Rate Of Asymptomatic Infection Research Articles

Perinatal COVID-19.

Perinatal COVID-19.

Incidence Rates, Household Infection Risk, and Clinical Characteristics of SARS-CoV-2 Infection Among Children and Adults in Utah and New York City, New York

Data about the risk of SARS-CoV-2 infection among children compared with adults are needed to inform COVID-19 risk communication and prevention strategies, including COVID-19 vaccination policies for children. To compare incidence rates and clinical characteristics of SARS-CoV-2 infection among adults and children and estimated household infection risks within a prospective household cohort. Households with at least 1 child aged 0 to 17 years in selected counties in Utah and New York City, New York, were eligible for enrollment. From September 2020 through April 2021, participants self-collected midturbinate nasal swabs for reverse transcription-polymerase chain reaction testing for SARS-CoV-2 and responded to symptom questionnaires each week. Participants also self-collected additional respiratory specimens with onset of COVID-19-like illness. For children unable to self-collect respiratory specimens, an adult caregiver collected the specimens. The primary outcome was incident cases of any SARS-CoV-2 infection, including asymptomatic and symptomatic infections. Additional measures were the asymptomatic fraction of infection calculated by dividing incidence rates of asymptomatic infection by rates of any infection, clinical characteristics of infection, and household infection risks. Primary outcomes were compared by participant age group. A total of 1236 participants in 310 households participated in surveillance, including 176 participants (14%) who were aged 0 to 4 years, 313 (25%) aged 5 to 11 years, 163 (13%) aged 12 to 17 years, and 584 (47%) 18 years or older. Overall incidence rates of SARS-CoV-2 infection were 3.8 (95% CI, 2.4-5.9) and 7.7 (95% CI, 4.1-14.5) per 1000 person-weeks among the Utah and New York City cohorts, respectively. Site-adjusted incidence rates per 1000 person-weeks were similar by age group: 6.3 (95% CI, 3.6-11.0) for children 0 to 4 years, 4.4 (95% CI, 2.5-7.5) for children 5 to 11 years, 6.0 (95% CI, 3.0-11.7) for children 12 to 17 years, and 5.1 (95% CI, 3.3-7.8) for adults (≥18 years). The asymptomatic fractions of infection by age group were 52%, 50%, 45%, and 12% among individuals aged 0 to 4 years, 5 to 11 years, 12 to 17 years, and 18 years or older, respectively. Among 40 households with 1 or more SARS-CoV-2 infections, the mean risk of SARS-CoV-2 infection among all enrolled household members was 52% (range, 11%-100%), with higher risks in New York City compared with Utah (80% [95% CI, 64%-91%] vs 44% [95% CI, 36%-53%]; P < .001). In this study, children had similar incidence rates of SARS-CoV-2 infection compared with adults, but a larger proportion of infections among children were asymptomatic.

S553 Reevaluating the Need for Pre-Endoscopic COVID-19 Testing: A Single Center Retrospective Study

Introduction: On May 21st, the American Gastroenterological Association (AGA) updated its July 2020 Covid-19 testing guidelines, recommending against routine pre-endoscopic procedure Covid-19 testing. Prior, the community standard of care was to perform pre-endoscopy Covid-19 testing because endoscopic procedures posed a level-1 Covid-19 exposure risk to healthcare providers (HCPs). Pre-endoscopy Covid-19 testing unnecessarily consumes healthcare resources, since asymptomatic infection rates are low and the majority of HCPs are vaccinated against Covid-19. Here, we present the pre-endoscopy Covid-19 testing data from a New Jersey urban community gastroenterology clinic to evaluate the AGA recommendation. Methods: Retrospective analysis of all pre-endoscopy Covid-19 tests was performed. Between 5/20/2020 and 6/18/2021, pre-endoscopy Covid-19 testing was performed on 1097 patients. Patients were first administered a standard Covid-19 symptom screening questionnaire one week prior to endoscopy. Next, the HCP performed a nasopharyngeal specimen (NP) collection within 4 days of the endoscopic procedure, following the CDC clinical guidelines. Same day Covid-19 testing was performed on the NP specimen using the Thermo Fisher TaqMan 2019-nCoV Assay Kit v1, TaqMan 2019-nCoV Control Kit v1Test, TaqPath Covid-19 Combo Kit, or Panther Fusion® SARS-CoV-2 Assay Kit by real-time (RT) PCR. When the NP specimen was insufficient (ie. equivocal PCR amplification, missing specimen, contamination), pre-endoscopy Covid-19 testing protocol was repeated. Results: 0 study participants reported Covid-19 symptoms through the symptom screening questionnaire. Of the 1097 pre-endoscopy Covid-19 tests performed, Covid-19 was detected in 21 samples and was not detected in the remaining 1076 samples. An infection positivity rate of 1.91% was observed. The range of study participant age was 18 to 88. The median age was 54, and the mean age was 52.1. 55% of study participants were female. The race distribution was as follows: 42% White, 23% Hispanic, 18% Asian, 10% Black, 7% other. Conclusion: Study results support the AGA’s recommendation, demonstrating that pre-endoscopic procedure Covid-19 testing is unnecessary due to low asymptomatic infection rates. However, emergent Covid-19 variants may pose new risks to HCPs and vaccinated individuals. The GI community must continue to monitor infection rates, and reevaluate Covid-19 testing guidelines as needed.

