Asymptomatic Healthcare Workers Research Articles

Nosocomial outbreak of δ (delta) variant SARS-CoV-2 on a liver transplant unit: A complex epidemiologic and genomic investigation

Background: In late September 2021, a cluster of patients with nosocomial COVID-19 was identified on a liver transplant unit at University of Nebraska Medical Center. Methods: The outbreak investigation included contact tracing via patient chart and employee health record reviews and serial prevalence testing for SARS-CoV-2 among potentially exposed patients and healthcare workers (HCWs). Routine admission and preprocedural screening for SARS-CoV-2 was performed, and involved patients had negative admission screening results with positive SARS-CoV-2 tests >5 days from admission. Mitigation strategies involved reinforcement of patient care and visitation procedures. Whole-genome sequencing of positive SARS-CoV-2 specimens was conducted. Results: The potential outbreak cluster included 6 patients in the same quadrant of the liver transplant unit, 1 visitor, and 11 healthcare workers (Fig. 1). Moreover, 4 patients had severe liver disease, including 2 with liver transplants. All HCWs and half of the patients had received 2 doses of mRNA vaccine, albeit >5 months from their second vaccination. Whole-genome sequencing confirmed patients 1–6 and HCWs 1–3 had related transmission of COVID-19. However, infections in HCWs 4–6, who worked in a transplant-related office setting without patient contact, were due to 2 separate introductions of SARS-CoV-2 unrelated to the hospital outbreak. Sequencing could not be performed on HCWs 7–11 due to low viral concentration in the original specimens or unavailable specimen. The SARS-CoV-2 δ (delta) variant (B.1.617.2) was identified in all sequenced samples. HCWs 8–10 were asymptomatic and had had contact with each other and had been involved with an intubation without proper PPE for SARS-CoV-2 on patient 6. HCW 8 had had contact with all 6 patients and HCW 9 had had contact with 5 patients. A clear index case could not be identified; however, we suspect that the index case was either visitor 1, who tested positive during patient 2’s admission, or an asymptomatic healthcare worker (HCWs 8–10). Conclusions: We identified a nosocomial outbreak of the SARS-CoV-2 δ (delta) variant in a solid-organ transplant unit including patients, a visitor, and vaccinated healthcare workers with multiple introductions of the virus. Further transmission was not detected after enhanced infection control measures were introduced, including universal masking and eye protection, closing patient doors, and enforcement of visitor masking policy. We describe the difficulties tracing SARS-CoV-2 transmission in the hospital setting, even with advanced sequencing techniques. This outbreak highlights the importance of booster vaccination and strict infection control practices, especially in the setting of the δ (delta) variant.Funding: NoneDisclosures: None

The role and relevance of asymptomatic healthcare worker testing in COVID-19 hospital outbreaks

Background: Many healthcare facilities have faced the decision of conducting point prevalence testing (PPT) of healthcare workers (HCW) during COVID-19 outbreaks. As a containment strategy, PPT can identify asymptomatic or presymptomatic cases for isolation. It is less clear how useful testing asymptomatic HCW is in understanding the spread and possible routes of transmission in an outbreak. This study investigated HCW cases identified through PPT during acute-care outbreaks in Fraser Health (FH), British Columbia, incorporating both epidemiological and whole-genome sequencing (WGS) data to determine their epidemiological source. Methods: This study was a retrospective review of cases associated with COVID-19 acute-care outbreaks in FH occurring between December 2020 and June 2021, when most of these infections were of the alpha and gamma lineages. All patients and HCWs with a positive COVID-19 test and epidemiologically linked to the outbreaks were included in the study. WGS results supported determination of epidemiological source for cases. The proportion of patient and HCW cases related to the outbreak was compared. All analyses were conducted using SAS version 4.3 software with the PROC GLM package. Results: Between December 2020 and June 2021, 49 acute-care COVID-19 outbreaks were declared. Point-prevalence testing of HCWs, in addition to routine patient PPT, was conducted in 28 outbreaks (57%), with 2,167 eligible HCWs (63%) tested. Testing identified 14 previously unknown HCW cases, representing 12.96% of all HCW cases epidemiologically linked to the outbreaks. None of these HCWs were determined to be the index case for their associated outbreak. There was no statistically significant difference between HCWs and patients regarding WGS failure rate, and all failed samples were removed from further analysis. Patients were 3.8 times as likely as HCWs to present as symptomatic when testing positive. HCWs were 2.2 times as likely as patients to have WGS results unrelated to the outbreak. Discussion: Although point-prevalence testing of HCW identified previously unknown cases, these cases were more likely than patients to be unrelated to the outbreak and therefore less useful in understanding the epidemiology of the outbreak. It is difficult to determine whether HCW PPT was effective at preventing transmission, especially with robust infection prevention measures already in place. Patients were more likely than HCWs to present as asymptomatic, however this may be due to the attribution of symptoms to other conditions. Conclusions: Point prevalence testing of HCWs during COVID-19 outbreaks may assist with preventing transmission but is less likely to contribute meaningful information to the investigation.Funding: NoneDisclosures: None

