Research letter
SARS-CoV-2 Outbreaks in Care Homes for the Elderly and Disabled in Germany
A Comparative Epidemiological Analysis of the Periods Before and After the Beginning of the Vaccination Campaign
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Because of the high risk for residents of care homes for elderly and disabled people of contracting a severe or fatal SARS-CoV-2 infection, this group of persons and the employees in these institutions were among the first who were offered the option of COVID-19 vaccination at the start of the vaccination campaign in Germany at the end of December 2020. In spite of this, however, SARS-CoV-2 outbreaks in care homes for the elderly and disabled are still occurring. Since August 2021 (notification week [NW] 30/2021), an increasing trend in the number of outbreaks has been observed (1). We analyzed notification data to study in outbreaks in care homes for the elderly and disabled any changes in outbreak sizes (indicator for successful protection from infection) and changes in the severity of the outbreaks on the basis of hospitalizations and the case-fatality rates before and after most of the residents had been fully vaccinated.
Methods
We included in our analysis all notified outbreaks of SARS-CoV-2 with a minimum of two PCR confirmed SARS-CoV-2 cases in the setting “care homes for the elderly and disabled” between March 2020 (NW 09/2020) and December 2021 (NW 52/2021). We identified the age group ≥60 years as the best possible approximation for residents of care homes for the elderly and disabled (1), as in these outbreaks, cases in personnel, visitors, and their domestic environments are also counted, which enables comparable results with the weekly report on COVID-19 by the Robert Koch-Institute (RKI).
The size and severity of outbreaks were compared for the following phases of the pandemic: Phase 1, the time period before vaccinations (March 2020, NW 09/2020 to December 2020, NW 53/2020), Phase 2: start of vaccinations (January 2021, NW 01/2021 to April 2021, NW 14/2021), Phase 3: time period from which a majority of residents were fully initially immunized (data status 31 March 2021 first vaccination about 99% and second vaccination about 75% [2], between April 2021, NW 15/2021 and December 2021, NW 52/2021). We used logistic regression (odds ratio, OR) to study the trend in the number of deaths (outcome: “deceased”: yes/no) in SARS-CoV-2 outbreak cases, adjusted by hospitalization, sex, age group, and federal state while considering all phases. We used R (version x64 4.1.2) for all our analyses.
Results
The Figure shows outbreak cases in care homes for the elderly and disabled and the numbers of SARS-CoV-2 cases in the general population over time from NW 09/2020 to NW 52/2021.
In total, 7794 outbreaks with 177 696 outbreak cases (73.6% age group ≥60 years) were registered in care homes for the elderly and disabled (Table). The median number of outbreak cases was 14. The case-fatality rate among outbreak cases was 14.5% (19.5% age group ≥60 years among all outbreak cases ≥60 years). In Phase 1, 4124 outbreaks and 122 579 outbreak cases were notified, and in Phase 3, 1970 outbreaks and 25 206 outbreak cases. The median number of cases per outbreak fell from 21 to 8. The case-fatality rate fell from 15.7% to 10.0%; in the age group ≥60 years it fell from 21.1% to 13.6%. The rate of hospitalized patients remained near constant across all phases (11.7% versus 11.6%). The fall in case-fatality rates in outbreaks (all age groups) compared with Phase 1 (N=19 281) remained significant for Phase 2 (N=3948, adjusted OR [95% confidence interval=0.8 [0.8; 0.9]) and Phase 3 (N=2515, adjusted OR [95% CI]=0.5 [0.5; 0.6] compared with Phase 1.
Discussion
The notable fall in outbreak cases and deaths in residents of care homes for the elderly and disabled since the start of Phase 2 in spite of high SARS-CoV-2 incidence rates in the general population constitutes a crucial change from the dynamic in the same period of the previous year (3). It is possible that a delay in notification of COVID-19 deaths in Phase 3 contributed to an overestimate of the fall in the case-fatality rate. Possible reasons for the slightly rising outbreak numbers could be discussed in the context of waning immunity over time and the lower effectiveness of the vaccine vis-à-vis the Delta variant (4). However, the current situation is not comparable to that of the previous year as the rise in outbreaks is relatively lower and the case-fatality rate is also notably reduced.
In spite of high vaccination rates in residents of care homes for the elderly and disabled at the start of Phase 3, we have to assume differences in the vaccination situation between institutions (5). The Robert Koch Institute undertook nationwide vaccination monitoring in October 2021 and found that the rate of fully vaccinated residents ranged from only 28% to 100% (overall 89%) (5). We can assume that especially unvaccinated persons are disproportionally more often hospitalized and die.
The introduction of COVID-19 vaccination as well as further pharmaceutical and non-pharmaceutical measures have helped to reduce notably the size and severity of SARS-CoV-2 outbreaks in care homes for the elderly and disabled. In the setting of this ecological study, a causal association cannot be confirmed, but the close link between measures and case numbers make this seem probable.
The measures should continue to be used in care homes for the elderly and disabled to prevent severe disease courses in residents. This includes in particular greater vaccination coverage, the stringent implementation of recommendations for booster vaccinations, and the simultaneous adherence to high hygiene standards.
*The authors share joint first authorship
Dunja Said*, Beneditta Suwono*, Birgitta Schweickert, Viktoria Schönfeld, Tim Eckmanns, Sebastian Haller, Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin (Said, Suwono, Schweickert, Schönfeld, Eckmanns, Haller) saidd@rki.de
Conflict of interest statement
The authors declare that no conflict of interest exists.
Manuscript received on 2 February 2022, revised version accepted on 18 March 2022.
Translated from the original German by Birte Twisselmann, PhD.
Cite this as
Said D, Suwono B, Schweickert B, Schönfeld V, Eckmanns T, Haller S: SARS-CoV-2 outbreaks in care homes for the elderly and disabled in Germany—a comparative epidemiological analysis of the periods before and after the beginning of the vaccination campaign. Dtsch Arztebl Int 2022; 119: 486–7. DOI: 10.3238/arztebl.m2022.0170