S1278 Asymptomatic Pediatric COVID-19 Positive Patients Captured Through Pre-operative Screening Program for Ambulatory Surgeries at a Tertiary Care Hospital

Introduction: Our hospital implemented universal pre-operative COVID-19 screening in April 2020 to reduce risk of transmission to caregivers as well to avert a potential anesthetic risk in COVID positive patients. The aim of this project was to determine the prevalence of asymptomatic COVID-19 infection among pediatric patients undergoing ambulatory procedures and surgeries, overall and for Pediatric Gastroenterology (GI) cases specifically. Methods: A retrospective chart review identified pediatric patients (≤21 years) who underwent ambulatory pre-operative COVID-19 testing between April 1, 2020-March 31, 2021. Demographic and health-related data was collected to identify asymptomatic COVID-19 positive patients scheduled for GI procedures and other ambulatory surgeries. We compared the proportion of patients who tested positive by age group, co-morbid condition, and surgical specialty. We also compared pediatric case rates to Ohio case rates. The study was IRB approved. Results: 4,663 asymptomatic pediatric patients underwent pre-operative COVID-19 testing by PCR and 81 patients were identified as positive (1.73%). In COVID-19 positive patients, 56% were male and 44% were female. Mean age was 12 years and patients 13-18 years were the age group with the highest fraction of positive tests (35%). 11% of patients screened were undergoing a GI-related procedure with a positivity rate of 1.3%. The peak in asymptomatic positives across all procedures occurred in November 2020 (30%), which preceded the peak in COVID-19 cases in Ohio by several weeks. Most prevalent co-morbid condition was asthma (15%) and 8% had inflammatory bowel disease. 5 patients were undergoing chemotherapy and none were on biologic therapy. 94% of cases were deferred. 25% of cases that proceeded required post-operative admission. Conclusion: Asymptomatic COVID-19 positive patients were identified before 1.73% of pediatric ambulatory procedures and before 1.3% of GI procedures. These case rates were higher than the concurrent adult case rate at our institution. The higher rate of asymptomatic COVID-19 infection in pre-operative pediatric ambulatory patients may reflect the milder disease in this age group. The peak in pediatric asymptomatic case positivity seemed to predict the subsequent peak case rate in the state of Ohio by a few weeks. As the pandemic continues with a large percentage of pediatric patients unvaccinated, pre-operative COVID-19 testing has important implications for pediatric GI and other ambulatory procedures.

A Multiplex Noninvasive Salivary Antibody Assay for SARS-CoV-2 Infection and Its Application in a Population-Based Survey by Mail.