Saliva screening of health care workers for SARS-CoV-2 detection

Health care workers (HCWs) are at high risk for SARS-CoV-2. In addition, pre-symptomatic or asymptomatic transmission accounts for around half of the cases. Saliva testing is an option to detect SARS-CoV-2 infection. To determine the performance of saliva samples for screening, HCWs were tested for SARS-CoV-2 by RT-PCR. Those with a positive result in saliva were tested by nasopharyngeal swabbing for viral RNA detection and blood collection to search for the presence of specific antibodies. In September–October 2020, 100 HCWs were enrolled and followed up. Six subjects (6%) tested positive in saliva. Of them, 5/6 were positive in a subsequent nasopharyngeal swab and 4/6 developed signs and symptoms compatible with COVID-19. Among the latter, 3 seroconverted while asymptomatic HCWs remained seronegative. Saliva screening was helpful for identifying SARS-CoV-2 infection in HCWs. This screening permitted rapid personnel isolation avoiding further transmission of the virus in the hospital setting.

COVID-19: Healthcare Workers May Be at Greater Risk Outside Their Work Environment—A Retrospective Observational Study

BackgroundWith the availability of coronavirus disease 2019 (COVID-19) vaccine, concerns have been raised regarding pre-vaccination seroprevalence in healthcare workers (HCW). This study examines the seroprevalence of HCW at an Israeli tertiary medical center before first BNT162b2 vaccination.MethodsThis was a retrospective observational study. Before vaccination, HCW at our center were offered serological testing. Data on their epidemiological, workplace, and quarantine history were collected. The SARS-CoV-2 IgG assay was performed pre-vaccination.ResultsA total of 4,519 (82.5%) of the HCW were tested. Of these, 210 were seropositive; 101 had no known history of COVID-19. Of the 101 asymptomatic HCW, only 3 (3%) had worked at COVID-19 departments, and 70 (69.3%) had not been previously quarantined. Positive serology was similarly distributed across age groups, and about 40% had no children. Nearly half of the HCW tested were administrative and service staff. Overall, seropositive tests were associated with having no children (OR 1.42, 95% CI 1.06–1.89; P=0.0218), history of having been quarantined without proof of disease (OR 6.04, 95% CI 4.55–8.01; P<0.001), and Arab ethnicity (OR 3.36, 95% CI 2.54–4.43; P<0.001). Seropositivity was also more prevalent in members of the administration compared to other sectors, medical and paramedical, who are exposed to patients in their daily work (OR 1.365, 95% CI 1.02–1.82; P=0.04).ConclusionsThe low percentage of asymptomatic COVID-19 among our HCW may reflect the high compliance to personal protective equipment use despite treating hundreds of COVID-19 patients. The relatively high number of childless seropositive HCW could reflect misconceptions regarding children as a main source of infection, leading to carelessness regarding the need for appropriate out-of-hospital protection.

Pooled-Testing for SARS-CoV-2 Reverse Transcription Polymerase Chain Reaction (RT-PCR) in asymptomatic healthcare workers in EL-Raghy isolation COVID-19 hospital, Assiut University

