Seroprevalence, seroconversion, and seroreversion of infection-induced SARS-CoV-2 antibodies among a cohort of children and adolescents in Montreal, Canada (preprint)

Importance: Repeated serological testing for SARS-CoV-2 allows the monitoring of antibody dynamics in populations, including detecting infections that are missed by RT-PCR or antigen testing. Understanding the factors associated with seroconversion and seroreversion as well as the duration of infection-induced antibodies can also inform public health recommendations regarding disease prevention and mitigation efforts. Objective: To use serological testing to assess the prevalence, seroconversion, and seroreversion of infection-induced SARS-CoV-2 antibodies in children and adolescents in Montreal, Canada. Design: This analysis reports on three rounds of data collection from a prospective cohort study (Enfants et COVID-19: Etude de seroprevalence [EnCORE]). The study rounds occurred as follows: Round 1 October 2020-March 2021, Round 2 May to July 2021, and Round 3 November 2021 to January 2022. Most Round 3 samples were collected prior to the spread of the Omicron BA.1 variant in Quebec. Setting: Population-based sample. Participants: Children and adolescents aged 2 to 17 years in Montreal, Canada. Exposure: Potential exposure to SARS-CoV-2. Main Outcomes and Measures: Participants provided dried blood spots (DBS) for antibody detection and parents completed online questionnaires for sociodemographics and COVID-19 symptoms and testing history. The serostatus of participants was determined by enzyme-linked immunosorbent assays (ELISAs) using the receptor-binding domain (RBD) from the spike protein and the nucleocapsid protein (N) as antigens. We estimated seroprevalence for each round of data collection and by participant and household characteristics. Seroconversion rates were calculated as were the likelihoods of remaining seropositive at six months and one year. Results: The study included DBS samples from 1 632, 936, and 723 participants in the first, second, and third rounds of data collection, respectively. The baseline seroprevalence was 5.8% (95% CI 4.8-7.1), which increased to 10.5% and 10.9% for the respective follow-ups (95% CI 8.6-12.7; 95% CI 8.8-13.5). The overall average crude rate of seroconversion over the study period was 12.7 per 100 person-years (95% CI 10.9-14.5). Adjusted hazard rates of seroconversion by child and household characteristics showed higher rates in children who were female, whose parent identified as a racial or ethnic minority, and in households with incomes less than 100K. The likelihood of remaining seropositive at six months was 67% (95% CI 59-76) and dropped to 19% (95% CI 11%-33%) at one year. Conclusions and Relevance: The data reported here provide estimates of pre-Omicron seroprevalence, seroconversion rates and time to seroreversion in a population-based cohort of children and adolescents. Serological studies continue to provide valuable contributions for infection prevalence estimates and help us better understand the dynamics of antibody levels following infection. Continued study of seroconversion and seroreversion can inform public health recommendations such as COVID-19 vaccination and booster schedules.

Epidemiology and role of SARS-CoV-2 Linkage in Paediatric Inflammatory Multisystem Syndrome (PIMS): A Canadian Paediatric Surveillance Program National Prospective Study (preprint)

Background: Paediatric inflammatory multisystem syndrome (PIMS) is a rare but serious condition temporally associated with SARS CoV2 infection. Using the Canadian Paediatric Surveillance Program (CPSP), a national surveillance system, we aimed to 1) study the impact of SARS CoV2 linkage on clinical and laboratory characteristics, and outcomes in hospitalized children with PIMS across Canada 2) identify risk factors for ICU admission, and 3) establish the minimum national incidence of hospitalizations due to PIMS and compare it to acute COVID 19. Methods: Weekly online case reporting was distributed to the CPSP network of more than 2800 pediatricians, from March 2020 to May 2021. Comparisons were made between cases with respect to SARS CoV2 linkage. Multivariable modified Poisson regression was used to identify risk factors for ICU admission and Minimum incidence proportions were calculated. Findings: In total, 406 PIMS cases were analyzed, of whom 202 (49.8%) had a positive SARS CoV2 linkage, 106 (26.1%) had a negative linkage, and 98 (24.1%) had an unknown linkage. The median age was 5.4 years (IQR 2.5 to 9.8), 60% were male, and 83% had no identified comorbidities. Compared to cases with a negative SARS CoV2 linkage, children with a positive SARS CoV2 linkage were older (8.1 years [IQR 4.2 to 11.9] vs 4.1 years [IQR 1.7 to 7.7]; p<0.001), had more cardiac involvement (58.8% vs 37.4%; p<0.001), gastrointestinal symptoms (88.6% vs 63.2%; p<0.001), and shock (60.9% vs 16.0%; p<0.001). At risk groups for ICU admission include children >=6 years and those with a positive SARS CoV2 linkage. No deaths were reported. The minimum incidence of PIMS hospitalizations during the study period was 5.6 hospitalizations per 100,000 population <18 years. Interpretation: While PIMS is rare, almost 1 in 3 hospitalized children required ICU admission and respiratory/hemodynamic support, particularly those >=6 years and with a positive SARS CoV2 linkage. Funding: Financial support for the CPSP was received from the Public Health Agency of Canada.

