key: cord-0762281-g4pz7cqm
authors: Herzberg, Jonas; Vollmer, Tanja; Fischer, Bastian; Becher, Heiko; Becker, Ann-Kristin; Sahly, Hany; Honarpisheh, Human; Guraya, Salman Yousuf; Strate, Tim; Knabbe, Cornelius
title: A Prospective Sero-epidemiological Evaluation of SARS-CoV-2 among Health Care Workers in a German Secondary Care Hospital
date: 2020-10-16
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2020.10.026
sha: 15cdb7ec3c0eb6383596c5cc0b3e10aacb18982e
doc_id: 762281
cord_uid: g4pz7cqm

OBJECTIVES: SARS-CoV-2 causing the pulmonary disease COVID-19 has challenged healthcare facilities worldwide. The sustainability of healthcare systems is largely reliant on the health status of their health care workers (HCW). This study was aimed at the detection of SARS-CoV-2 virus and specific antibodies among HCW in a German hospital, as a model system for the potential spread of the pandemic. METHODS: Between March and June 2020, we performed this study using a combination of RT-PCR test for the detection of SARS-CoV-2 RNA, and ELISA to detect the presence of anti-SARS-CoV-2 immunglobulin G (IgG) antibodies among HCW in a German hospital by repetitive oropharyngeal swabs (OPS) and blood samples. RESULTS: A total of 871/1081 employees participated in this prospective longitudinal study. During the study period of 9 weeks, 5329 OPS and 2136 blood samples were analyzed. In three participants (0.34%) SARS-CoV-2 RNA was detected. Anti-SARS-CoV-2-IgG antibodies were detected in 38 (4.36%) participants. CONCLUSION: Our study reports low prevalence of COVID-19 in HCW, which may reflect the effectiveness of hygiene protocols. It might, however, indicate a low prevalence of SARS CoV-2 in hospital employees. Our study protocol may serve as a thought-provoking example for future pandemic containment protocols in hospitals.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which results in the pulmonary disorder coronavirus disease 2019 (COVID-19) has been spreading since late 2019 throughout China and now worldwide. It is causing thousands of deaths around the world, with the numbers continuing to increase. Most recent reports suggest the number of cases has increased by up to 291,825 per day to a total of more than 25 million cases as of the end of August.(World Health Organization) This pandemic has created challenges for global healthcare systems and has forced a rapid increase in hospital total capacities and especially strained intensive care unit and ventilation capacities. (Phua et al. 2020 ) This situation has also showed the importance of health care workers in handling the increased number of patients.(The Lancet 2020)

The transmission of SARS-CoV-2 is reported to be mainly person-to-person by dropletinfection. (Hoehl et al. 2020) Due to this, health care workers (HCW) fall into a high risk group as they have close person-to-person contact including contact with COVID-19 patients. In addition, many SARS-CoV-2-positive individuals have no or very few symptoms, particularly in previously healthy individuals. (Mizumoto et al. 2020a; Rothe et al. 2020 ) These individuals are suspected to contribute to the rapidly increasing case numbers. (Li et al. 2020a; Mizumoto et al. 2020b) To prevent so called "patient-to-staff transmission" strict hygiene protocols are enforced in most hospitals. (Korth et al. 2020 ) Additionally within Germany rapid societal protective measures such as social distancing, wearing of face masks, and lockdown were quickly established and in place up till 22 March 2020 and subsequently slowly relaxed due to J o u r n a l P r e -p r o o f a decreased infection rate. There was, however, some interregional variability with regards to specifics of the societal protective measures the restrictions and protection plans differed from one region to another and even from one hospital to another.

This high-risk work environment has led to a feeling of precariousness for many HCW. (Canova et al. 2020) The perception that hospitals are high risk areas has also resulted in delays in patients seeking treatment in emergency situations (such as heart attack and stroke). (Bersano et al. 2020; De Rosa et al. 2020) Due to these perceptions, there is an unknown number of deaths resulting from the fear of a SARS-CoV-2-infection.

Moreover, as laid out in the international literature to date, sufficient clinical data about the dissemination in the normal population versus HCW is insufficient. Existing data only shines a spot-light of prevalence in either a small or mid-size group of people. (Wölfel et al.) To address this problem, more representative longitudinal studies are needed and first results of such longitudinal studies are published recently. (Behrens et al. 2020b (Behrens et al. , 2020a To evaluate the longitudinal spreading in a secondary care mid-sized hospital during different stages of restrictions, a prospective trial was initiated. Although doctors and nurses would be overrepresented in this trial, it did include all employees such as cleaning staff, housekeeping and administration staff. In addition, all inhabitants of an affiliated convent were included in the study, due to existing close patient interactions like pastoral care. It also covered a wide socioeconomic frame, and allowed for a good cross-section of gender, age and risk-groups.