COVID-19 pandemic is a substantial challenge for healthcare systems. Severe acute respiratory syndrome coronavirus (SARS-CoV-2) reverse transcription-polymerase chain reaction (RT-PCR) tests are considered the gold standard technique for diagnosis of symptomatic and asymptomatic infectious viral carriers and for screening special or at-risk populations. The pooled testing procedure is commonly used to reduce the cost of screening a large number of individuals for infectious diseases. This work was conducted to verify the accuracy of the standard SARS COV-2 RT- real-time PCR kit for detecting a single positive sample in a pool of negative samples. Kit verification using negative and positive samples was performed for the selection of the target pool sizes. RNA extracts from 443 healthcare workers, after 15 days' rotation in EL-Raghy Isolation COVID-19 Hospital, Assiut University during the first outbreak of COVID-19 pandemic (the period from June to September 2020) were obtained and tested. Sixty-three different pool sizes (2, 3, 4, 5, 6, 7, 8, 9, and 10) were tested for the presence of SARS-CoV-2 using RT-qPCR. Of these, 53 pools (84.1%) were negatives and 10 pools (15.9 %) tested positive. The individual number of SARS- COV 2 RT-PCR tests used in different pool sizes was 40 tests. The total number of SARS- COV 2 RT-PCR test used in this study was 110 tests instead of 443 tests which reflect a decrease in cost up to 75.16%. In conclusion, the suggested pooling strategy can reduce testing loads which enable substantial savings in reagent costs, technical burden, and time to generate laboratory results.

Rapid antigen test during a COVID-19 outbreak in a private hospital in Hong Kong.

In response to two nosocomial clusters of coronavirus disease 2019 (COVID-19) in our hospital, we adopted a series of strict infection control measures, including regular rapid antigen test (RAT) screening for high-risk patients, visitors, and healthcare workers. We evaluated the diagnostic performance of a locally developed RAT, the INDICAID COVID-19 Rapid Antigen Test (Phase Scientific, Hong Kong), using respiratory samples from both symptomatic and asymptomatic individuals. Real-time reverse-transcription polymerase chain reaction (rRT-PCR)-confirmed deep throat saliva (DTS) and pooled nasopharyngeal swab and throat swab (NPS/TS) samples collected from 1 November to 30 November 2020 were tested by INDICAID. Screening RATs were performed on asymptomatic healthcare workers during a 16-week period (1 December 2020 to 22 March 2021). In total, 20 rRT-PCR-confirmed samples (16 DTS, four pooled NPS/TS) were available for RAT. Using the original sample, RAT results were positive in 17/20 samples, indicating 85% sensitivity (95% confidence interval [CI]=62.11%-96.79%). Negative RAT results were associated with higher cycle threshold (Ct) values. For samples with Ct values <25, the sensitivity was 100%. Of the 49 801 RATs collected from healthcare workers, 33 false positives and one rRT-PCR-confirmed case were detected. The overall specificity was 99.93% (95% CI=99.91%-99.95%). The positive and negative predictive values were 2.94% (95% CI=2.11%-4.09%) and 100%, respectively. The INDICAID COVID-19 RAT demonstrated good sensitivity for specimens with high viral loads and satisfactory specificity for low-risk, asymptomatic healthcare workers.

Real World Performance of SARS-CoV-2 Antigen Rapid Diagnostic Tests in Various Clinical Settings.

To assess the validity of Antigen rapid diagnostic tests (Ag-RDT) for SARS-CoV-2 as decision support tool in various hospital-based clinical settings. Retrospective cohort study among symptomatic and asymptomatic patients and Healthcare workers (HCW). A large tertiary teaching medical center serving as a major COVID-19 hospitalizing facility. Ag-RDTs' performance was assessed in three clinical settings: 1. Symptomatic patients and HCW presenting at the Emergency Departments 2. Asymptomatic patients screened upon hospitalization 3. HCW of all sectors tested at the HCW clinic following exposure. We obtained 5172 samples from 4595 individuals, who had both Ag-RDT and quantitative real-time PCR (qRT-PCR) results available. Of these, 485 samples were positive by qRT-PCR. The positive percent agreement (PPA) of Ag-RDT was greater for lower cycle threshold (Ct) values, reaching 93% in cases where Ct-value was <25 and 85% where Ct-value was <30. PPA was similar between symptomatic and asymptomatic individuals. We observed a significant correlation between Ct-value and time from infection onset (p<0.001). Ag-RDT are highly sensitive to the infectious stage of COVID-19 manifested by either high viral load (lower Ct) or proximity to infection, whether patient is symptomatic or asymptomatic. Thus, this simple-to-use and inexpensive detection method can be used as a decision support tool in various in-hospital clinical settings, assisting patient flow and maintaining sufficient hospital staffing.

