key: cord-0743138-2gygrm39
authors: Foley, M. K.; Searle, S. D.; Toloue, A.; Booth, R.; Falkenham, A.; Falzarano, D.; Rubino, S.; Francis, M.; McNeil, M.; Richardson, C.; LeBlanc, J. J.; Oldford, S.; Gerdts, V.; Andrew, M. K.; McNeil, S.; Clarke, B.; Rockwood, K.; Kelvin, D. J.; Kelvin, A. A.
title: Centenarians and extremely old people living with frailty can elicit durable SARS-CoV-2 spike specific IgG antibodies with virus neutralization functions following virus infection
date: 2021-03-08
journal: nan
DOI: 10.1101/2021.03.05.21252707
sha: e02892ca194513fcbaf1342b25df2d76f5608978
doc_id: 743138
cord_uid: 2gygrm39

Background The SARS-CoV-2 (Severe Acute Respiratory Syndrome coronavirus 2) has led to more than 114 million COVID-19 cases and over 2.5 million deaths worldwide. Epidemiological analysis has revealed that the risk of developing severe COVID-19 increases with age. Despite a disproportionate number of older individuals and long-term care facilities being affected by SARS-CoV-2 and COVID-19, very little is understood about the immune responses and development of humoral immunity in the extremely old person after SARS-CoV-2 infection. Here we investigated the development of humoral immunity in centenarians following a SARS-CoV-2 outbreak in a long-term care facility. Methods Extreme aged individuals and centenarians who were residents in a long-term care facility and infected with or exposed to SARS-CoV-2 were investigated for the development of antibodies to SARS-CoV-2. Blood samples were collected from positive and bystander individuals 30 and 60 days after original diagnosis of SARS-CoV-2 infection. Plasma was used to quantify IgG, IgA, and IgM isotypes and subsequent subclasses of antibodies specific for SARS-CoV-2 spike protein. The function of anti-spike was then assessed by virus neutralization assays against the native SARS-CoV-2 virus. Findings Fifteen long-term care residents were investigated for SARS-CoV-2 infection. All individuals had a Clinical Frailty scale score greater than 5 and were of extreme older age or were centenarians. Six women with a median age of 98.8 years tested positive for SARS-CoV-2. Anti-spike IgG antibody titers were the highest titers observed in our cohort with all IgG positive individuals having virus neutralization ability. Additionally, 5 out of the 6 positive participants had a robust IgA anti-SARS-CoV-2 response. In all 5, antibodies were detected after 60 days from initial diagnosis. Interpretation Extreme older frail individuals and centenarians were able to elicit robust IgG and IgA antibodies directed toward SARS-CoV-2 spike protein. The antibodies were able to neutralize the virus. Humoral responses were still detectable after 60 days from initial diagnosis. Together, these data suggest that recovered participants who are of extreme old age would be protected if re-exposed to the same SARS-CoV-2 viral variant. Considering the threat of SARS-CoV-2 and COVID-19 to older age groups and long-term care facilities, the humoral responses to SARS-CoV-2 in older age groups is of public health importance and has implications to vaccine responses. Funding Canadian Institutes of Health Research (CIHR), NIH/NIAID, Genome Atlantic. VIDO receives operational funding from the Canada Foundation for Innovation through the Major Science Initiatives Fund and by Government of Saskatchewan through Innovation Saskatchewan.

The SARS-CoV-2 (Severe Acute Respiratory Syndrome coronavirus 2) has led to more than 114 million COVID-19 cases and >2.5 million deaths worldwide. Epidemiological analysis has revealed that the risk of developing severe COVID-19 increases with age. Despite a disproportionate number of older individuals and long-term care facilities being affected by SARS-CoV-2 and COVID-19, very little is understood about the immune responses and development of humoral immunity in the extremely old person after SARS-CoV-2 infection. Here we investigated the development of humoral immunity in centenarians following a SARS-CoV-2 outbreak in a longterm care facility.