ABSTRACTNoninvasive salivary antibody immunoassays can enable low-cost epidemiological surveillance of infections. This study involved developing and validating a multiplex suspension immunoassay on the Luminex platform to measure immunoglobulin G (IgG) responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid and spike (S) proteins, and the spike protein’s S1 and S2 subunits and receptor binding domain. Multiple versions of these recombinant proteins acquired from commercial and noncommercial sources were evaluated. Assay development and validation utilized saliva and serum samples from coronavirus disease 2019 (COVID-19) cases procured from commercial sources and negative controls from a prepandemic survey. Saliva was also collected in a demonstration survey by mail involving adult individuals in the United States who were diagnosed with SARS-CoV-2 infection 15 to 80 days prior to sample collection. The survey had an 83% valid sample return rate (192 samples from 38 states). Most COVID-19 cases (93%) reported mildly symptomatic or asymptomatic infections. The final salivary assay based on the best-performing spike and nucleocapsid proteins had a sensitivity of 87.1% (95% bootstrap confidence interval, 82.1 to 91.7%) and specificity of 98.5% (95.0 to 100%) using 227 and 285 saliva samples, respectively. The same assay had 95.9% (92.8 to 98.9%) sensitivity and 100% (98.4 to 100%) specificity in serum (174 and 285 serum samples, respectively). Salivary and serum antibody responses to spike and nucleocapsid proteins were strongly correlated in 22 paired samples (r = 0.88 and r = 0.80, respectively). Antibody responses peaked at approximately 50 days postonset; greater illness severity was associated with stronger responses. This study demonstrated that a salivary antibody assay can be used in large-scale population surveys by mail to better characterize public health impacts of COVID-19.IMPORTANCE Given the enormous impacts of the COVID-19 pandemic, developing tools for population surveillance of infection is of paramount importance. This article describes the development of a multiplex immunoassay on a Luminex platform to measure salivary immunoglobulin G responses to the spike protein, its two subunits and receptor binding domain, and the nucleocapsid protein of SARS-CoV-2. The assay validation utilized serum and saliva samples from prepandemic controls and recent COVID-19 cases. A survey by mail targeting recent COVID-19 cases across the United States also demonstrated the utility of safe, at-home self-collection of saliva. By incorporating multiple SARS-CoV-2 proteins, this assay may differentiate responses to natural SARS-CoV-2 infections from responses to most vaccines. Application of this noninvasive immunoassay in COVID-19 surveillance can help provide estimates of cumulative incidence rates of symptomatic and asymptomatic infections in various communities and subpopulations, temporal patterns of antibody responses, and risk factors for infection.

Comparison of subdural grid and stereoelectroencephalography in a cohort of pediatric patients

ObjectiveTo compare adverse events and outcomes between stereoelectroencephalography (SEEG) and subdural electrode (SDE) implantation in children. MethodsThis was a retrospective analysis of 108 patients who underwent intracranial monitoring with SEEG or SDE implantation at Children’s Hospital Colorado between January 2011 and June 2019. ResultsThere were 47 patients who underwent 53 SEEG implantations and 61 patients who underwent 64 SDE implantations, with an average age of 12.45 years (range: 1.22–19.96 years). Post-implantation imaging was performed in all SEEG implantations and 42 SDE implantations. 38 % and 88 % of SEEG and SDE implantations, respectively, had a hemorrhage of any kind (p < 0.01). Clinically significant hemorrhages did not differ between the two groups, though one death was reported in the SEEG group. No patient undergoing SEEG implantation received blood products compared to 20 % of SDE patients (p < 0.01). The rate of infection in SEEG patients was 4% compared to 33 % for SDE patients (p = 0.01). Resection was completed in 60 % of SEEG patients versus 93 % for SDE patients (p < 0.01). Rate of seizure response was not significantly different between the two groups, with 81 % and 71 % of SEEG and SDE patients, respectively, reaching Engel class I or II at 12 months (p = 0.76). SignificanceIn pediatric patients at a single institution, SEEG is associated with less adverse effects overall yet similar rates of seizure freedom compared to SDE implantation. This includes significantly lower rates of asymptomatic hemorrhage, infection and need for blood transfusion associated with SEEG monitoring. There was no statistical difference in clinically significant hemorrhages between the two groups, although rare in both.

Antibody seroprevalence and rate of asymptomatic infections with SARS-CoV-2 in Austrian hospital personnel

