per care home to identify outbreaks (The Health Foundation, 2020). Therefore, due to limited availability of testing, other positive individuals who potentially seeded outbreaks could have been missed. The Public Health England report gives the percentage of outbreaks which were identified as potentially seeded from hospital associated Covid-19 infection from January 30 to October 2020.


Emmerson et al., 2021, describe a national cohort study of 3,115 hospital discharges to adult care homes in Wales between February 22 and June 27, 2020. A Cox proportional hazards regression model was used to assess the impact of time-dependent exposure to hospital discharge on incidence of the first known outbreak, over a window of 7-21 days after discharge, and adjusted for care home characteristics, including size and type of provision. Exposure to hospital discharge 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 = .29) after adjusting for care home characteristics. Care home size was the most significant predictor. The change in policy to mandate testing prior to discharge did not significantly alter hazard ratios.

However, the study does not rule out that in individual cases the source of the introduction to the care home could have been a hospital discharge. Furthermore, because the study has included all hospital discharges, the effect of the defined risk factor would have been diluted by non-risk discharges where the resident was not infected.


Public Health Scotland, 2020, released a report analysing discharges from NHS Scotland Hospitals to Care Homes. There were 3,599 discharges from hospital to a care home between March 1 and April 21, 2020. The majority of patients (81.9%) in this earlier period were not tested for Covid-19. Of the 650 who were tested, 78 received a positive result while in hospital. There were 1,605 discharges from hospital to a care home between April 22 and May 31. The majority (1,493, 93%) in this later period were tested for Covid-19. Of these, 1,215 tested negative and 278 tested positive. Of those who tested positive, 233 had a later negative test result before discharge.

843 of the 1084 care homes received 5,191 discharges between March 1 and May 31, 2020. Care homes received between 1 and 46 discharges, with an average of 6 discharges per care home. Using laboratory confirmed cases, 348 (32%) of care homes in Scotland experienced an outbreak of Covid-19 in the home between March 1 and June 21. Precisely 13.5% of care homes with no discharges from hospital had an outbreak, compared to 38% of care homes with one or more discharges.

Statistical modelling analysis showed that care home size has the strongest association with outbreaks of Covid-19. After accounting for care home size and other care home characteristics, the estimated risk of an outbreak related to hospital discharge reduces and is not statistically significant. The study suffers from the same limitations as Emmerson et al., 2021 by including non-risk discharges.

Reports of outbreaks in individual care homes

In addition to the studies described above, hospital discharges were sometimes mentioned in reports of the experience of individual long-term care facilities from the UK and other countries. However, due to inconsistent reporting on and investigation of the source of outbreaks in these reports, a comprehensive assessment of the extent to which outbreaks in long-term care facilities were associated with hospital discharges based on these reports is challenging. An example is the outbreak in a long-term care facility in London for people with severe epilepsy and other co-morbidities described by Balestrini et al., 2020. In this outbreak, a resident was symptomatic and admitted to hospital on March 5, 2020 but was discharged four days later after testing negative. They then tested positive two weeks later on March 23 and were transferred back to hospital. Three more cases in the same unit (one resident, two staff) were identified over the following 6 weeks, although a genomic investigation about the clustering of cases was not performed.

To cite this summary:

Byrd W, Salcher-Konrad M (2021) Evidence summary: What research is there linking hospital discharges to Covid-19 outbreaks in long-term care facilities? LTCcovid.org, International Long-Term Care Policy Network, CPEC-LSE, 22 October 2021.


Research carried out as part of the Social Care COVID Recovery and Resilience Project (funded by the National Institute for Health Research (NIHR) Policy Research Programme (NIHR202333). The views expressed in this summary are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care).


Aggarwal, D., Myers, R., Hamilton, W. L., Bharucha, T., Tumelty, N. M., Brown, C. S., Meader, E. J., Connor, T., Smith, D. L., Bradley, D. T., Robson, S., Bashton, M., Shallcross, L., Zambon, M., Goodfellow, I., Chand, M., O’Grady, J., Torok, M. E., Peacock, S. J., … Consortium, C.-19 G. U. K. (COG-U. (2021). The role of viral genomics in understanding COVID-19 outbreaks in long-term care facilities. The Lancet. Microbe. https://doi.org/10.1016/S2666-5247(21)00208-1

Balestrini, S., Koepp, M. J., Gandhi, S., Rickman, H. M., Shin, G. Y., Houlihan, C. F., Anders-Cannon, J., Silvennoinen, K., Xiao, F., Zagaglia, S., Hudgell, K., Ziomek, M., Haimes, P., Sampson, A., Parker, A., Helen Cross, J., Pardington, R., Nastouli, E., Swanton, C., … Sisodiya, S. M. (2020). Clinical outcomes of COVID-19 in long-term care facilities for people with epilepsy. Epilepsy & Behavior, 107602. https://doi.org/10.1016/j.yebeh.2020.107602

Byrd, W., Salcher-Konrad, M., Smith, S., & Comas-Herrera, A. (2021). What long-term care interventions and policy measures have been studied during the Covid-19 pandemic? Findings from a rapid mapping review of the scientific evidence published during 2020. https://ltccovid.org/2021/05/19/preprint-what-long-term-care-interventions-and-policy-measures-have-been-studied-during-the-covid-19-pandemic-findings-from-a-rapid-mapping-review-of-the-scientific-evidence-published-during-2020/

Emmerson, C., Adamson, J. P., Turner, D., Gravenor, M. B., Salmon, J., Cottrell, S., Middleton, V., Thomas, B., Mason, B. W., & Williams, C. J. (2021). Risk factors for outbreaks of COVID-19 in care homes following hospital discharge: A national cohort analysis. Influenza and Other Respiratory Viruses, 15(3), 371–380. https://doi.org/https://dx.doi.org/10.1111/irv.12831

Hamilton, W. L., Tonkin-Hill, G., Smith, E. R., Aggarwal, D., Houldcroft, C. J., Warne, B., Meredith, L. W., Hosmillo, M., Jahun, A. S., Curran, M. D., Parmar, S., Caller, L. G., Caddy, S. L., Khokhar, F. A., Yakovleva, A., Hall, G., Feltwell, T., Pinckert, M. L., Georgana, I., … Torok, M. E. (2021). Genomic epidemiology of COVID-19 in care homes in the east of England. ELife, 10. https://doi.org/10.7554/eLife.64618

Public Health England. (2021). A data linkage approach to assessing the contribution of hospital-associated SARS-CoV-2 infection to care home outbreaks in England, 30 January to 12 October 2020. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1005583/Nosocomial_Seeding_OF_care_home_outbreaks_report_Official_Sensitive-3.pdf

Public Health Scotland. (2020). Discharges from NHSScotland Hospitals to Care Homes between 1 March and 31 May 2020. https://beta.isdscotland.org/media/6224/2020-10-28-discharges-from-nhsscotland-hospitals-to-care-homes-report.pdf

The Health Foundation. (2020). Briefing: Adult social care and COVID-19. https://reader.health.org.uk/adult-social-care-and-covid-19-assessing-the-policy-response-in-england

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