SARS-CoV-2 infection in technology dependent children: a multicenter case series (preprint)

Purpose: The objective of this study was to describe the clinical course and outcomes in children with technology-dependence (TD) hospitalized with SARS-CoV-2 infection.Methods: Seventeen pediatric hospitals (15 Canadian and one each in Iran and Costa Rica) included children up to 17 years of age admitted February 1, 2020, through May 31, 2021, with detection of SARS-CoV-2. For those with TD, data were collected on demographics, clinical course and outcome. Results: Of 691 children entered in the database, 42 (6%) had TD of which 22 had feeding tube dependence only, 9 were on supplemental oxygen only, 3 had feeding tube dependence and were on supplemental oxygen, 2 had a tracheostomy but were not ventilated, 4 were on non-invasive ventilation, and 2 were on mechanical ventilation prior to admission. Three of 42 had incidental SARS-CoV-2 infection. Two with end-stage underlying conditions were transitioned to comfort care and died. Sixteen (43%) of the remaining 37 cases required increased respiratory support from baseline due to COVID-19 while 21 (57%) did not. All survivors were discharged home.Conclusion: Children with TD appear to have an increased risk of COVID-19 hospitalization. However, in the absence of end-stage chronic conditions, all survived to discharge. 

Risk factors for severe COVID-19 in hospitalized children in Canada: A national prospective study from March 2020--May 2021 (preprint)

Background: Children living with chronic comorbid conditions are at increased risk for severe COVID-19, though there is limited evidence regarding the risks associated with specific conditions and which children may benefit from targeted COVID-19 therapies. The objective of this study was to identify factors associated with severe disease among hospitalized children with COVID-19 in Canada. Methods: We conducted a national prospective study on hospitalized children with microbiologically confirmed SARS-CoV-2 infection via the Canadian Paediatric Surveillance Program from April 2020--May 2021. Cases were reported voluntarily by a network of >2800 paediatricians. Hospitalizations were classified as COVID-19-related, incidental infection, or infection control/social admissions. Severe disease (among COVID-19-related hospitalizations only) was defined as disease requiring intensive care, ventilatory or hemodynamic support, select organ system complications, or death. Risk factors for severe disease were identified using multivariable Poisson regression, adjusting for age, sex, concomitant infections, and timing of hospitalization. Findings: We identified 544 children hospitalized with SARS-CoV-2 infection, including 60{middle dot}7% with COVID-19-related disease and 39{middle dot}3% with incidental infection or infection control/social admissions. Among COVID-19-related hospitalizations (n=330), the median age was 1{middle dot}9 years (IQR 0{middle dot}1--13{middle dot}3) and 43{middle dot}0% had chronic comorbid conditions. Severe disease occurred in 29{middle dot}7% of COVID-19-related hospitalizations (n=98/330), most frequently among children aged 2-4 years (48{middle dot}7%) and 12-17 years (41{middle dot}3%). Comorbid conditions associated with severe disease included technology dependence (adjusted risk ratio [aRR] 2{middle dot}01, 95% confidence interval [CI] 1{middle dot}37-2{middle dot}95), neurologic conditions (e.g. epilepsy and select chromosomal/genetic conditions) (aRR 1{middle dot}84, 95% CI 1{middle dot}32-2{middle dot}57), and pulmonary conditions (e.g. bronchopulmonary dysplasia and uncontrolled asthma) (aRR 1{middle dot}63, 95% CI 1{middle dot}12-2{middle dot}39). Interpretation: While severe outcomes were detected at all ages and among patients with and without comorbidities, neurologic and pulmonary conditions as well as technology dependence were associated with increased risk of severe COVID-19. These findings may help guide vaccination programs and prioritize targeted COVID-19 therapies for children. Funding: Financial support for the CPSP was received from the Public Health Agency of Canada.

