Evaluation of four laboratory-based high-throughput SARS-CoV-2 automated antigen tests compared to RT-PCR on nasal and oropharyngeal samples.

BACKGROUND: The demand for RT-PCR testing has been unprecedented during the SARS-CoV-2 pandemic. Fully automated antigen tests (AAT) are less cumbersome than RT-PCR, but data on performance compared to RT-PCR are scarce. METHODS: The study consists of two parts. A retrospective analytical part, comparing the performance of four different AAT on 100 negative and 204 RT-PCR positive deep oropharyngeal samples divided into four groups based on RT-PCR cycle of quantification levels. In the prospective clinical part, 206 individuals positive for and 199 individuals negative for SARS-CoV-2 were sampled from either the anterior nasal cavity (mid-turbinate) or by deep oropharyngeal swabs or both. The performance of AATs was compared to RT-PCR. RESULTS: The overall analytical sensitivity of the AATs differed significantly from 42% (95% CI 35-49) to 60% (95% CI 53-67) with 100% analytical specificity. Clinical sensitivity of the AATs differed significantly from 26% (95% CI 20-32) to 88% (95% CI 84-93) with significant higher sensitivity for mid-turbinate nasal swabs compared to deep oropharyngeal swabs. Clinical specificity varied from 97% to 100%. CONCLUSION: All AATs were highly specific for detection of SARS-CoV-2. Three of the four AATs were significantly more sensitive than the fourth AAT both in terms of analytical and clinical sensitivity. Anatomical test location significantly influenced the clinical sensitivity of AATs.

A Cross-Sectional Study of SARS-CoV-2 Antibodies and Risk Factors for Seropositivity in Staff in Day Care Facilities and Preschools in Denmark.

The aim of this study was to provide information about immunity against COVID-19 along with risk factors and behavior among employees in day care facilities and preschools (DCS) in Denmark. In collaboration with the Danish Union of Pedagogues, during February and March 2021, 47,810 members were offered a point-of-care rapid SARS-CoV-2 antibody test (POCT) at work and were invited to fill in an electronic questionnaire covering COVID-19 exposure. Seroprevalence data from Danish blood donors (total Ig enzyme-linked immunosorbent assay [ELISA]) were used as a proxy for the Danish population. A total of 21,018 (45%) DCS employees completed the questionnaire and reported their POCT result {median age, 44.3 years (interquartile range [IQR], [32.7 to 53.6]); females, 84.1%}, of which 20,267 (96.4%) were unvaccinated and included in analysis. A total of 1,857 (9.2%) participants tested seropositive, significantly higher than a seroprevalence at 7.6% (risk ratio [RR], 1.2; 95% confidence interval [CI], 1.14 to 1.27) among 40,541 healthy blood donors (median age, 42 years [IQR, 28 to 53]; males, 51.3%). Exposure at work (RR, 2.9; 95% CI, 2.3 to 3.6) was less of a risk factor than exposure within the household (RR, 12.7; 95% CI, 10.2 to 15.8). Less than 25% of participants reported wearing face protection at work. Most of the participants expressed some degree of fear of contracting COVID-19 both at work and outside work. SARS-CoV-2 seroprevalence was slightly higher in DCS staff than in blood donors, but possible exposure at home was associated with a higher risk than at work. DCS staff expressed fear of contracting COVID-19, though there was limited use of face protection at work. IMPORTANCE Identifying at-risk groups and evaluating preventive interventions in at-risk groups is imperative for the ongoing pandemic as well as for the control of future epidemics. Although DCS staff have a much higher risk of being infected within their own household than at their workplace, most are fearful of being infected with COVID-19 or bringing COVID-19 to work. This represents an interesting dilemma and an important issue which should be addressed by public health authorities for risk communication and pandemic planning. This study design can be used in a strategy for ongoing surveillance of COVID-19 immunity or other infections in the population. The findings of this study can be used to assess the need for future preventive interventions in DCS, such as the use of personal protective equipment.

SARS-CoV-2 Infection Rates Following Use of Regular Compared With Defective Respirators When Caring for COVID-19 Patients: A Retrospective Follow-up Study.