This study population was felt to be representative for high risk individuals working in the health care system. A short-term evaluation of this prospective data was able to provide an overview about the evidence of local hygiene protocols.

J o u r n a l P r e -p r o o f All hospital employees and nuns between 18 and 90 years at the study center were given the opportunity to participate in this longitudinal monocentric trial. No pretesting was performed and the only exclusion criteria was any individual too unwell to participate at the outset of the study or lacking capacity to understand the informed consent.

The study center is a secondary care hospital located in the province of Schleswig-Holstein close to the border of the city of Hamburg. The hospital takes care of patients from 3 different regions: Schleswig-Holstein, Hamburg and Lower Saxony. Hamburg was one of the Hot-Spotregions during the SARS-CoV-2 pandemic in Germany. The hospital has 370 inpatient beds.

During the study period, 2 wards were dedicated solely as SARS-CoV-2 isolation wards, with a total capacity of 50 patients. The hospital has a usual critical care capacity for 20 patients who can be treated in the ICU (including mechanical ventilation). During the study period 18 confirmed COVID-19-patients were treated on the isolation wards.

A hospital-wide local hygiene standard was established at the beginning of the pandemic situation, prior to treating the first COVID-19-patient (Table 1) .

Beginning on March 25th, 2020 all staff members with direct patient care (PC) were to adhere to basic hygiene standards (such as wearing hospital clothing and surgical masks) for the duration of their shift. All non-medical staff members or staff members with no direct patient care (NPC), such as administration, pastoral care, logistics or facility management staff, were instructed to wear a face-mask only. In addition all employees working with COVID-19 suspected or confirmed patients must wear personal protective equipment (PPE) including filtering face piece-masks type 2 or 3 (FFP-2/FFP-3).

All study participants provided written and informed consent prior to enrolment.

All participants completed an initial questionnaire with items on demographics, general health and medication, working area and risk for potential SARS-CoV-2 exposure.

J o u r n a l P r e -p r o o f All study participants were asked for a weekly oropharyngeal swab (OPS) according to the recommendations of the Centers of Disease Control and Prevention (CDC).(Centers of Disease Control and Prevention) In addition, the participants could choose between either a weekly or monthly blood specimen collection as part of their participation. Participants were, however, not excluded if they were unable to provide the requested regular specimens. The sampling period began on April 14 th , 2020.

Medical employees were requested to provide their own OPS and had blood specimens performed from other trained medical colleagues. All non-medical employees had their OPS and blood specimen collected by study staff wearing PPE. (Corman et al. 2020) Study participants in which SARS-CoV-2 RNA was detected via PCR were informed immediately by the hospital occupational health provider with regards to their positive PCR result and a list of contact patients and contact personal was generated. Participants who tested positive for anti-SARS-CoV-2-IgG antibodies were also informed by the occupational health provider.

In the initial phase of the study period antibody-testing for anti-SARS-CoV-2 immunglobulin G (IgG) were performed using the recomWell SARS-CoV-2-IgG (Mikrogen Diagnostik, Germany) according to the manufacturer's instructions in blood serum samples. This enzyme-linked immunosorbent assay (ELISA) targets the SARS-CoV-2 nucleocapsid.

OPS were transported at room temperature within 24h after providing the sample. Initial testing was performed using cobas SARS-CoV-2 (Roche Diagnostics) for screening and control.

Because of capacity limitations ampliCube Coronavirus Panel (Mikrogen Diagnostics, Germany) for screening and RealStar SARS-CoV-2 RT-PCR Kit (Altona Diagnostics) as control were used in the initial phase as an alternative test kit.

In the second week of the study period a change of the laboratory was necessary due to local capacity. In the second laboratory OPS were tested using the same PCR test kits.

The antibody-testing was performed using the anti-SARS-CoV-2-ELISA (IgG) from Euroimmun (Lübeck, Germany) detecting the S1 domain of the SARS-CoV-2 spike-protein.

The follow-up after the presented study period was performed using the anti-SARS-CoV-2antibody assay from Abbott (Illinois, USA).

As this was a prospective observational study the analyses were mainly descriptive.

All variables were listed as means or medians with standard deviation. Categorical variables were arranged as numbers with percentages. The chi-square test was used to determine relationships between categorical variables and t-test was used to measure the probability of difference between two sets of data. A p<0.05 was considered statistically significant. The relation between antibody status and selected covariables was analysed with logistic regression. Odds ratios and 95% confidence Intervals were provided.

Statistical analyses were performed using IBM SPSS Statistics Version 25 (IBM Co., Armonk, NY, USA).