Adequacy of serial self-performed SARS-CoV-2 rapid antigen-detection testing for longitudinal mass screening in the workplace (preprint)

Importance: Longitudinal mass testing using rapid antigen detection tests (RADT) for serial screening of asymptomatic persons has been proposed for preventing SARS-CoV-2 community transmission. The feasibility of this strategy relies on implementation of accurate self-performed RADT testing where people live, work, or attend school. Objective: To quantify the adequacy of serial self-performed SARS-CoV-2 RADT testing in the workplace, in terms of the frequency of correct execution of procedural steps and accurate interpretation of the range of possible RADT results. We compared results using the instructions provided by the manufacturer to those with modified instructions that were informed by the most frequent or most critical errors we observed. Design: Repeated cross-sectional, diagnostic accuracy study performed prospectively in the field. Setting: Businesses in Montreal, Quebec, Canada, with at least 2 active cases of SARS-CoV-2 infection. Participants: Untrained, asymptomatic persons in their workplace, not meeting Public Health quarantine criteria. Exposures: A Modified Quick Reference Guide compared to the original manufacturer's instructions. Main Outcome(s) and Measure(s): The difference in the proportions of correctly performed procedural steps, and the difference in proportions of correctly interpreted RADT proficiency panel results. The secondary outcome, among subjects with two self-testing visits, compared the second to the first self-test visit using the same measures. Results: Overall, 1892 tests were performed among 647 subjects. For self-test visit 1, significantly better accuracy in test interpretation was observed using the Modified Quick Reference Guide for weak positive (55.6% vs. 12.3%; 43.3 percentage point improvement, 95% confidence interval [CI] 33.0%-53.8%), positive (89.6% vs. 51.5%; 38.1% difference, 95%CI 28.5%-47.5%), strong positive (95.6% vs. 84.0%; 11.6% improvement, 95%CI 6.8%-16.3%) and invalid (87.3% vs. 77.3%; 10.0% improvement, 95%CI 3.8%-16.3%) tests. Use of the modified guide was associated with smaller, statistically significant, improvements on self-test visit 2. For procedural steps identified as critical for the validity of test results, adherence to procedural testing steps did not differ meaningfully according to instructions provided or reader experience. Conclusions and Relevance: Longitudinal mass RADT testing for SARS-CoV-2 can be accurately self-performed in an intended-use setting; this work provides evidence for how to optimise performance.

Clinical manifestations and disease severity of SARS-CoV-2 infection among infants in Canada (preprint)