BackgroundThe aims of this study are to determine (i) SARS-CoV-2 antibody positive employees in Austrian trauma hospitals and rehabilitation facilities, (ii) number of active virus carriers (symptomatic and asymptomatic) during the study, (iii) antibody decline in seropositive subjects over a period of around 6 months, (iv) the usefulness of rapid antibody tests for outpatient screening.MethodA total of 3301 employees in 11 Austrian trauma hospitals and rehabilitation facilities of the Austrian Social Insurance for Occupational Risks (AUVA) participated in this open uncontrolled prospective cohort study.Rapid lateral flow tests, detecting a combination of IgM and IgM against SARS-CoV-2), two different types of CLIA (Diasorin, Roche), RT-PCR tests and serum neutralization tests (SNTs) were performed. The tests were conducted twice, with an interval of 42.4 ± 7.7 (Min = 30, Max = 64) days. Positive participants were re-tested with CLIA/SNT at a third time point after 188.0 ± 12.8 days.ResultsOnly 27 out of 3301 participants (0.82%) had a positive antibody test at any time point during the study confirmed via neutralization test. Among positively tested participants in either test, 50.4% did not report any symptoms consistent with common manifestations of COVID-19 during the study period or within the preceding 6 weeks. In the group who tested positive during or prior to study inclusion the most common symptoms of an acute viral illness were rhinitis (21.9%), and loss of taste and olfactory sense (21.9%).Based on the neutralization test as the true condition, the rapid antibody test performed better on serum than whole blood as 84.6% instead of 65.4% could be detected correctly. Concerning both CLIA tests overall the Roche test detected 24 (sensitivity = 88.9%) and the Diasorin test 22 positive participants (sensitivity = 81.5%).In participants with a positive SNT result, a significant drop in neutralizing antibody titre from 31.8 ± 22.9 (Md = 32.0) at T1 to 26.1 ± 17.6 (Md = 21.3) at T2 to 21.4 ± 13.4 (Md = 16.0) at T3 (χ2 = 23.848, df = 2, p < 0.001) was observed (χ2 = 23.848, df = 2, p < 0.001)—with an average time of 42.4 ± 7.7 days between T1 and T2 and 146.9 ± 13.8 days between T2 and T3.ConclusionsDuring the study period (May 11th–August 3rd) only 0.82% were tested positive for antibodies in our study cohort. The antibody concentration decreases significantly over time with 14.8% (4 out of 27) losing detectable antibodies.

Asymptomatic COVID-19 Individuals Tend to Establish Relatively Balanced Innate and Adaptive Immune Responses.

The sharp increase in the proportion of asymptomatic cases and the potential risk of virus transmission have greatly increased the difficulty of controlling the COVID-19 pandemic. The individual immune response is closely associated with clinical outcomes and pathogenic mechanisms of COVID-19. However, the clinical characteristics and immunophenotyping features of immune cells of asymptomatic individuals remain somewhat mysterious. To better understand and predict the disease state and progress, we performed a comprehensive analysis of clinical data, laboratory indexes and immunophenotyping features in 41 patients with SARS-CoV-2 (including 24 asymptomatic cases and 17 symptomatic individuals). Firstly, from the perspective of demographic characteristics, the rate of asymptomatic infection was significantly higher in those with younger age. Secondly, the laboratory test results showed that some indexes, such as CRP (acute phase reaction protein), D-Dimer and fibrinogen (the marker for coagulation) were lower in the asymptomatic group. Finally, symptomatic individuals were prone to establishing a non-protective immune phenotype by abnormally decreasing the lymphocyte count and percentage, abnormally increasing the Th17 percentage and decreasing Treg percentage, which therefore cause an increase in the neutrophil/lymphocyte ratio (NLR), monocytes/lymphocytes ratio (MLR) and Th17/Treg ratio. On the other hand, asymptomatic individuals tended to establish a more effective and protective immune phenotype by maintaining a normal level of lymphocyte count and percentage and a high level of NK cells. At the same time, asymptomatic individuals can establish a relatively balanced immune response through maintaining a low level of monocytes, a relatively low level of Th17 and high level of Treg, which therefore lead to a decrease in MNKR and Th17/Treg ratio and finally the avoidance of excessive inflammatory responses. This may be one of the reasons for their asymptomatic states. This study is helpful to reveal the immunological characteristics of asymptomatic individuals, understand immune pathogenesis of COVID-19 and predict clinical outcomes more precisely. However, owing to small sample sizes, a future study with larger sample size is still warranted.

Universal testing for COVID-19 in patients undergoing cancer treatment during the second outbreak in Brescia.