Extreme aged individuals and centenarians who were residents in a long-term care facility and infected with or exposed to SARS-CoV-2 were investigated for the development of antibodies to SARS-CoV-2. Blood samples were collected from positive and bystander individuals 30 and 60 days after original diagnosis of SARS-CoV-2 infection. Plasma was used to quantify IgG, IgA, and IgM isotypes and subsequent subclasses of antibodies specific for SARS-CoV-2 spike protein. The function of anti-spike was then assessed by virus neutralization assays against the native SARS-CoV-2 virus.

Fifteen long-term care residents were investigated for SARS-CoV-2 infection. All individuals had a Clinical Frailty scale score ³5 and were of extreme older age or were centenarians. Six women with a median age of 98.8 years tested positive for SARS-CoV-2. Anti-spike IgG antibody titers were the highest titers observed in our cohort with all IgG positive individuals having virus . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

In December 2019, a novel coronavirus was identified in Wuhan, Hubei China, which has led to a devastating pandemic (WHO pandemic) 1,2 . Coronavirus disease 2019 (COVID-19) is used to define the clinical symptoms that are associated with infection from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 3 . The SARS-CoV-2 is an enveloped positive-sense, single-stranded RNA genome and belongs to the Coronaviridae family in the genus Betacoronavirus, sharing the same lineage (Lineage B) as the 2002 SARS-CoV 4 . The spike protein of SARS-CoV-2 is an external binding protein, which guides the virus to attach to a host cell and bind the angiotensin converting enzyme II receptor (ACE2) 5 . The spike protein is the primary immunogenic target for virus neutralization and vaccine design, due to its critical role in the virus life cycle 5 .

As the clinical cases of SARS-CoV-2 infection were analyzed, it was clear that signs and symptoms, clinical manifestations, and disease severity widely varies 6, 7 . Certain host factors have been linked to the development of severe COVID-19 resulting in pneumonia, acute respiratory distress syndrome (ARDS), and multi-organ failure 8, 9 . In particular, age has been identified as a risk factor for severe illness and death with the elderly population being most susceptible 8 . It is suspected that age-related changes to the immune system, including immunosenescence and 'inflamma-aging' as well as the increased susceptibilty to co-morbidies, may contribute to increased risk of severe COVID-19 in older individuals 10, 11 . Additionally, those at the highest risk are older adults residing in long-term care homes 12, 13 due to the increased number of individuals living in one area 12 , asymptomatic transmission [14] [15] [16] , atypical symptom presentation in older people 12, 15 , and the high burden of chronic illnesses 12, 17 . Although older individuals are heavily represented in COVID-19 case fatalities, the clinical course and immune responses of older persons to SARS-CoV-2 infection is poorly understood 11 .

Here, we examine a cohort of extreme old residents of a long-term care home that experienced a COVID-19 outbreak in Nova Scotia, Canada, with a focus on a group of centenarians who were infected with SARS-CoV-2. The humoral response and durability of antibody production following SARS-CoV-2 infection is currently ill-defined although multiple reports have documented a . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) spectrum of responses in several cohorts. The role of age as a cofactor in establishing protection against future SARS-CoV-2 re-exposure and reinfection is of considerable interest in aged individuals. We investigated the antibody responses to SARS-CoV-2 infection in a small group of extreme aged individuals to better understand how the aged immune system works to protect against SARS-CoV-2 infection.

At this time, we are not aware of any reports on the seroconversion ability, durability, antibody function or antibody isotype landscape of centenarians infected with SARS-CoV-2. There are many studies in non-centenarians in which neutralizing antibodies have been detected in convalescent participant plasma, with primary focus on IgG and IgM titres post SARS-CoV-2 infection. It is well documented that long-term care facilities and older individuals are more susceptible to severe outcomes of SARS-CoV-2 infection and COVID-19, but little is understood regarding the older individual's immune response to the virus during infection.