Comparative Analysis of Circulating Levels of SARS-CoV-2 Antibodies and Inflammatory Mediators in Healthcare Workers and COVID-19 Patients.

Advances in knowledge of the pathophysiology of COVID-19 have been acquired; however, the host factors that could explain the mild and severe forms of the disease are not fully understood. Thus, we proposed to evaluate anti-SARS-CoV-2 antibodies and the inflammatory response of different groups of individuals, including healthcare workers (HCW), sick and dead COVID-19 patients and also recovered patients to contribute to this knowledge gap. Our objective is to relate the clinical evolution of these individuals with the level of detection and functionality of specific antibodies and with the production of inflammatory mediators. As main findings, IgA and IgG anti-SARS-CoV-2 were detected in asymptomatic HCW. IFN-γ and TNF-α levels were higher in symptomatic HCWs than patients with COVID-19 and those who died. Patients who died had higher levels of IL-6, IL-10, and CCL2/MCP-1. We found an imbalance between antiviral and pro-inflammatory mediators in the groups, in which IFN-γ and TNF-α seem to be more associated with protection and IL-6 and CCL2/MCP-1 with pathology. Our work is pioneering the Brazilian population and corroborates data from people from other countries.

Protection against SARS-CoV-2 after Covid-19 Vaccination and Previous Infection

BackgroundThe duration and effectiveness of immunity from infection with and vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are relevant to pandemic policy interventions, including the timing of vaccine boosters.MethodsWe investigated the duration and effectiveness of immunity in a prospective cohort of asymptomatic health care workers in the United Kingdom who underwent routine polymerase-chain-reaction (PCR) testing. Vaccine effectiveness (≤10 months after the first dose of vaccine) and infection-acquired immunity were assessed by comparing the time to PCR-confirmed infection in vaccinated persons with that in unvaccinated persons, stratified according to previous infection status. We used a Cox regression model with adjustment for previous SARS-CoV-2 infection status, vaccine type and dosing interval, demographic characteristics, and workplace exposure to SARS-CoV-2.ResultsOf 35,768 participants, 27% (9488) had a previous SARS-CoV-2 infection. Vaccine coverage was high: 95% of the participants had received two doses (78% had received BNT162b2 vaccine [Pfizer–BioNTech] with a long interval between doses, 9% BNT162b2 vaccine with a short interval between doses, and 8% ChAdOx1 nCoV-19 vaccine [AstraZeneca]). Between December 7, 2020, and September 21, 2021, a total of 2747 primary infections and 210 reinfections were observed. Among previously uninfected participants who received long-interval BNT162b2 vaccine, adjusted vaccine effectiveness decreased from 85% (95% confidence interval [CI], 72 to 92) 14 to 73 days after the second dose to 51% (95% CI, 22 to 69) at a median of 201 days (interquartile range, 197 to 205) after the second dose; this effectiveness did not differ significantly between the long-interval and short-interval BNT162b2 vaccine recipients. At 14 to 73 days after the second dose, adjusted vaccine effectiveness among ChAdOx1 nCoV-19 vaccine recipients was 58% (95% CI, 23 to 77) — considerably lower than that among BNT162b2 vaccine recipients. Infection-acquired immunity waned after 1 year in unvaccinated participants but remained consistently higher than 90% in those who were subsequently vaccinated, even in persons infected more than 18 months previously.ConclusionsTwo doses of BNT162b2 vaccine were associated with high short-term protection against SARS-CoV-2 infection; this protection waned considerably after 6 months. Infection-acquired immunity boosted with vaccination remained high more than 1 year after infection. (Funded by the U.K. Health Security Agency and others; ISRCTN Registry number, ISRCTN11041050.)

ESCMID guidelines on testing for SARS-CoV-2 in asymptomatic individuals to prevent transmission in the health care setting