BACKGROUND: There is strong observational evidence that respirators are highly effective in protecting the users from being infected with Middle East respiratory syndrome and severe acute respiratory syndrome coronavirus (SARS-CoV), but the evidence for SARS-CoV-2 during daily work is limited. This study utilized a subset of healthcare workers' temporary use of a new brand respirator with frequent defects when caring for coronavirus disease 2019 (COVID-19) patients to assess the protective effect of regular respirators against SARS-CoV-2 infection. METHODS: We retrospectively followed 463 participants wearing a regular respirator and 168 wearing the new brand respirator day-by-day when caring for COVID-19 patients until testing polymerase chain reaction positive for SARS-CoV-2 between 27th December 2020 and 14th January 2021. RESULTS: We observed seven and eight incident SARS-CoV-2-infected cases. This corresponded with daily infection rates of 0.2 and 0.5%, an incidence rate ratio of 0.4 [95% confidence interval (CI) 0.1; 1.0], and an incidence rate difference of 0.3% (95% CI -0.1; 0.8) when comparing a regular with the new brand respirator. DISCUSSION: We regard the new brand respirator a sham intervention, and this study thus provides further evidence for the protective effect of respirators when exposed to SARS-CoV-2 virus.

Persistent Symptoms and Sequelae After Severe Acute Respiratory Syndrome Coronavirus 2 Infection Not Requiring Hospitalization: Results From Testing Denmark, a Danish Cross-sectional Survey.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with persistent symptoms ("long COVID"). We assessed the burden of long COVID among nonhospitalized adults with polymerase chain reaction (PCR)-confirmed SARS-CoV-2 infection. Methods: In the fall of 2020, a cross-sectional survey was performed in the adult Danish general population. This included a self-administered point-of-care test for SARS-CoV-2 antibodies, the Short Form Health Survey (SF-12), and coronavirus disease 2019 (COVID-19)-associated symptom questions. Nonhospitalized respondents with a positive SARS-CoV-2 PCR test ≥12 weeks before the survey (cases) were matched (1:10) to seronegative controls on age, sex, and body mass index. Propensity score-weighted odds ratios (ORs) and ORs for risk factors were estimated for each health outcome. Results: In total, 742 cases and 7420 controls were included. The attributable risk of at least 1 long-COVID symptom was 25.0 per 100 cases (95% confidence interval [CI], 22.2-27.4). Compared to controls, cases reported worse general health (OR, 5.9 [95% CI, 5.0-7.0]) and had higher odds for a broad range of symptoms, particularly loss of taste (OR, 11.8 [95% CI, 9.5-14.6]) and smell (OR, 11.2 [95% CI, 9.1-13.9]). Physical and Mental Component Summary scores were also significantly reduced with differences of -2.5 (95% CI, -3.1 to -1.8) and -2.0 (95% CI, -2.7 to -1.2), respectively. Female sex and severity of initial infection were major risk factors for long COVID. Conclusions: Nonhospitalized SARS-CoV-2 PCR-positive individuals had significantly reduced physical and mental health, and 1 in 4 reported persistence of at least 1 long-COVID symptom.

SARS-CoV-2 antibody prevalence among homeless people and shelter workers in Denmark: a nationwide cross-sectional study.

BACKGROUND: People experiencing homelessness (PEH) and associated shelter workers may be at higher risk of infection with "Severe acute respiratory syndrome coronavirus 2" (SARS-CoV-2). The aim of this study was to determine the prevalence of SARS-CoV-2 among PEH and shelter workers in Denmark. DESIGN AND METHODS: In November 2020, we conducted a nationwide cross-sectional seroprevalence study among PEH and shelter workers at 21 recruitment sites in Denmark. The assessment included a point-of-care test for antibodies against SARS-CoV-2, followed by a questionnaire. The seroprevalence was compared to that of geographically matched blood donors considered as a proxy for the background population, tested using a total Ig ELISA assay. RESULTS: We included 827 participants in the study, of whom 819 provided their SARS-CoV-2 antibody results. Of those, 628 were PEH (median age 50.8 (IQR 40.9-59.1) years, 35.5% female) and 191 were shelter workers (median age 46.6 (IQR 36.1-55.0) years and 74.5% female). The overall seroprevalence was 6.7% and was similar among PEH and shelter workers (6.8% vs 6.3%, p = 0.87); and 12.2% among all participants who engaged in sex work. The overall participant seroprevalence was significantly higher than that of the background population (2.9%, p < 0.001). When combining all participants who reported sex work or were recruited at designated safe havens, we found a significantly increased risk of seropositivity compared to other participants (OR 2.23, 95%CI 1.06-4.43, p = 0.02). Seropositive and seronegative participants reported a similar presence of at least one SARS-CoV-2 associated symptom (49% and 54%, respectively). INTERPRETATIONS: The prevalence of SARS-CoV-2 antibodies was more than twice as high among PEH and associated shelter workers, compared to the background population. These results could be taken into consideration when deciding in which phase PEH are eligible for a vaccine, as part of the Danish national SARS-CoV-2 vaccination program rollout. FUNDING: TrygFonden and HelseFonden.