To our knowledge, this is the first study investigating seroconversion in SARS-CoV-2 infected centenarians residing in long-term care. Our study demonstrates that an aged immune system is still capable of mounting an antibody response to SARS-CoV-2 infection and that the antibodies elicited have virus neutralizing ability. Our data suggests that older and frail individuals, such as those in our study, have the capacity to be protected from a second infection with SARS-CoV-2.

. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted March 8, 2021.

The findings demonstrate that serconversion tests could be used to diagnose previous viral infection, outbreaks, and assess possible immune protection in an accessible and efficient manner. Serology analysis of older individuals displaying aberrant clinical COVID-19 could be used for case tracking and contact tracing in long-term cares home which are known to experience increased transmission Further, our data has implications for vaccine effectiveness in older individuals.

Residents of a non-profit long-term care (LTC) home in Halifax, Nova Scotia, between April and June 2020 where a widespread outbreak of SARS-CoV-2 occurred, were recruited to the study. Residents of the facility had single or double rooms. All residents of the LTC facility were considered exposed to the virus due to the widespread nature of the outbreak within the facility.

Consenting participants were enrolled, and testing was performed using routine practices.

Briefly, a flocked nasopharyngeal (NP) swab was collected in 3 mL universal transport media (Copan Diagnostics Inc., Murrieta, CA), or a combined oropharynx and anterior nares (OP/Na) swab was collected using the Aptima Multitest swab in 2.9 mL of specimen transport medium (Hologic, Inc., San Diego CA). NP or OP/Na swabs were subjected to real-time RT-PCR using the SARS-CoV-2 assay on a Cobas 6800 system (Roche Diagnostics, Mississauga, Ontario, Canada) per the manufacturer's instructions, or using a Total Nucleic Acid (TNA) extraction on a MagNApure . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) Twice a year, residents of Northwood each receive an update to their long-term care comprehensive Geriatric Assessment 19 . It includes a Clinical Frailty Scale score 20 . The CFS is a wellvalidated measure which categorizes frailty from fit to severely frail. Here we extracted information for analysis: age, sex, frailty, comorbidities, BMI (body mass index), and time between identification of the positive SARS-CoV-2 RT-RNA PCR test and blood collection 21 . A clinical description of the cohort is summarized in Table 1 .

Peripheral blood was collected from study participants in K2EDTA spray coated tubes (Fisher 367861). Blood samples were immediately transported to the laboratory and centrifuged for 10 m at 200 x g after collection. Plasma was isolated and stored in conical vials (Fisher 1495949B) at -80 o C until assays were performed.

To acquire SARS-CoV-2 Spike (S) protein for molecular assays, a truncated S (NCBI data base reference sequence (NC_045512.2)) was cloned into pDSG-IBA 103 Expression Vector. The furin cleavage site was mutated and the cloned product was validated by DNA sequencing at Genewiz (South Plainfield, New Jersey, USA). For S protein production, Mexi293E cells were grown in 6 well cell culture plates. For transfection, 3 µg of plasmid was diluted in 150 µl serumfree OptiMEM. In a separate tube, 10 µl of Polyethyleneimine (PEI) (1mg/ml) was diluted in 150 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted March 8, 2021. ; https://doi.org/10.1101/2021.03.05.21252707 doi: medRxiv preprint µl Opti-MEM, vortexed briefly, and incubated for 5 m. The two solutions were combined, gently vortexed, and then incubated for 20 m. Culture media on the cells was replaced with DMEM + 5% FBS, and the PEI/DNA mixture was added. After incubation for 72 h at 37 o C in a 5% CO2 chamber, recombinant S protein was harvested in cell culture media. S protein was purified using the IBA Strep-Tactin XT® Superflow® High Capacity resin system. Purified S protein was then used for ELISA assays. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 8, 2021. ; https://doi.org/10.1101/2021.03.05.21252707 doi: medRxiv preprint Reader (BTSLXFATS). Samples were considered positive if average optical density (OD) was greater than 0.1 and greater than the mean OD in SARS-CoV-2 unexposed samples plus 3 standard deviations at the same dilution. Negative samples are denoted as "1" for display on a logarithmic scale.