ImportanceThere are limited data on outcomes of SARS-CoV-2 infection among infants (<1 year of age). In the absence of approved vaccines for infants, understanding characteristics associated with hospitalization and severe disease from COVID-19 in this age group will help inform clinical management and public health interventions. ObjectiveThe objective of this study was to describe the clinical manifestations, disease severity, and characteristics associated with hospitalization among infants infected with the initial strains of SARS-CoV-2. DesignProspective study of infants with SARS-CoV-2 from April 8th 2020 to May 31st 2021. SettingNational study using the infrastructure of the Canadian Paediatric Surveillance Program, reporting inpatients and outpatients seen in clinics and emergency departments. ParticipantsInfants <1 year of age with microbiologically confirmed SARS-CoV-2 infection. ExposureInfant-level characteristics associated with hospitalization for COVID-19. Main outcomes and MeasuresCases were classified as either: 1) Non-hospitalized patient with SARS-CoV-2 infection; 2) COVID-19-related hospitalization; or 3) non-COVID-19-related hospitalization (e.g., incidentally detected SARS-CoV-2). Case severity was defined as asymptomatic, outpatient care, mild (inpatient care), moderate or severe disease. Multivariable logistic regression was performed to identify characteristics associated with hospitalization. ResultsA total of 531 cases were reported, including 332 (62.5%) non-hospitalized and 199 (37.5%) hospitalized infants. Among hospitalized infants, 141 of 199 infants (70.9%) were admitted because of COVID-19-related illness, and 58 (29.1%) were admitted for reasons other than acute COVID-19. Amongst all cases with SARS-CoV-2 infection, the most common presenting symptoms included fever (66.5%), coryza (47.1%), cough (37.3%) and decreased oral intake (25.0%). In our main analysis, infants with a comorbid condition had higher odds of hospitalization compared to infants with no comorbid conditions (aOR=4.53, 2.06-9.97), and infants <1 month had higher odds of hospitalization then infants aged 1-3 months (aOR=3.78, 1.97-7.26). In total, 20 infants (3.8%) met criteria for severe disease. Conclusions and RelevanceWe describe one of the largest cohorts of infants with SARS-CoV-2 infection. Overall, severe COVID-19 in this age group is uncommon with most infants having mild disease. Comorbid conditions and younger age were associated with COVID-19-related hospitalization amongst infants. Key PointsO_ST_ABSQuestionC_ST_ABSWhat are the spectrum of illness, disease severity, and characteristics associated with hospitalization in infants with SARS-CoV-2 infection? FindingsA total of 531 cases were reported to the Canadian Paediatric Surveillance Program, including 332 (62.5%) non-hospitalized and 199 (37.5%) hospitalized infants. In total, 20 infants met criteria for severe disease (3.8%). Infants characteristics associated with admission included age of less than one month and comorbid conditions. MeaningThis study provides data on the spectrum of disease, severity, and characteristics associated with admission due to COVID-19 in infants, which informs clinical management and public health interventions in this specific population.

Hematologic manifestations of SARS-CoV-2 infection and MIS-C in hospitalized children. Results of the PICNIC registry. (preprint)

Introduction: Hematologic complications of SARS-CoV-2 infection are well described in hospitalized adults with correlation to adverse outcomes. Information published in children has been limited. Methods: An international multi-centered retrospective registry was established to collect data on the clinical manifestations of SARS-CoV-2 or multisystem inflammatory syndrome (MIS-C) in hospitalized children between February 1, 2020 – May 31, 2021. This sub-study focused on hematologic manifestations. Study variables included patient demographics, comorbidities, clinical presentation, course, laboratory parameters, management, and outcomes. Results: Nine hundred and eighty-five children were enrolled and 915 (93%) had clinical information available; 385 (42%) had symptomatic SARS-CoV-2 infection upon admission, 288 had MIS-C (31.4%) and 242 (26.4%) had alternate diagnosis with SARS-CoV-2 identified incidentally. During hospitalization, 10 children (1%) experienced a thrombotic event, 16 (1.7%) had hemorrhage and 2 (0.2%) had both thrombotic and hemorrhagic episodes. Significant prothrombotic comorbidities included congenital heart disease (p-value = 0.007), central venous catheter (p = 0.04) in children with primary SARS-CoV-2 infection; and obesity (p-value= 0.002), cytokine storm (p= 0.012) in those with MIS-C. Significant pro- hemorrhagic conditions included age > 10 years (p = 0.04), CVC (p= 0.03) in children with primary SARS-CoV-2infection; and thrombocytopenia (0.001), cytokine storm (0.02) in those with MIS-C. Eleven patients died (1.2 %) with no deaths attributed to thrombosis or hemorrhage Conclusion: Thrombotic and hemorrhagic complications are uncommon in children with SARS-CoV-2 infection and observed with underlying co-morbid conditions. Understanding the complete spectrum of hematologic complications in children with SARS-CoV-2 infection or MIS-C requires ongoing multi-center studies.