Hand hygiene compliance among healthcare workers before and during the COVID-19 pandemic.

BACKGROUND: Healthcare workers' (HCWs) adherence to hand hygiene is vital in combatting COVID-19 in hospitals. We aimed to investigate HCWs hand hygiene compliance before and during the COVID-19 pandemic and hypothesised that hand hygiene compliance would increase during the pandemic. METHODS: We conducted a prospective observational study in three medical departments at the Regional Hospital of West Jutland, Denmark from April 2019 to August 2020. A total of 150 HCWs participated before the COVID-19 pandemic and 136 during the pandemic. Hand hygiene observations were assessed using an automated hand hygiene monitoring system. Students unpaired t-test was used to assess differences in hand hygiene compliance rates in each department. RESULTS: Comparison analyses showed, that hand hygiene compliance in department A and B was significantly higher before the COVID-19 pandemic than during the pandemic; a 7% difference in department A and a 5% difference in department B. For department C, the total hand hygiene compliance was unchanged during the pandemic compared to before. CONCLUSION: The COVID-19 pandemic did not raise hand hygiene compliance. Further studies are needed to verify these findings and further identify barriers to hand hygiene compliance among HCWs.

A Comparison of Pharyngeal Swabs and Tracheal Secretions for the Diagnosing of COVID-19.

The aim of this study was to compare the test results from patients who, within a short timescale, have been tested for COVID-19 using both a pharyngeal swab and tracheal secretion. Data were collected from the database of AUH, from patients hospitalized between 1 March 2020 and 1 March 2021 who, due to symptoms of COVID-19, were tested by a pharyngeal swab and by tracheal secretion. We found great agreement between oropharyngeal swab and tracheal secretion RT-PCR testing for the diagnosis of COVID-19, with 98.5% of double tests being concordant and only 1.5% being discordant. This finding may advocate a single-test strategy being either an oropharyngeal swab RT-PCR testing or tracheal secretion, although this study revealed 15.9% false negative oropharyngeal swabs.

Seroprevalence of SARS-CoV-2 antibodies in social housing areas in Denmark.

BACKGROUND: COVID-19 is thought to be more prevalent among ethnic minorities and individuals with low socioeconomic status. We aimed to investigate the prevalence of SARS-CoV-2 antibodies during the COVID-19 pandemic among citizens 15 years or older in Denmark living in social housing (SH) areas. METHODS: We conducted a study between January 8th and January 31st, 2021 with recruitment in 13 selected SH areas. Participants were offered a point-of-care rapid SARS-CoV-2 IgM and IgG antibody test and a questionnaire concerning risk factors associated with COVID-19. As a proxy for the general Danish population we accessed data on seroprevalence from Danish blood donors (total Ig ELISA assay) in same time period. RESULTS: Of the 13,279 included participants, 2296 (17.3%) were seropositive (mean age 46.6 (SD 16.4) years, 54.2% female), which was 3 times higher than in the general Danish population (mean age 41.7 (SD 14.1) years, 48.5% female) in the same period (5.8%, risk ratios (RR) 2.96, 95% CI 2.78-3.16, p > 0.001). Seropositivity was higher among males (RR 1.1, 95% CI 1.05-1.22%, p = 0.001) and increased with age, with an OR seropositivity of 1.03 for each 10-year increase in age (95% CI 1.00-1.06, p = 0.031). Close contact with COVID-19-infected individuals was associated with a higher risk of infection, especially among household members (OR 5.0, 95% CI 4.1-6.2 p < 0,001). Living at least four people in a household significantly increased the OR of seropositivity (OR 1.3, 95% CI 1.0-1.6, p = 0.02) as did living in a multi-generational household (OR 1.3 per generation, 95% CI 1.1-1.6, p = 0.003). Only 1.6% of participants reported not following any of the national COVID-19 recommendations. CONCLUSIONS: Danish citizens living in SH areas of low socioeconomic status had a three times higher SARS-CoV-2 seroprevalence compared to the general Danish population. The seroprevalence was significantly higher in males and increased slightly with age. Living in multiple generations households or in households of more than four persons was a strong risk factor for being seropositive. Results of this study can be used for future consideration of the need for preventive measures in the populations living in SH areas.