The impact of coronavirus disease 2019 (COVID-19) has been overwhelming on patients with cancer, who may be at higher risk of developing severe disease. During the second COVID-19 outbreak in Italy, we planned universal microbiologic screening for patients scheduled for antineoplastic treatment. All patients with planned active treatment at Brescia University Radiation Oncology Department were screened for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA with repeated nasopharyngeal swabs (NPS) from October 31, 2020. Treatment continuation, suspension, or delay was modulated for patients testing positive according to clinical presentation. From October 31, 2020, to February 6, 2021, 636 patients were enrolled and 1243 NPS were performed, of which 28 (2.25%) were positive. The infection rate was 2.52%; 81.3% of the patients with a positive NPS were asymptomatic, 2 had mild disease, and 1 severe disease that led to death. All patients already on treatment with mild or asymptomatic COVID-19 carried on the therapy with no or minimal delay. Median delay for patients with infection detected before treatment start was 16.5 days. Detected incidence of COVID-19 was lower during the second outbreak in our patients (2.52% vs 3.23%), despite the extensive testing schedule, and substantiates the high rate of asymptomatic infections and the low mortality among patients with COVID-19 (6.3% vs 38.5% during the first outbreak). Universal SARS-CoV-2 screening for all patients with planned treatment might allow early identification of patients with COVID-19, resulting in timely management that could improve clinical outcomes and prevent spread of the infection.

Examining the interplay between face mask usage, asymptomatic transmission, and social distancing on the spread of COVID-19

COVID-19’s high virus transmission rates have caused a pandemic that is exacerbated by the high rates of asymptomatic and presymptomatic infections. These factors suggest that face masks and social distance could be paramount in containing the pandemic. We examined the efficacy of each measure and the combination of both measures using an agent-based model within a closed space that approximated real-life interactions. By explicitly considering different fractions of asymptomatic individuals, as well as a realistic hypothesis of face masks protection during inhaling and exhaling, our simulations demonstrate that a synergistic use of face masks and social distancing is the most effective intervention to curb the infection spread. To control the pandemic, our models suggest that high adherence to social distance is necessary to curb the spread of the disease, and that wearing face masks provides optimal protection even if only a small portion of the population comply with social distance. Finally, the face mask effectiveness in curbing the viral spread is not reduced if a large fraction of population is asymptomatic. Our findings have important implications for policies that dictate the reopening of social gatherings.

PO-1494 Universal testing for SARS-Cov-2 in patients undergoing anticancer treatment.

Purpose or Objective: the impact of COVID-19 has been overwhelming on cancer patients, who may be at higher risk of developing severe disease. Outstandingly, the aftermath on neoplastic patients is still largely unknown, remarkably regarding SARS-Cov-2 infection during radiotherapy. In this paper we report the experience of our Department, set in Lombardy, one of the regions most affected by the pandemic worldwide. Materials and Methods: data of cancer patients with ongoing on planned active treatment during the first and second “wave” of the pandemics were retrospectively analyzed. We compared a cohort of 402 cancer patients undergoing active treatment from February 24 to April 24, 2020 (when RT-PCR for SARS-Cov-2 on naso-pharyngeal swabs - NPS - were performed only in case of suggestive symptoms and/or contacts at risk) and a cohort represented by all the 636 patients with planned active treatment at Brescia University Radiation Oncology Department from October 31,2020 to February 06, 20121. In the latter group, all the subjects were screened for SARS-Cov-2 RNA with NPS before treatment start and every 10 days during treatment, as for institutional policy. Results: during the first “wave”, dedicated measures allowed an overall limited infection rate of 3.23% (13/402) and mortality of 1.24% (5/402);remarkably, 92.3% of the cases were detected before March 24. Nevertheless, mortality among COVID-19 patients was high (38.5%) and all the patients were symptomatic, with 46.5% presenting with severe disease. Globally, only 2.5% of ongoing treatments were suspended due to suspect or confirmed COVID-19 and 46.2% of positive patients carried on radiotherapy without interruption. During the second “wave”, a universal screening was implemented for all the patients with planned active treatment. A total of 1243 NPS was performed on 636 patients. The infection rate was 2.52% and 81.3% of the patients with a positive NPS was asymptomatic, two had mild disease and one severe disease that lead to death. All the patients already on treatment with mild or asymptomatic COVID-19 carried on the therapy with no or minimal delay. Median delay for patients with infection detected before treatment start was 16.5 days. Conclusion: detected incidence of COVID-19 was lower during the second outbreak in our patients (2.52% vs 3.23%), despite the extensive testing schedule that also substantiates the high rate of asymptomatic infections and the low mortality among COVID-19 patients (6.3% vs 38.5% during the first outbreak). A universal SARS-Cov-2 screening for all the patients with planned treatment might allow an early identification of COVID-19 patients, resulting in a timely management that could improve clinical outcomes and prevent the spread of the infection.