ScopeThis guideline addresses the indications for direct testing of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in asymptomatic individuals in health care facilities, with the aim to prevent SARS-CoV-2 transmissions in these settings. The benefit of testing asymptomatic individuals to create a safe environment for patients and health care workers must be weighed against potential unintended consequences, including delaying necessary treatments owing to false positive results and lower quality of care owing to strict isolation measures. MethodsA total of nine PICOs (population, intervention, comparison, outcome) on the topic of testing asymptomatic individuals was selected by the panel members. Subsequently, a literature search for existing guidelines and systematic reviews was performed on PubMed, Epistemonikos, and RecMap using relevant filters available in each database. Data on article/recommendation type, setting, target population, intervention, and quality of the evidence were extracted. Credibility of the systematic reviews was evaluated using the AMSTAR tool, and level of agreement with available recommendation was evaluated with the AGREE II score. Because the evidence available from systematic reviews was deemed insufficiently updated to formulate relevant recommendations, an additional search targeting relevant guidance documents from major public health institutions and original studies was performed. Provisional recommendations were discussed via web conferences until agreement was reached, and final recommendations were formulated according to the GRADE approach. RecommendationsRecommendations were formulated regarding systematic testing in asymptomatic individuals upon admission to a health care setting, during hospital stay, before elective procedures, and before scheduled nonsurgical procedures. Moreover, recommendations regarding testing of asymptomatic visitors, personal caregivers, and health care workers in health care facilities were presented. Recommendations also were given on contact tracing in asymptomatic patients or health care workers and the possibility of a negative screening test to shorten the quarantine period. Furthermore, if applicable, recommendations were specified to transmission rate and vaccination coverage.

SARS-COV-2 Screening of Health Care Workers in Brunei Darussalam.

Health care workers (HCWs) are at high risk of COVID-19 infection; therefore, screening is recommended for early detection and management to break the chain of transmission. Globally, multiple strategies have been utilized for the screening of HCWs. This article reports and evaluates an active surveillance and screening strategy for severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) among HCWs following work or nonwork exposures in Brunei Darussalam to prevent health care-associated COVID-19 transmission. In March 2020, the Ministry of Health through the Occupational Health Division adopted an active screening strategy for symptomatic and asymptomatic HCWs, which involved symptom screening, risk assessment, SARS-COV-2 testing, and management following work/nonwork exposure and recent overseas travel, and those with influenza-like illness (ILI) symptoms. Screening frequency was based on the HCWs' symptoms and exposure, with the intent to evaluate all possible sources of exposure. As of December 31, 2020, 821 HCWs were screened, of which 632 (77%) had ILI symptoms and 14 (1.7%) had high-risk occupational exposure. Reverse transcription polymerase chain reaction (RT-PCR) swab testing was carried out on 577 (70.3%) HCWs, with the highest proportion of swabs done on doctors (85.1%; p < .01) due to their workplace exposure (34.3%) and overseas travel (38.7%). By July 2021, Brunei Darussalam had recorded zero cases of COVID-19 among HCWs from occupational exposure. Our strategy of active screening for SARS-COV-2 RT-PCR testing since early in the outbreak has proven to be successful, in combination with infection control practices and public health measures, in the prevention of occupational transmission, thereby facilitating early return to work for HCWs with low-risk exposure and without symptoms.

Coronavirus Disease-19 Testing Strategies for Patients and Health Care Workers to Improve Workplace Safety.

Tests to detect active viral infection and related immune response in the staff and patients attending health care facilities effectively identified positive cases presenting with or without symptoms of coronavirus disease (COVID)-19. Subsequent home isolation of these contagious cases helped curb the chance of the spread of infection at the workplace. Furthermore, serologic tests conducted postvaccination facilitated the detection of individuals with poor immune response following active immunization that would likely require further safety measures to protect themselves from contracting the infection in health care facilities.

Longitudinal Monitoring of Seroconversion Status in SARS-CoV-2 RT-PCR Positive Healthcare Workers