Long COVID symptoms and duration in SARS-CoV-2 positive children - a nationwide cohort study.

Most children have a mild course of acute COVID-19. Only few mainly non-controlled studies with small sample size have evaluated long-term recovery from SARS-CoV-2 infection in children. The aim of this study was to evaluate symptoms and duration of 'long COVID' in children. A nationwide cohort study of 37,522 children aged 0-17 years with RT-PCR verified SARS-CoV-2 infection (response rate 44.9%) and a control group of 78,037 children (response rate 21.3%). An electronic questionnaire was sent to all children from March 24th until May 9th, 2021. Symptoms lasting > 4 weeks were common among both SARS-CoV-2 children and controls. However, SARS-CoV-2 children aged 6-17 years reported symptoms more frequently than the control group (percent difference 0.8%). The most reported symptoms among pre-school children were fatigue Risk Difference (RD) 0.05 (CI 0.04-0.06), loss of smell RD 0.01 (CI 0.01-0.01), loss of taste RD 0.01 (CI 0.01-0.02) and muscle weakness RD 0.01 (CI 0.00-0.01). Among school children the most significant symptoms were loss of smell RD 0.12 (CI 0.12-0.13), loss of taste RD 0.10 (CI 0.09-0.10), fatigue RD 0.05 (CI 0.05-0.06), respiratory problems RD 0.03 (CI 0.03-0.04), dizziness RD 0.02 (CI 0.02-0.03), muscle weakness RD 0.02 (CI 0.01-0.02) and chest pain RD 0.01 (CI 0.01-0.01). Children in the control group experienced significantly more concentration difficulties, headache, muscle and joint pain, cough, nausea, diarrhea and fever than SARS-CoV-2 infected. In most children 'long COVID' symptoms resolved within 1-5 months. CONCLUSIONS: Long COVID in children is rare and mainly of short duration. WHAT IS KNOWN: • There are increasing reports on 'long COVID' in adults. • Only few studies have evaluated the long-term recovery from COVID-19 in children, and common for all studies is a small sample size (median number of children included 330), and most lack a control group. WHAT IS NEW: • 0.8% of SARS-CoV-2 positive children reported symptoms lasting >4 weeks ('long COVID'), when compared to a control group. • The most common 'long COVID' symptoms were fatigue, loss of smell and loss of taste, dizziness, muscle weakness, chest pain and respiratory problems. • These 'long COVID' symptoms cannot be assigned to psychological sequelae of social restrictions. • Symptoms such as concentration difficulties, headache, muscle- and joint pain as well as nausea are not 'long COVID' symptoms. • In most cases 'long COVID' symptoms resolve within 1-5 months.

Testing Denmark: a Danish Nationwide Surveillance Study of COVID-19.

"Testing Denmark" is a national, large-scale, epidemiological surveillance study of SARS-CoV-2 in the Danish population. Between September and October 2020, approximately 1.3 million people (age >15 years) were randomly invited to fill in an electronic questionnaire covering COVID-19 exposures and symptoms. The prevalence of SARS-CoV-2 antibodies was determined by point-of care rapid test (POCT) distributed to participants' home addresses. In total, 318,552 participants (24.5% invitees) completed the study and 2,519 (0.79%) were seropositive. Of the participants with a prior positive PCR test (n = 1,828), 29.1% were seropositive in the POCT. Although seropositivity increased with age, participants 61 years and over reported fewer symptoms and were tested less frequently. Seropositivity was associated with physical contact with SARS-CoV-2 infected individuals (risk ratio [RR] 7.43, 95% CI: 6.57-8.41), particular in household members (RR 17.70, 95% CI: 15.60-20.10). A greater risk of seropositivity was seen in home care workers (RR 2.09, 95% CI: 1.58-2.78) compared to office workers. A high degree of adherence with national preventive recommendations was reported (e.g., >80% use of face masks), but no difference were found between seropositive and seronegative participants. The seroprevalence result was somewhat hampered by a lower-than-expected performance of the POCT. This is likely due to a low sensitivity of the POCT or problems reading the test results, and the main findings therefore relate to risk associations. More emphasis should be placed on age, occupation, and exposure in local communities. IMPORTANCE To date, including 318,522 participants, this is the largest population-based study with broad national participation where tests and questionnaires have been sent to participants' homes. We found that more emphasis from national and local authorities toward the risk of infection should be placed on age of tested individuals, type of occupation, as well as exposure in local communities and households. To meet the challenge that broad nationwide information can be difficult to gather. This study design sets the stage for a novel way of conducting studies. Additionally, this study design can be used as a supplementary model in future general test strategy for ongoing monitoring of COVID-19 immunity in the population, both from past infection and from vaccination against SARS-CoV-2, however, with attention to the complexity of performing and reading the POCT at home.