Infants Hospitalized for Acute COVID-19: Disease Severity in a Multicenter Cohort Study (preprint)

Age is the most important determinant of COVID-19 severity. Infectious disease severity by age is typically J-shaped, with infants and the elderly carrying a high burden of disease. We report on the comparative disease severity between infants and older children in a multicenter retrospective cohort study of children 0 to 17 year old admitted for acute COVID-19 February 2020 through May 2021 in 17 pediatric hospitals. We compare clinical and laboratory characteristics and estimate the association between age group and disease severity using ordinal logistic regression. We found that infants comprised one third of cases, but were admitted for a shorter period (median 3 days IQR 2-5 versus 4 days IQR 2-7), had a lower likelihood to have an increased C-reactive protein and had half the odds of older children of having severe or critical disease (OR 0.50 (95% Confidence Interval 0.32-0.78)). Conclusion: When compared to older children, there appeared to be a lower threshold to admit infants but their length of stay is shorter and they have a lower odds than older children of progressing to severe or critical disease.

Global epidemiology of SARS-CoV-2 infection: a systematic review and meta-analysis of standardized population-based seroprevalence studies, Jan 2020-Oct 2021 (preprint)

Background COVID-19 case data underestimates infection and immunity, especially in low- and middle-income countries (LMICs). We meta-analyzed standardized SARS-CoV-2 seroprevalence studies to estimate global seroprevalence. Objectives/Methods We conducted a systematic review and meta-analysis, searching MEDLINE, Embase, Web of Science, preprints, and grey literature for SARS-CoV-2 seroprevalence studies aligned with the WHO UNITY protocol published between 2020-01-01 and 2021-10-29. Eligible studies were extracted and critically appraised in duplicate. We meta-analyzed seroprevalence by country and month, pooling to estimate regional and global seroprevalence over time; compared seroprevalence from infection to confirmed cases to estimate under-ascertainment; meta-analyzed differences in seroprevalence between demographic subgroups; and identified national factors associated with seroprevalence using meta-regression. PROSPERO: CRD42020183634. Results We identified 396 full texts reporting 736 distinct seroprevalence studies (41% LMIC), including 355 low/moderate risk of bias studies with national/sub-national scope in further analysis. By April 2021, global SARS-CoV-2 seroprevalence was 26.1%, 95% CI [24.6-27.6%]. Seroprevalence rose steeply in the first half of 2021 due to infection in some regions (e.g., 18.2% to 45.9% in Africa) and vaccination and infection in others (e.g., 11.3% to 57.4% in the Americas high-income countries), but remained low in others (e.g., 0.3% to 1.6% in the Western Pacific). In 2021 Q1, median seroprevalence to case ratios were 1.9:1 in HICs and 61.9:1 in LMICs. Children 0-9 years and adults 60+ were at lower risk of seropositivity than adults 20-29. In a multivariate model using data pre-vaccination, more stringent public health and social measures were associated with lower seroprevalence. Conclusions Global seroprevalence has risen considerably over time and with regional variation, however much of the global population remains susceptible to SARS-CoV-2 infection. True infections far exceed reported COVID-19 cases. Standardized seroprevalence studies are essential to inform COVID-19 control measures, particularly in resource-limited regions.

Risk factors for severe PCR-positive SARS-CoV-2 infection in hospitalized children: a multicenter cohort study (preprint)