The impact of the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome 2 (SARS-CoV-2) still continues. The duration of the immune response in individuals recovering from COVID-19 and its protection against future SARS-CoV-2 infection are not fully understood. This study aimed to longitudinally evaluate anti-SARS-CoV-2 seroconversion status in healthcare workers with positive SARS-CoV-2 Real-time reverse transcription polymerase chain reaction (rRT-PCR), test in Mersin University Hospital. A total of 68 healthcare workers with positive SARS-CoV-2 rRT-PCR test between 19 April and 27 November 2020 were included in the study. Blood samples were collected from healthcare workers for SARS-CoV-2 antibody testing in the 1st, 3rd and 5th months following PCR positivity. Healthcare workers were classified as symptomatic, asymptomatic and reinfected according to their clinical findings, and rRT-PCR cycle thresholds (Ct) were recorded. Elecsys Anti-SARS-CoV-2 (Roche Diagnostics, Germany) kit was used for antibody testing. Of the 68 healthcare workers; 46 were classified as symptomatic, 15 as asymptomatic, and seven as reinfected. Twenty-seven (39.7%) of the healthcare workers were male and 41 (60.3%) were female, and the mean age was 36.4 ± 9.04. Seroconversion was detected in 45 (66.2%) of 68 healthcare workers in the study, and only one person had sero-negative result at the end of the 5th month. While seroconversion was detected in 78.3% (n= 36/46) of symptomatic healthcare workers, it was observed in 26.7% (n= 4/15) of the asymptomatic healthcare workers. Seroconversion was detected in only one of the seven reinfected healthcare workers after primary infection. After reinfection, seroconversion was observed in five of seven reinfected healthcare workers. Antibody response was not detected in two of them after both infections. According to the rRT-PCR Ct values; the median of Ct value was found significantly lower in healthcare workers with seroconversion (23.26, IQR= 18.45-27.30), than the ones without seroconversion (36.20, IQR= 33.09-37.56) (p< 0.001). In those who had reinfection, the mean Ct value (31.77 ± 6.62) detected during the primary infection period was statistically higher than the Ct value (22.44 ± 5.54) detected during reinfection (p= 0.008). The most frequently recorded symptoms in healthcare workers were myalgia (57.3%), fatigue (51.5%), headache (51.5%) followed by sore throat (36.7%), fever (33.8%), cough (27.9%), diarrhea (23.5%) and dyspnea (16.2%). In addition, fever (52%) and fatigue (80.6%) were found to be significantly higher in seroconversion-positive healthcare workers than in those without seroconversion (p= 0.028; p= 0.005, respectively). As a result, a higher rate of antibody response was detected in healthcare workers who had symptomatic infection than those who were asymptomatic. It has been observed that patients with asymptomatic primary infection and without antibody response were more susceptible to reinfection. In addition, it was observed that the probability of immune response increased when the viral load increased (Ct value decreased) in symptomatic infections. Although these findings provide important information about the short-term seroconversion status of healthcare personnel; longer-term and larger-scale studies are needed to evaluate the long-term effectiveness of seroconversion and to better understand the effectiveness of the immune response developed after SARS-CoV-2 vaccine administrations.

Optimal strategies to screen health care workers for COVID-19 in the US: a cost-effectiveness analysis

BackgroundTransmission of SARS-CoV-2 in health care facilities poses a challenge against pandemic control. Health care workers (HCWs) have frequent and high-risk interactions with COVID-19 patients. We undertook a cost-effectiveness analysis to determine optimal testing strategies for screening HCWs to inform strategic decision-making in health care settings.MethodsWe modeled the number of new infections, quality-adjusted life years lost, and net costs related to six testing strategies including no test. We applied our model to four strata of HCWs, defined by the presence and timing of symptoms. We conducted sensitivity analyses to account for uncertainty in inputs.ResultsWhen screening recently symptomatic HCWs, conducting only a PCR test is preferable; it saves costs and improves health outcomes in the first week post-symptom onset, and costs $83,000 per quality-adjusted life year gained in the second week post-symptom onset. When screening HCWs in the late clinical disease stage, none of the testing approaches is cost-effective and thus no testing is preferable, yielding $11 and 0.003 new infections per 10 HCWs. For screening asymptomatic HCWs, antigen testing is preferable to PCR testing due to its lower cost.ConclusionsBoth PCR and antigen testing are beneficial strategies to identify infected HCWs and reduce transmission of SARS-CoV-2 in health care settings. IgG tests’ value depends on test timing and immunity characteristics, however it is not cost-effective in a low prevalence setting. As the context of the pandemic evolves, our study provides insight to health-care decision makers to keep the health care workforce safe and transmissions low.