The study was approved by the Ethics Committee 038/20 I of the medical association Schleswig-Holstein, Germany and has been registered at the German Clinical Trial Register (DRKS00021270). The study was conducted in accordance with the Declaration of Helsinki.

In total 871 of 1081 (80.57%) employees at the study center were recruited to this study. There were no participants that met the exclusion criteria. All samples were provided voluntarily. The study period was 9 weeks, beginning on 14 April 2020.

There were 654 (75.09%) women and 217 (24.91%) men. The mean age was 40.0 (14,2) years. The largest professional groups represented in the study were nurses (n = 299), doctors J o u r n a l P r e -p r o o f (n = 149) and students or trainees (n = 71). Table 2 provides an overview of participants characteristics according to the two subgroups of PC or NPC.

Throughout the duration of the study period, 5329 OPS were collected and analyzed. In three participants (0.34%) SARS-CoV-2 RNA was detected via PCR during the course of the study period, one physician (PC), one nurse (PC) and one nun working in pastoral care (NPC). Two of the study participants with positive OPS reported mild symptoms such as coughing or sneezing, one of these persons reported being completely asymptomatic at the time of diagnosis and developed symptoms delayed to diagnosis. None was suspected for SARS-CoV-2. One of the three participants was hospitalized due to respiratory symptoms. None of the three individuals required intensive care. The transmission path could not be evaluated in any case. All detected infections resulted in an intensive screening program for possible contact patients or staff to prevent an outbreak in the hospital and its departments. Following this contact screening, none of the patients or staff members were subsequently tested positive for SARS-CoV-2. 

A total of 2136 blood specimens were collected and analyzed. The three seropositive individuals tested by the Euroimmun assay submitted a follow-up sample confirming the initial positive results ( Table 3) . For further statistical analysis equivocal positive results were mentioned as positive results.

The logistic regression analysis (Table 4 ) showed a significant relation of antibody status with age and body mass index, however not with sex and employment group. The likelihood for positive antibody test increased with increasing age (odds ratio for a 10 year difference 1.5) and decreased with increasing body mass index (odds ratio for an increase of 5 is 0.72).

To evaluate the antibody-assays an additional follow-up was performed and showed no positivity following the Abbott-and Euroimmun-assay in all individuals with a positive or equivocal initial Mikrogen-assay which handed in a follow-up blood specimen ( Table 5) . All individuals tested positive following the Euroimmun-assay were tested positive unsing all 3 assays within the follow-up.

Currently several studies have reported a higher transmission risk of SARS-CoV-2 for HCW. (Barrett et al. 2020; Gao et al. 2020; Li et al. 2020b; Liu et al. 2020; Reusken et al. 2020) The aim of this study was to examine the longitudinal prevalence of SARS-CoV-2 detected in employees of a healthcare facility affected by the COVID-19 outbreak from the beginning of the high active pandemic phase in a country with an overall low prevalence of SARS-CoV-2 and a highly developed healthcare system. Over the study period of 9 weeks, 3/871 (0.34%) participants had a positive OPS for SARS-CoV-2 and were placed in quarantine. No-one working on an isolation ward or treating COVID-19 patients tested positive within the period of this trial. This underlines the importance of the adherence to local and national hygiene guidelines to prevent a patient-to-staff infection. (Korth et al. 2020 ) A higher transmission rate J o u r n a l P r e -p r o o f could lead to a higher rate of SARS-CoV-2-positive OPS in healthcare workers as shown in different parts of the world. (Keeley et al. 2020; Kluytmans et al. 2020) The results presented in this study do not support this finding. Similarly, Barrett et al. could not confirm this in their work from the United States. (Barrett et al. 2020) This underlines the regional differences in the spread and the resulting response of hospitals 

The cumulative incidence of SARS-CoV-2 infection for the study period in the region of the hospital was 0.04%.(Kreis Stormarn) According to the data obtained in this study, the cumulative incidence in the hospital is almost ten times higher than outside the hospital. It is, however, important to bear in mind that the employees live in many different regions where the community incidence of SARS-CoV-2 may also be variable. This is a non measurable factor that may influence the results of this study. Furthermore, asymptomatic and not-tested individuals are not represented in the regional cumulative incidence.

In this study oral swabs were used to detect SARS-CoV-2-RNA by PCR, as was the recommendation of the Robert-Koch-Institute at the start of the study period(Robert-Koch-Institut) and as is still the recommendation of the CDC.(Centers of Disease Control and Prevention) Oral swabs were performed by medical trained participants following the instructions of the Robert-Koch-Institute(Robert-Koch-Institut) or else by specially trained staff J o u r n a l P r e -p r o o f members. Wehrhahn et al. showed in their report that performing swabs on your own is an acceptable alternative for obtaining OPS. (Wehrhahn et al. 2020 ) It was deemed appropriate in the study to use the dual form of specimen collection as this would prevent the risk of larger groups gathering.