A Longitudinal, Clinical, and Spatial Epidemiologic Analysis of a Large COVID-19 Long-Term Care Home Outbreak

ObjectivesCOVID-19 has had devastating effects on long-term care homes across much of the world, and especially within Canada, with more than 50% of the mortality from COVID-19 in 2020 in these homes. Understanding the way in which the virus spreads within these homes is critical to preventing further outbreaks. DesignRetrospective chart review. Settings and ParticipantsLong-term care home residents and staff in Ontario, Canada. MethodsWe conducted a longitudinal study of a large long-term care home COVID-19 outbreak in Ontario, Canada, using electronic medical records, public health records, staff assignments, and resident room locations to spatially map the outbreak through the facility. ResultsBy analyzing the outbreak longitudinally, we were able to draw 3 important conclusions: (1) 84.5% had typical COVID-19 symptoms and only 15.5% of residents had asymptomatic infection; (2) there was a high attack rate of 85.8%, which appeared to be explained by a high degree of interconnectedness within the home exacerbated by staffing shortages; and (3) clustering of infections within multibedded rooms was common. Conclusion and ImplicationsLow rates of asymptomatic infection suggest that symptom-based screening in residents remains very important for detecting outbreaks, a high degree of interconnectedness explains the high attack rate, and there is a need for improved guidance for homes with multibedded rooms on optimizing resident room movement to mitigate spread of COVID-19 in long-term care homes.

Investigation on Norovirus prevalence in catering companies and train station in Beijing during non-epidemic season in 2019

Objective: To study the prevalence of Norovirus infection among kitchen workers in Beijing, and the contamination status of Norovirus in catering companies and train station. Methods: A cross-sectional survey was conducted to collect anal swab specimens and environmental specimens from catering companies in 16 districts of Beijing and in 3 big train stations. Norovirus nucleic acid was detected by fluorescence quantitative PCR. The contamination status of Norovirus in the environment and the asymptomatic infection status of kitchen workers was analyzed in this study. Results: A total of 650 catering companies were investigated. 1 302 anal swabs or stool specimens and 2 600 environmental swabs were collected and tested. Among the 644 catering companies out of train stations, 1 290 anal swabs or stool specimens and 2 576 environmental swabs were collected and tested. The asymptomatic infection rate of Norovirus was 0.85% (11/1 290) among kitchen workers of the catering companies out of the train stations, while the positive rate of norovirus contamination in the environment was 0.04% (1/2 576). Norovirus was not detected in the specimens collected from the kitchen workers and the environment of the catering companies in train stations. Conclusion: During the non-epidemic season of Norovirus in 2019, the infection rate of Norovirus among kitchen workers in Beijing is low, and the environment is contaminated by Norovirus.

Preliminary Assessment of Chinese Strategy in Controlling Reemergent Local Outbreak of COVID-19.

Reemergent local outbreaks of coronavirus disease 2019 (COVID-19) have occurred in China, yet few Chinese response strategies and its evaluation have been reported. This study presents a preliminary assessment of Chinese strategy in controlling reemergent local outbreaks of COVID-19. Time course of accumulative and daily new cases and time-varying reproductive numbers (Rt) of outbreak areas were presented. The asymptomatic rate, days required to control the outbreaks, seeding time (ST), and doubling time (DT) of areas with over 96 reemergent cases were calculated. National and local year-on-year growth rates of gross domestic product (GDP) were presented. Accumulative numbers of 30, 8, 11, 430, 15, 139, 1,067, 382, 42, and 94 confirmed reemergent COVID-19 cases were diagnosed in Hulun Buir, Shanghai, Tianjin, Kashgar, Qingdao, Dalian, Urumchi, Beijing, Jilin, and Harbin, respectively. Among them, maximum rate of asymptomatic infections was 81.9%. Time required to control the local outbreaks in the areas given above varied from 29 to 51 days. After activation of outbreak responses, the late-stage DTs of Kashgar, Urumchi, Beijing, and Dalian were apparently lengthened compared to the early-stage DTs. Although the year-on-year GDP growth rate of Urumchi was slightly affected, the GDP growth rate of Dalian, Beijing, Jilin, and Harbin kept rising during the reemergence. Moreover, the year-on-year GDP growth rate of Mainland China turned positive regardless of the reemergent local outbreaks. In general, the Chinese strategy to maintain the status of no or minimal transmission was effective in balancing the control of COVID-19 reemergent local outbreak and the recovery of economy.