Analysis of social interactions and risk factors relevant to the spread of infectious diseases at hospitals and nursing homes.

Ensuring the safety of healthcare workers is vital to overcome the ongoing COVID-19 pandemic. We here present an analysis of the social interactions between the healthcare workers at hospitals and nursing homes. Using data from an automated hand hygiene system, we inferred social interactions between healthcare workers to identify transmission paths of infection in hospitals and nursing homes. A majority of social interactions occurred in medication rooms and kitchens emphasising that health-care workers should be especially aware of following the infection prevention guidelines in these places. Using epidemiology simulations of disease at the locations, we found no need to quarantine all healthcare workers at work with a contagious colleague. Only 14.1% and 24.2% of the health-care workers in the hospitals and nursing homes are potentially infected when we disregard hand sanitization and assume the disease is very infectious. Based on our simulations, we observe a 41% and 26% reduction in the number of infected healthcare workers at the hospital and nursing home, when we assume that hand sanitization reduces the spread by 20% from people to people and 99% from people to objects. The analysis and results presented here forms a basis for future research to explore the potential of a fully automated contact tracing systems.

Electronic reporting of diagnostic laboratory test results from all healthcare sectors is a cornerstone of national preparedness and control of COVID-19 in Denmark.

The COVID-19 pandemic has led to an unprecedented demand for real-time surveillance data in order to inform critical decision makers regarding the management of the pandemic. The aim of this review was to describe how the Danish national microbiology database, MiBa, served as a cornerstone for providing data to the real-time surveillance system by linkage to other nationwide health registries. The surveillance system was established on an existing IT health infrastructure and a close network between clinical microbiologists, information technology experts, and public health officials. In 2020, testing capacity for SARS-CoV-2 was ramped up from none to over 10,000 weekly PCR tests per 100,000 population. The crude incidence data mirrored this increase in testing. Real-time access to denominator data and patient registries enabled adjustments for fluctuations testing activity, providing robust data on crude SARS-CoV-2 incidence during the changing diagnostic and management strategies. The use of the same data for different purposes, for example, final laboratory reports, information to the public, contact tracing, public health, and science, has been a critical asset for the pandemic response. It has also raised issues concerning data protection and critical capacity of the underlying technical systems and key resources. However, even with these limitations, the setup has enabled decision makers to adopt timely interventions. The experiences from COVID-19 may motivate a transformation from traditional indicator-based public health surveillance to an all-encompassing information system based on access to a comprehensive set of data sources, including diagnostic and reference microbiology.

Light-guided nudging and data-driven performance feedback improve hand hygiene compliance among nurses and doctors.

BACKGROUND: Evidence-based practices to increase hand hygiene compliance (HHC) among health care workers are warranted. We aimed to investigate the effect of a multimodal strategy on HHC. METHODS: During this 14-month prospective, observational study, an automated monitoring system was implemented in a 29-bed surgical ward. Hand hygiene opportunities and alcohol-based hand rubbing events were measured in patient and working rooms (medication, utility, storerooms, toilets). We compared baseline HHC of health care workers across periods with light-guided nudging from sensors on dispensers and data-driven performance feedback (multimodal strategy) using the Student's t test. RESULTS: The doctors (n = 10) significantly increased their HHC in patient rooms (16% vs 42%, P< .0001) and working rooms (24% vs 78%, P= .0006) when using the multimodal strategy. The nurses (n = 26) also increased their HHC significantly from baseline in both patient rooms (27% vs 43%, P = .0005) and working rooms (39% vs 64%, P< .0001). The nurses (n = 9), who subsequently received individual performance feedback, further increased HHC, compared with the period when they received group performance feedback (patient rooms: 43% vs 55%, P< .0001 and working rooms: 64% vs 80%, P< .0001). CONCLUSIONS: HHC of doctors and nurses can be significantly improved with light-guided nudging and data-driven performance feedback using an automated hand hygiene system.