In this study the over-all-seroprevalence of IgG antibodies against SARS-CoV-2 was 4.36%.

Using the Mikrogen-assay the seroprevalence was 4.13% compared to the Euroimmun-assay with a prevalence of 1.52%. Excluding equivocal results, the overall seroprevalence in this trial showed in their recently published data an early decrease of antibody titers in persons with mild symptoms of SARS-CoV-2. (Ibarrondo et al. 2020) Another possible explanation is that this can be caused by the performance characteristics of the different assays used during the study period.

To evaluate this potential causes we added another follow-up after the study period.

In this reevaluation we included in addition to the Mikrogen and the Euroimmun-assay the Abbott-assay. (Bryan et al. 2020 (Krüttgen et al. 2020) . At first glance, the differences in the specificities are very low, but it has quite considerable consequences if the pre-test probability is very low.

For example, the overall seroprevalence in the general German population account to approximately 1 %. (Fischer et al. 2020 ) With a seroprevalence of 1% and a specificity of 99%, the positive predictive value would be only 50%, meaning that half of the positive results would be false positive. This amount can be reduced using at least two different antibody assays. To evaluate this, further investigations, including additional serological assays and mid-and longterm-follow-up samples for all positive tested participants are required to finally determine the actual antibody status of these individuals. Unfortunately not all employees could be tested using both assays. This was caused by restricted testing capacities and the need of changing the laboratory during the trial.

The logistic regression showed a positive correlation between age and antibody-status. Filho et al. showed in their work from Brazil a negative correlation between age and antibody-status and argued this might be caused by younger people gathering in groups together. (Amorim Filho et al. 2020 ) The positive correlation found in our study could be caused by the fact that the included nuns live, work and commune together or could be an overestimation due to small number of cases. This correlation should be reevaluated in further seroprevalence studies.

Due to the low incidence of SARS-CoV-2 infections during the study period, an evaluation of potential risk factors for hospitalization such as medical history, smoking or obesity is not feasible. Further limitations of this study include the problem of performing and potential delay in transporting the samples. As medical staff were asked to perform the OPS on their own and handed them directly to the study center, a clear evaluation of the timepoint of sample collection remained impossible. It was impossible to obtain a daily report from study participants regarding possible COVID-19-symptoms. For all positive tested participants (either by PCR or antibodies), the exposure leading to an infection or to a seroconversion could not be identified. This problem was also discussed in the paper by Barrett et al.(Barrett et al. 2020 ) Contact tracing was more complicated as this study did not look at possible contacts outside the hospital work environment.

Due to capacity limitations it was necessary to change the laboratory cooperation during the study period. This change of laboratory also caused the change of test protocols and limits the longitudinal comparability.

Females and young people (in the group 18-30 years) are highly overrepresented in the presented data, especially in the PC-group. The study population of this secondary care hospital is therefore likely representative for other health care centers. The significant differences between both groups with regards to Previous Medical History might be attributable to the older median age within the NPC-group.

The small number of SARS-CoV-2-positive PCRs limited the statistical analysis. It could however reflect the fact, that health care workers are used to hygiene protocols and routinely equipped with adequate personal protection equipment. It might, however, indicate a lower prevalence of SARS-CoV-2 in the area of the study.

In summary despite the limitations of this study it provided a longitudinal epidemiological observation regarding infection rate amongst high risk health care workers.

This study provides the first longitudinal data for the spread of SARS-CoV-2 in a hospital taking care of COVID-19 patients. The low PCR-positive-incidence and seroprevalence during the study period underlines the potential effectiveness of the utilized local, regional and national protection plans. It reinforces the idea that personal protection measures play an important role in preventing of SARS-CoV-2 spread.

The results contradict the notion that hospitals carry a higher transmission risk for employees.

This study provides a longitudinal analysis encompassing different phases of lockdown and slow reopening. 

All patients with suspicion of COVID-19 infection or compatible symptoms are admitted directly to designated isolation wards All employees with direct patient care must wear surgical face masks and hospital issued clothing during the whole shift All employees with no direct patient care must wear face masks during the whole shift Hand hygiene must be performed according to the Guidelines provided by the Robert-Koch-

Access to the hospital is strictly regulated.

No training courses are held in the hospital. Tumor board or other meetings are held with limited number of members Access to the ICU is only allowed for registered staff members J o u r n a l P r e -p r o o f 

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

The study was approved by the Ethics Committee 038/20 I of the medical association Schleswig-Holstein, Germany and has been registered at the German Clinical Trial Register (DRKS00021270). The study was conducted in accordance with the Declaration of Helsinki.

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