Importance: Children are less likely than adults to have severe outcomes from SARS-CoV-2 infection and the corresponding risk factors are not well established. Objective: To identify risk factors for severe disease in symptomatic children hospitalized for PCR-positive SARS-CoV-2 infection. Design: Cohort study, enrollment from February 1, 2020 until May 31, 2021 Setting 15 children's hospitals in Canada, Iran, and Costa Rica Participants: Patients <18 years of age hospitalized with symptomatic SARS-CoV-2 infection, including PCR-positive multisystem inflammatory syndrome in children (MIS-C) Exposures: Variables assessed for their association with disease severity included patient demographics, presence of comorbidities, clinical manifestations, laboratory parameters and chest imaging findings. Main Outcomes and Measures: The primary outcome was severe disease defined as a WHO COVID-19 clinical progression scale of [≥]6, i.e., requirement of non-invasive ventilation, high flow nasal cannula, mechanical ventilation, vasopressors, or death. Multivariable logistic regression was used to evaluate factors associated with severe disease. Results: We identified 403 hospitalizations. Median age was 3.78 years (IQR 0.53-10.77). At least one comorbidity was present in 46.4% (187/403) and multiple comorbidities in 18.6% (75/403). Severe disease occurred in 33.8% (102/403). In multivariable analyses, presence of multiple comorbidities (adjusted odds ratio 2.24, 95% confidence interval 1.04-4.81), obesity (2.87, 1.19-6.93), neurological disorder (3.22, 1.37-7.56), anemia, and/or hemoglobinopathy (5.88, 1.30-26.46), shortness of breath (4.37, 2.08-9.16), bacterial and/or viral coinfections (2.26, 1.08-4.73), chest imaging compatible with COVID-19 (2.99, 1.51-5.92), neutrophilia (2.60, 1.35-5.02), and MIS-C diagnosis (3.86, 1.56-9.51) were independent risk factors for severity. Comorbidities, especially obesity (40.9% vs 3.9%, p<0.001), were more frequently present in adolescents [≥]12 years of age. Neurological disorder (3.16, 1.19-8.43) in children <12 years of age and obesity (3.21, 1.15-8.93) in adolescents were the specific comorbidities associated with disease severity in age-stratified adjusted analyses. Sensitivity analyses excluding the 81 cases with MIS-C did not substantially change the identified risk factors. Conclusions and Relevance: Pediatric risk factors for severe SARS-CoV-2 infection vary according to age and can potentially guide vaccination programs and treatment approaches in children.

Specificity of SARS-CoV-2 antibody-detection assays against S and N protein among pre-COVID-19 sera from patients with protozoan and helminth parasitic infections (preprint)

BackgroundWe aimed to assess the specificity of SARS-CoV-2 antibody detection assays among people with known tissue-borne parasitic infections. MethodsWe tested three SARS-CoV-2 antibody-detection assays (cPass SARS-CoV-2 Neutralization Antibody Detection Kit, Abbott SARS-CoV-2 IgG assay, and STANDARD Q COVID-19 IgM/IgG Combo Rapid Test) among 559 pre-COVID-19 sera. ResultsThe specificity of assays was 95-98% overall. However, lower specificity was observed among sera from patients with protozoan infections of the reticuloendothelial system, such as human African trypanosomiasis (Abbott Architect; 88% [95%CI 75-95]), visceral leishmaniasis (SD RDT IgG; 80% [95%CI 30-99]), and from patients with recent malaria from a holoendemic area of Senegal (ranging from 91% for Abbott Architect and SD RDT IgM to 98-99% for cPass and SD RDT IgG). For specimens from patients with evidence of past or present helminth infection overall, test specificity estimates were all [≥] 96%. Sera collected from patients clinically suspected of parasitic infections that tested negative for these infections yielded a specificity of 98-100%. The majority (>85%) of false-positive results were positive by only one assay. ConclusionsThe specificity of SARS-CoV-2 serological assays among sera from patients with tissue-borne parasitic infections was below the threshold required for decisions about individual patient care. Specificity is markedly increased by the use of confirmatory testing with a second assay. Finally, the SD RDT IgG proved similarly specific to laboratory-based assays and provides an option in low-resource settings when detection of anti-SARS-CoV-2 IgG is indicated.

Seroprevalence of Anti-SARS-CoV-2 Antibodies Among School and Daycare Children: Baseline Results From a Cohort Study in Montreal, Canada (preprint)

