A Molecular and Epidemiological Investigation of a Large SARS-CoV-2 Outbreak in a Long-Term Care Facility in Luxembourg, 2021

Abstract

In spring 2021, a long-term care facility (LTCF) of 154 residents in Luxembourg experienced a large severe, acute respiratory-syndrome coronavirus 2 (SARS-CoV-2) outbreak a few days after a vaccination campaign. We conducted an outbreak investigation and a serosurvey two months after the outbreak, compared attack rates (AR) among residents and staff, and calculated hospitalization and case-fatality rates (CFR). Whole genome sequencing (WGS) was performed to detect variants in available samples and results were compared to genomes published on GISAID. Eighty-four (55%) residents and forty-five (26%) staff members tested positive for SARS-CoV-2; eighteen (21%) residents and one (2.2%) staff member were hospitalized, and twenty-three (CFR: 27%) residents died. Twenty-seven (21% of cases) experienced a reinfection. Sequencing identified seventy-seven cases (97% of sequenced cases) with B.1.1.420 and two cases among staff with B.1.351. The outbreak strain B.1.1.420 formed a separate cluster from cases from other European countries. Convalescent and vaccinated residents had higher anti-SARS-CoV-2 IgG antibody concentrations than vaccinated residents without infection (98% vs. 52%, respectively, with >120 RU/mL, p < 0.001). We documented an extensive outbreak of SARS-CoV-2 in an LTCF due to the presence of a specific variant leading to high CFR. Infection in vaccinated residents increased antibody responses. A single vaccine dose was insufficient to mitigate the outbreak.

Epidemiology of COVID-19 outbreaks in aged care facilities during postvaccine period: a systematic review and meta-analysis

“…Articles not fulfilling selection criteria and an aggregated dataset containing non-extractable data were excluded from analysis (n=63) (figure 1). 20 Among the 38 included articles, 10 are from the USA, 5 from Italy, 5 from France, 5 from Germany, 3 from Canada, 3 from Spain and Netherlands, and 1 each from the UK, Japan, Serbia, Switzerland and Luxembourg 21–40 44 45 49–64. All studies are observational in nature and mostly, outbreaks were described over a period of 6 months (January–July 2021) (table 1).…”

“…25 studies reported a pooled hospitalisation rate of 17% (95% CI 13% to 23%, p<0.01) among the confirmed cases of which only 13 articles had information on the vaccination status of hospitalised cases (online supplemental file 1). 21–23 25–27 32 34–39 44 45 49 50 52 54–56 58 60 62 64 The hospitalisation rates were six times lower between vaccinated 4% (95% CI 2% to 7%, p<0.01) and unvaccinated residents 27% (95% CI 12% to 51%, p<0.01) after pooling available data from a total of 13 and 9 studies, respectively (online supplemental file 1). 21 25–27 38 44 58 62 Hospitalisation rates among the vaccinated confirmed cases 14% (95% CI 8% to 23%, p<0.01) declined almost three times lower compared with the unvaccinated confirmed cases 48% (95% CI 32% to 64%, p=0.14) (online supplemental file 1).…”