The SARS-CoV-2 strain SARS-CoV-2/Canada/ON/VIDO-01-2020 was used for in vitro . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 8, 2021.

The diluted virus was added to diluted plasma samples and incubated at 37 o C for one hour. A back titer of the virus was also prepared to confirm the titer of the virus dilution used. The plasma-virus mixture was added to plated Vero 76 cells and incubated at 37 o C in a 5% CO2 chamber for 1 h for virus absorption. The mixture was removed and replaced with vDMEM and placed back at 37 o C with 5% CO2 for 3 days. Cells were checked daily for signs of cytopathic effect (CPE), and results were recorded on day 5 post inoculation. Antibody titer was calculated as the inverse of the most diluted sample where no CPE was detected. All work with SARS-CoV-2 live virus was performed in a CL3 facility at VIDO.

Results were analysed using GraphPad Prism8.

Ethics for this study was approved by the IRB at Dalhousie University and is covered under the protocol "Sentinel surveillance for severe outcomes of laboratory-confirmed influenza in adults for the annual influenza season and for confirmed and suspected cases of COVID-19/SARS-CoV-2 acute respiratory disease" REB#1020727.

The sponsors had no role in the analysis or interpretation of the data. Alyson Kelvin had full access to all the data analysis and can take responsibility for all aspects of the paper.

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The copyright holder for this preprint this version posted March 8, 2021. ; https://doi.org/10.1101/2021.03.05.21252707 doi: medRxiv preprint A total of 15 SARS-CoV-2 exposed residents of a non-profit long-term care (LTC) facility were included. Their mean age was 96.9 (range 84 -103). All residents of the LTC facility were considered exposed as their rooms were on floors with positive participants. All residents including these participants (12 women and 3 men) were routinely screened for SARS-CoV-2 infection by nasopharyngeal swabbing and subsequent qRT-PCR for the RNA encoding the SARS-CoV-2 nucleoprotein (NP) ( Table 1) (Table 1 ). As expected, there was a high burden of dementia and frailty in the study population. For plasma sample collection, the mean time from PCR diagnosis with COVID-19 to sample collection was 30 days. For residents with a second blood sample collected, the mean time between the first and second blood collection was 30 days.

An enzyme-linked immunosorbent assay (ELISA) was used to detect the presence of antibodies directed toward the SARS-CoV-2 S protein present in the first blood collection for each resident enrolled in the study. Subsequently, the isotype and subclasses of S antibodies were identified by ELISA as well. SARS-CoV-2 infected centenarians had high titres of S-directed IgG in their plasma, with endpoint titers ranging from 1:6400-1:52400 (Figure 1Ai and C) . We were not . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 8, 2021. ; https://doi.org/10.1101/2021.03.05.21252707 doi: medRxiv preprint able to detect S-directed IgG in the plasma of SARS-CoV-2 NP PCR negative participants (Figure   1Aii and C) . Non-centenarians who tested PCR positive also had significant anti-S IgG endpoint titers (1:800) (Figure 1Bi and C) . Antibody IgG subclass analysis indicated that both IgG1 and IgG3

S-directed antibodies were present in centenarian residents 862 and 916 and the noncentenarian residents (Supplemental Figure 1 and 2) . Further isotype characterization revealed that all SARS-CoV-2 PCR positive centenarians had a detectable anti-S IgM response, with titres ranging from 1:400-1:6400 (Figure 2Ai ) similar to positive non-centenarians with the exception of one positive non-centenarian who did not have detectable anti-S IgM (Figure 2Aii ) summarized in Figure 2C . To complete the isotype analysis, S directed IgA antibodies were also measured in plasma samples where IgA1 anti-S levels were greater than IgA2 (Supplemental Figure 2 and 3) .