Antibody responses after two doses of CoronaVac of the participants with or without the diagnosis of COVID-19

BackgroundCoronaVac, an inactivated whole-virion vaccine against COVID-19, has been shown to be safe with acceptable antibody responses by various clinical trials.AimsThe objective was to investigate the post-vaccination antibody levels of both symptomatic and asymptomatic healthcare workers with or without the diagnosis of COVID-19 in an emergency department (ED) of a hospital serving as a pandemic hospital.MethodsThis single-centred, prospective study was conducted on 86 participants who were working as nurse or doctor in the ED. The volunteers were older than 18 years and either positive or negative for either computed tomography (CT), real-time reverse transcription polymerase chain reaction (qRT-PCR), or both. Thirty days after the second dose of CoronaVac (3 µg), the antibody levels were chemiluminescent microparticle immunoassay.ResultsMean age of all participants were 33.1 ± 9.1 years. The antibody levels in the qRT-PCR( +) and CT( +) groups were significantly higher than the qRT-PCR( −) and CT( −) groups, respectively (p < 0.05). In the CT( +)/qRT-PCR( +) group, the antibody level was significantly higher than the CT( −)/qRT-PCR( −) and CT( −)/qRT-PCR( +) or CT( +)/qRT-PCR( −) group (p < 0.05). On the other hand, antibody levels in the hospitalized group were significantly higher than in the non-hospitalized group (p < 0.05). A significant positive correlation was observed between the time elapsed after vaccination and antibody levels of the participants (r = 0.343; p = 0.000).ConclusionIn conclusion, antibody responses of recovered patients COVID-19 diagnosed by both CT and qRT-PCR were much robust than the patients diagnosed by either one of the techniques or undiagnosed/disease-free participants suggesting that severity of the disease likely contributes to the antibody responses after vaccination with CoronaVac.

Severe acute respiratory syndrome coronavirus 2 infection among healthcare workers in a tertiary public hospital in Curitiba, Brazil.

ABSTRACTBACKGROUND: We aimed to describe the clinical characteristics of coronavirus disease 2019 (COVID-19) among healthcare workers (HCWs) in Curitiba, Brazil. METHODS: Upper respiratory samples from 1077 HCWs were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using reverse transcription polymerase chain reaction from June 16, 2020 to December 9, 2020. RESULTS: Overall, 32.7% of HCWs were infected. The positivity rates in symptomatic and asymptomatic HCWs were 39.2% and 15.9%, respectively. Hospital departments categorized as high-risk for exposure had the highest number of infected HCWs. CONCLUSIONS: Early diagnosis and isolation of infected HCWs remain key in controlling SARS-CoV-2 transmission because HCWs in close contact with COVID-19 patients are more likely to be infected than those who are not.

Coronavirus disease 2019 (COVID-19) polymerase chain reaction (PCR) screening of asymptomatic healthcare workers in a low-prevalence setting: A single-center UK cohort study.

In this cohort study of UK healthcare workers, we evaluated the use of fortnightly polymerase chain reaction (PCR) screening to facilitate the safe resumption of elective surgery in a low-prevalence setting. We found that adherence to serial testing was poor, and the resource required to identify 1 asymptomatic case was substantial.

Asymptomatic SARS-COV-2 carriage and sero-positivity in high risk contacts of COVID-19 cases’

PurposeIdentifying asymptomatic SARS-COV-2 carriage is one of the crucial factors in controlling the COVID 19 pandemic. The relationship between the asymptomatic viral carriage and the rate of seroconversion needs better understanding. The present study was conducted to identify the asymptomatic COVID-19 infection and seropositivity in high-risk contacts in the southern district of Delhi, India. MethodsFollowing the screening of 6961 subjects, a total of 407 asymptomatic high-risk subjects were selected. Demographic data, socioeconomic status, and history of COVID-19 related symptoms in the last 4 months were recorded. Blood samples and Nasopharyngeal/oropharyngeal swabs were collected for the detection of SARS-COV-2 RNA and anti-SARS-COV-2 antibodies. Results55 asymptomatic high-risk subjects (13.5%) tested positive for SARS-COV-2 infection and among them, 70.9% remained asymptomatic throughout their course of infection. The seropositivity among the subjects was 28.9% (n ​= ​118) and was found significantly higher among lower-middle socioeconomic strata (p ​= ​0.01). The antibody levels were significantly higher (p ​= ​0.033) in individuals with a previous history of COVID-19 like symptoms as compared to the subjects, who had no such history. Asymptomatic healthcare workers showed a significantly increased rate of SARS-COV-2 infection (p ​= ​0.004) and seropositivity (p ​= ​0.005) as compared to the non-healthcare workers. Subjects, who were exposed to infection at their workplace (non-hospital setting) had the least RT-PCR positivity rate (p ​= ​0.03). ConclusionsA large proportion of SARS-COV-2 infection remains completely asymptomatic. The rate of asymptomatic carriage and seropositivity is significantly higher in healthcare workers as compared to the general population. The level of SARS-COV-2 antibodies is directly related to the appearance of symptoms. These observations may contribute to redefining COVID 19 screening, infection control, and professional health practice strategies.