Predicting SARS-CoV-2 Asymptomatic Infection Rate of Inpatients: A Time Series Analysis

Background: Asymptomatic SARS-CoV-2 infections play a crucial role in viral transmission. However, they are often difficult to identify given that widespread surveillance has not been the norm. We sought to determine whether COVID-19 rates reported at the county level could predict the positivity rates for SARS-CoV-2 among asymptomatic patients tested in a large academic health system. Methods: This observational study was conducted from April 23, 2020, to December 10, 2020, at Froedtert Health (FH) system, the largest academic health system in Wisconsin. On April 23, 2020, FH implemented SARS-CoV-2 surveillance among all consecutive admissions not suspected of COVID-19, all patients scheduled for elective procedures and deliveries, and all asymptomatic patients with known exposures. Samples were processed by the FH laboratory using molecular methods (RT-PCR). To obtain the daily number of newly confirmed COVID-19 cases in Milwaukee County, we accessed the Wisconsin Department of Health Services publicly available COVID-19 database. For the purpose of this study, COVID-19 rates were defined as the percentage of positive tests among all daily tests performed at the county level, while SARS-CoV-2 positivity rates were the percentage of positive tests among all daily surveillance tests performed at FH among asymptomatic patients. The association between COVID-19 rates in Milwaukee County and asymptomatic rates at FH were assessed using an autoregressive moving average time series analysis. To examine the association between these rates, we fitted a seventh-order autoregression for the residuals based on autocorrelation function and partial autocorrelation function plots of the residuals from linear regression. Results: From April 23, 2020, to December 10, 2020, there were 2,347 new asymptomatic infections detected at FH and 75,196 new COVID-19 cases reported in Milwaukee County. Figure 1 shows the time-series plot of asymptomatic SARS-CoV-2 positivity rates at FH and Figure 2 shows COVID-19 rates in Milwaukee County. As the COVID-19 rate in Milwaukee County increased by 1 unit, the asymptomatic infection rate in FH decreased by 0.024 unit (95% CI, −0.053 to 0.004; P = .095) after accounting for autocorrelation over time. Thus, there was no association between these rates. Conclusions: The positivity rates among asymptomatic patients at a large medical center were not predicted by the positivity rate at the county level. This finding suggests that the epidemiology at a county level may be determined by pockets in the population who may not interact, and thus not affect, the positivity rates among asymptomatic patients served by a hospital system within the county.Funding: NoDisclosures: None

Covid-19 vaccination in patients with multiple myeloma: Focus on immune response.

Covid-19 vaccination in patients with multiple myeloma: Focus on immune response.

Antibody Responses to SARS-CoV-2 Following an Outbreak Among Marine Recruits With Asymptomatic or Mild Infection.

We investigated serological responses following a SARS-CoV-2 outbreak in spring 2020 on a US Marine recruit training base. 147 participants that were isolated during an outbreak of respiratory illness were enrolled in this study, with visits approximately 6 and 10 weeks post-outbreak (PO). This cohort is comprised of young healthy adults, ages 18-26, with a high rate of asymptomatic infection or mild symptoms, and therefore differs from previously reported longitudinal studies on humoral responses to SARS-CoV-2, which often focus on more diverse age populations and worse clinical presentation. 80.9% (119/147) of the participants presented with circulating IgG antibodies against SARS-CoV-2 spike (S) receptor-binding domain (RBD) at 6 weeks PO, of whom 97.3% (111/114) remained positive, with significantly decreased levels, at 10 weeks PO. Neutralizing activity was detected in all sera from SARS-CoV-2 IgG positive participants tested (n=38) at 6 and 10 weeks PO, without significant loss between time points. IgG and IgA antibodies against SARS-CoV-2 RBD, S1, S2, and the nucleocapsid (N) protein, as well neutralization activity, were generally comparable between those participants that had asymptomatic infection or mild disease. A multiplex assay including S proteins from SARS-CoV-2 and related zoonotic and human endemic betacoronaviruses revealed a positive correlation for polyclonal cross-reactivity to S after SARS-CoV-2 infection. Overall, young adults that experienced asymptomatic or mild SARS-CoV-2 infection developed comparable humoral responses, with no decrease in neutralizing activity at least up to 10 weeks after infection.