The SARS-CoV-2 positive centenarians were also positive for S IgA (1:800-1:25600) (Figure 3) . To determine if the humoral responses to the SARS-CoV-2 virus were similar in magnitude between infected centenarian and non-centenarian older residents, we directly compared if the titres of S directed IgG, IgM, and IgA of the two groups. The titers of S directed IgG, IgM, and IgA were not statistically different between the groups, demonstrating that advanced age did not alter Sdirected antibody elicitation to the SARS-CoV-2 virus.

To investigate the durability and function of antibodies elicited toward SARS-CoV-2, we analyzed a second blood sample collected approximately 30 days after the first draw to determine levels of S antibodies and whether antibodies had viral neutralization capacity. For the durability assay, resident 916 had consistently high levels of anti-S IgG titres with levels of 1:52400 still observed in their second plasma sample ( Figure 4A) . Conversely, the titer of resident . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. Together, our data illustrates that centenarians infected with SARS-CoV-2 were able to elicit SARS-CoV-2 S-directed neutralizing antibodies, demonstrating an intact humoral immune response.

To our knowledge, this is the first study investigating seroconversion in SARS-CoV-2 infected extreme aged adults, some over 100 years of age, residing in a long-term care facility.

Here, a group of highly aged, frail residents, the majority being female, residing in a long-term care facility who were infected with SARS-CoV-2 and survived, is described. The centenarians were able to elicit a successful S directed antibody response which was able to functionally neutralize the native SARS-CoV-2 virus. This work demonstrates that the extreme aged immune . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. 13, 20 . Aged immune systems are characterized not only by immunosenescence, where the immune system deteriorates with time 12 , but also inflammaging, chronic, low-grade inflammation which can contribute to disease pathogenesis 10 . The weakened immune system in older adults has led to concern with their ability to mount a successful humoral immune response to SARS-CoV-2 infection considering their increased susceptibility to the virus.

Here, we showed that after an average of 30 days after a positive SARS-CoV-2 NP PCR test, some extremely old LTC residents mounted high SARS-CoV-2 S-directed antibody responses across relevant immunoglobulin isotypes. The highest titers were observed with IgG, where centenarian titres ranged from 1:6400 to 1:52400, which is associated with neutralization function 30 days post symptom onset at titers ranging from 1:20 to 1:160. Other studies have established ELISA IgG titres of 1:320 as moderate and titres of 1:960 and above as high 25 , . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 8, 2021. ; https://doi.org/10.1101/2021.03.05.21252707 doi: medRxiv preprint demonstrating that the centenarians in this study induced a robust anti-spike IgG response after SARS-CoV-2 infection. Interestingly, one study by Klein and colleagues indicated that serum SARS-CoV-2 antibody titers increased with age and male sex in COVID-19 patients 26 . Since most of our advanced aged participants were female, our data suggests that extreme aged females also elicit high SARS-CoV-2 antibody titers. As well, our data demonstrate that even the most vulnerable members of the oldest old can mount an immune response and survive SARS-CoV-2 infection. In . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 8, 2021. ;  In contrast to our IgG anti-S findings, we found a robust early increase in S-specific plasma IgA in 5/6 SARS-CoV-2 infected people studied at 30 days post positive PCR test which declined.

Few studies have characterized the onset of IgA after SARS-CoV-2 infection in plasma, most likely due to the mucosal association typically considered for the IgA isotype. One study that examined COVID-19 convalescent plasma found a correlation of S-specific IgG with S-specific IgA in plasma 26 , as did we. Also, in agreement with our findings, another study found that plasma anti-S IgA is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 8, 2021. ; https://doi.org/10.1101/2021.03.05.21252707 doi: medRxiv preprint provide mechanisms for identifying an outbreak in extreme older individuals who may be unaware of their health status which is confounded by an atypical COVID-19 clinical picture.

Another concern surrounding the immune response to SARS-CoV-2 in adults is the concept of cross-reactivity to the virus due to infection with other coronaviruses across the life span. Studies using highly-sensitive flow-cytometry based methods have shown that people who were not exposed to SARS-CoV-2 had detectable IgG antibodies against the spike protein of virus.