Potential SARS-CoV-2 infectiousness among asymptomatic healthcare workers.

A majority of SARS-CoV-2 infections are transmitted from a minority of infected subjects, some of which may be symptomatic or pre-symptomatic. We aimed to quantify potential infectiousness among asymptomatic healthcare workers (HCWs) in relation to prior or later symptomatic disease. We previously (at the onset of the SARS-CoV-2 epidemic) performed a cohort study of SARS-CoV-2 infections among 27,000 healthcare workers (HCWs) at work in the capital region of Sweden. We performed both SARS-CoV-2 RT-PCR and serology. Furthermore, the cohort was comprehensively followed for sick leave, both before and after sampling. In the present report, we used the cohort database to quantify potential infectiousness among HCWs at work. Those who had sick leave either before or after sampling were classified as post-symptomatic or pre-symptomatic, whereas the virus-positive subjects with no sick leave were considered asymptomatic. About 0.2% (19/9449) of HCW at work were potentially infectious and pre-symptomatic (later had disease) and 0.17% (16/9449) were potentially infectious and asymptomatic (never had sick leave either before nor after sampling). Thus, 33% and 28% of all the 57 potentially infectious subjects were pre-symptomatic or asymptomatic, respectively. When a questionnaire was administered to HCWs with past infection, only 10,5% of HCWs had had no indication at all of having had SARS-CoV-2 infection ("truly asymptomatic"). Our findings provide a unique quantification of the different groups of asymptomatic, potentially infectious HCWs.

400. Impact of SARS-CoV-2 Test-based Strategy to Reduce Quarantine Days Among Asymptomatic Healthcare Workers After Household Exposure

BackgroundAppropriate staffing is essential to provide safe patient care. During the COVID-19 pandemic, healthcare workers (HCWs) are missing work days due to illness or high-risk exposure (HRE) to an infected person. To avoid staffing shortages, we implemented a SARS-CoV-2 test-based strategy among asymptomatic HCWs after HRE to facilitate early return to work.MethodsIn July 2020, our institution implemented a SARS-CoV-2 RT-PCR test-based strategy among HCWs within 7 days of HRE. HCWs were defined as any paid or unpaid persons directly or indirectly involved in patient care. HRE was defined as close contact < 6 feet with an infected household member without use of mask and lasting for ≥ 15 minutes. Contact with a patient or coworker was not considered high-risk due to universal masking and eye protection use. HCWs underwent SARS-CoV-2 RT PCR testing of a nasopharyngeal swab at least once (1-2 days post-exposure) or twice (5-7 days post-exposure). HCWs with symptoms at baseline were excluded. HCWs who were asymptomatic during evaluation were considered as truly asymptomatic (TA). Saved work-days (SWD) were calculated based on number of days saved due to testing strategy compared to the Centers for Disease Control and Prevention’s recommended 14-day quarantine. HCWs were allowed to return to work within 7 days of HRE if they tested negative, or after completing 10-day isolation period ± improvement in symptoms from symptom onset if they tested positive.ResultsBetween 07/01/2020 to 12/31/2020, 450 unique asymptomatic HCWs underwent SARS-CoV-2 testing. Of those, 84% were women and median age was 36 years, 347 tested negative and 103 tested positive. Of those positives, 33% of HCWs tested positive on day 2 after HRE with 141 SWDs (average 2 days/person). Only 37% were TA positives. Of those negatives, 94% were TA SARS-CoV-2 negative with 2620 SWDs (average 7.5 days/person). There were no healthcare outbreaks related to HCWs allowed to return to work following this strategy. Asymptomatic healthcare workers commonly tested positive for SARS-CoV-2 on day 2 from household exposure compared to other daysConclusionTest-based strategy among asymptomatic HCWs with HRE reduced loss of workdays and helped limit staffing shortages. Majority of positive HCWs developed symptoms after positive SARS-CoV-2 testing, which may support allowing most fully vaccinated HCWs with no COVID-like symptoms to continue to work unless symptomatic.Disclosures All Authors: No reported disclosures