COVID-19: Is it safe now? Study of asymptomatic infection spread and quantity risk based on SAIR model

Based on the characteristic of the COVID-19 asymptomatic infection, and due to the shortage of traditional mathematical models of transmission dynamics of infectious diseases, we propose a new SAIR model. This SAIR model fully considers the infectious characteristics of asymptomatic cases and the transformation characteristics between the four kinds case. According to the data released by the National Health Commission of P.R.C, the model parameters are calculated, and the transmission process of the COVID-19 is simulated dynamically. It is found that the SAIR model data are in good agreement with the actual data, and the time characteristics of the infection rate are particularly accurate, proving the accuracy and effectiveness of the model. Then, on the basis of the differences between the model data and the real data, the standard deviation of the error is calculated. From the standard deviation, the functional intervals of the confirmed infection rate and the asymptomatic infection rate, the interval of the total number of cases in the model, and the interval of the number of asymptomatic cases in the society are also calculated. The number of asymptomatic cases in society is of important and realistic significance for the assessment of risk and subsequent control measures. Then, according to the dynamic simulation data of the model with changed value of parameters, the remarkable effects of strict quarantines are discussed. Finally, the possible direction of further study is given.

Viral dynamics and antibody responses in people with asymptomatic SARS-CoV-2 infection

Over 40% of the coronavirus disease 2019 (COVID-19) COVID-19 patients were asymptomatically infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the immune responses of these asymptomatic individuals is a critical factor for developing the strategy to contain the COVID-19 pandemic. Here, we determined the viral dynamics and antibody responses among 143 asymptomatic individuals identified in a massive screening of more than 5 million people in eight districts of Wuhan in May 2020. Asymptomatic individuals were admitted to the government-designated centralized sites in accordance with policy. The incidence rate of asymptomatic infection is ~2.92/100,000. These individuals had low viral copy numbers (peaked at 315 copies/mL) and short-lived antibody responses with the estimated diminish time of 69 days. The antibody responses in individuals with persistent SARS-CoV-2 infection is much longer with the estimated diminish time of 257 days. These results imply that the immune responses in the asymptomatic individuals are not potent enough for preventing SARS-CoV-2 re-infection, which has recently been reported in recovered COVID-19 patients. This casts doubt on the efficacy of forming “herd-immunity” through natural SARS-CoV-2 infection and urges for the development of safe and effective vaccines.

SARS-CoV-2 IgG Seropositivity and Acute Asymptomatic Infection Rate among Firefighter First Responders in an Early Outbreak County in California

Objective: Firefighter first responders and other emergency medical services (EMS) personnel have been among the highest risk healthcare workers for illness during the SARS-CoV-2 pandemic. We sought to determine the rate of seropositivity for SARS-CoV-2 IgG antibodies and of acute asymptomatic infection among firefighter first responders in a single county with early exposure in the pandemic. Methods: We conducted a cross-sectional study of clinically active firefighters cross-trained as paramedics or EMTs in the fire departments of Santa Clara County, California. Firefighters without current symptoms were tested between June and August 2020. Our primary outcomes were rates of SARS-CoV-2 IgG antibody seropositivity and SARS-CoV-2 RT-PCR swab positivity for acute infection. We report cumulative incidence, participant characteristics with frequencies and proportions, and proportion positive and associated relative risk (with 95% confidence intervals). Results: We enrolled 983 out of 1339 eligible participants (response rate: 73.4%). Twenty-five participants (2.54%, 95% CI 1.65-3.73) tested positive for IgG antibodies and 9 (0.92%, 95% CI 0.42-1.73) tested positive for SARS-CoV-2 by RT-PCR. Our cumulative incidence, inclusive of self-reported prior positive PCR tests, was 34 (3.46%, 95% CI 2.41-4.80). Conclusion: In a county with one of the earliest outbreaks in the United States, the seroprevalence among firefighter first responders was lower than that reported by other studies of frontline health care workers, while the cumulative incidence remained higher than that seen in the surrounding community.