These antibodies were especially prevalent in children and adolescents 30 . Studies have also shown that unexposed people have pre-existing CD4+ memory T cells that are reactive to common cold coronaviruses such as NL63, HKU1, and OC43, as well as the current pandemic coronavirus SARS-CoV-2 31 . As the participants studied in this cohort were highly aged and had likely been exposed to many viruses across their lifespans, it was hypothesized that some crossreactivity to the SARS-CoV-2 spike protein or virus may be observed. Interestingly, in our study, residents who did not test positive for SARS-CoV-2 RNA did not have any detectable plasma IgG against the SARS-CoV-2 spike protein. Our method of detection using indirect ELISA for IgG may suggest that cross-reactive antibodies from previous circulating common cold coronaviruses may not be an issue when screening individuals for serological evidence of a SARS-CoV-2 infection.

Our study was limited by a small sample size, lack of continued plasma sampling, and uncertain SARS-CoV-2 inoculation/exposure date. The low sample size reflects a low incidence rate in Nova Scotia, even among extremely old people living with frailty (cumulative confirmed cases were 177 per million on April 1 and 1057 by May 15, the period of initial data collection) 32 .

Even so, the information gathered here is extremely valuable because of the rare occurrence of . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 8, 2021. centenarians infected with SARS-CoV-2. The second timepoint for blood collection was not available for all residents studied, making it difficult to form more robust and broad conclusions from our data. Although more frequent blood collection would have been beneficial to better model the dynamics of the antibody response following infection in highly aged people, access to blood samples in this age group will remain a difficult task due to their vulnerability and the pragmatics of venipuncture. Finally, as with most viral infections, pinpointing the exact inoculation date or event for an infection is difficult in people. With increased studies following contact tracing and symptom onset as well as studies such as ours describing time from symptom onset and development of SARS-CoV-2 antibodies, a clearer clinical picture of disease progression and immune responses for extreme older adults as well as other age groups will be better defined.

The current COVID-19 pandemic has highlighted the often marked frailty of residents in longterm care which is evident by the high COVID-19 case numbers, COVID-19 fatalities, and SARS-CoV-2 outbreaks in these facilities across several countries [33] [34] [35] [36] [37] . The cause of this may be multifaceted, which may include the inadequacies of infection control measures and gaps in education as well as the difficulty identifying atypical clinical manifestations of COVID-19 in older people. Our study shows that even the oldest people can elicit a strong humoral response to SARS-CoV-2 and recover from infection. These findings are important for developing serological testing protocols as well as investigating the poor COVID-19 outcomes associated with LTC facilities.

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The copyright holder for this preprint this version posted March 8, 2021 We acknowledge the gracious help by Dr. Lisa Barrett with the study design, cohort management, and sample acquisition. We wish to thank all of the study participants for their involvement. This article is published with the permission of the Director of VIDO-InterVac with article number 932. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted March 8, 2021. ;  gene N (Ai); centenarians PCR negative for SARS-CoV-2 nucleic acid encoding gene N (Aii); noncentenarians PCR positive for SARS-CoV-2 nucleic acid encoding gene N (Bi); non-centenarians PCR negative for SARS-CoV-2 nucleic acid encoding gene N (Bii). Endpoint titers for each group are summarized and compared (C). is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted March 8, 2021. ; Table 1 All Participants SARS-CoV-2 Negative SARS-CoV-2 Positive N 15 9 6 Age, mean (SD) 96.9 (6.0) 95.6 (7.0) 98.8 (3.7) Women, n (%) 12 (80.0) 6 (66.7) 6 (100.0) Clinical Frailty Scale, mean (SD) 6 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. 

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term care residents 30 days after initial SARS-CoV-2 positive PCR tests or virus exposure were analyzed for IgG subclasses IgG1 (A) and IgG3 (B).

Clinical data from SARS-CoV-2 exposed and infected extreme aged residents of a longterm care facility.