Background: Montreal was one of the highest COVID-19 burdened cities in Canada during the first and second waves of the pandemic. We estimated the seroprevalence of SARS-CoV-2 in children and teenagers in four neighbourhoods of Montreal, Canada.Methods: All children attending selected schools and daycares within the four neighbourhoods were invited to participate in the study. Study participation included an online questionnaire that parents completed, followed by at-home dried blood spot (DBS) collection. Serological results were analyzed using a research-based ELISA assay. Statistical analyses included multivariable logistic regression models to calculate average marginal effects and robust standard errors to account for clustering by school or daycare. Several different sociodemographic differences were examined between the seronegative and seropositive children.Findings: There were 30 daycares, 22 primary schools, and 11 secondary schools that participated in the study with 1,632 participants having provided a DBS sample that was of sufficient quality for the serological analysis. The average seroprevalence was 5·8% (95%CI 4·6 to 7·0) but increased over time from 3·2% (95% CI 0·7 to 5·8) in October-November 2020 to 8.4% (95% CI 4·4 to 12·4) in March-April 2021. The children of visible minority parents were nearly twice as likely to be seropositive as children of non-visible minority parents (1·93, 95%CI 1·11 to 2·75). Interpretation: Our results provide a benchmark of the seroprevalence status in Canadian children and provide further evidence of COVID-19 inequities. It will be important to continue monitoring the serological status of children, particularly in the context of new COVID-19 variants of concern and in the absence of mass vaccination campaigns targeting young children.Funding Information: Public Health Agency of Canada through the COVID-19 Immunity Task Force.Declaration of Interests: All authors declare no competing interests.Ethics Approval Statement: All participants provided informed consent for the survey and ethics approval was received from the research ethics boards of the Université de Montréal and the Centre Hospitalier Universitaire Sainte-Justine.

Multicenter cohort study of multisystem inflammatory syndrome in children (MIS-C) (preprint)

BACKGROUND SARS-CoV-2 infection can lead to multisystem inflammatory syndrome in children (MIS-C). We investigated risk factors for severe disease and explored changes in severity over time. METHODS Children up to 17 years of age admitted March 1, 2020 through March 7 th , 2021 to 15 hospitals in Canada, Iran and Costa Rica with confirmed or probable MIS-C were included. Descriptive analysis and comparison by diagnostic criteria, country, and admission date was performed. Adjusted absolute average risks (AR) and risk differences (RD) were estimated for characteristics associated with ICU admission or cardiac involvement. RESULTS Of 232 cases (106 confirmed) with median age 5.8 years, 56% were male, and 22% had comorbidities. ICU admission occurred in 73 (31%) but none died. Median length of stay was 6 days (inter-quartile range 4-9). Children 6 to 12 years old had the highest AR for ICU admission (44%; 95% confidence interval [CI] 34-53). Initial ferritin greater than 500 mcg/L was associated with ICU admission. When comparing cases admitted up to October 31, 2020 to those admitted later, the AR for ICU admission increased from 25% (CI 17-33) to 37% (CI 29-46) and for cardiac involvement from 44% (CI 35-53) to 75% (CI 66-84). Risk estimates for ICU admission in the Canadian cohort demonstrated a higher risk in December 2020-March 2021 compared to March-May 2020 (RD 25%; 95%CI 7-44). INTERPRETATION MIS-C occurred primarily in previously well children. Illness severity appeared to increase over time. Despite a high ICU admission incidence, most children were discharged within one week.

Neurological Manifestations of SARS-CoV-2 in Hospitalized Children: A Multi-National Cohort Study (preprint)

Background: Knowledge about neurological manifestations of SARS-CoV-2 in children is limited. We describe neurological manifestations in an international cohort of hospitalized pediatric patients.Methods: This is a multi-national observational study involving tertiary healthcare institutions in Canada, Costa Rica and Iran. We included patients 1 day-18 years admitted for any medical reason February 1, 2020-January 31, 2021 with laboratory evidence of SARS-CoV-2 infection by RT-PCR or serological testing. Descriptive analyses and logistic regression were performed where appropriate using JASP version 0⋅13.Findings: 298 hospitalized children with confirmed SARS-CoV-2 infection (median age 3⋅9 years [IQR 0⋅6-10⋅1]) from Canada (n=152), Costa Rica (n=115) and Iran (n=31) were included. Fifty-one (17%) had neurological manifestations, of which headache (73%), seizures (23%) and altered mental status (6%) were most frequently seen. Children with neurological symptoms had equivalent rates of comorbidities overall but were more likely to have underlying chronic neurological conditions. Additionally, those with neurological symptoms were more likely to be admitted to the ICU (15/51 [29%] vs. 32/247 [13%]; p =0⋅0033) and had longer length of hospital stay (6 days [IQR 3-8] vs. 4 days [IQR 2-7]; p =0⋅0060). Abnormalities were found in all children with neurological manifestations who received neuroimaging (n=6). Neurological manifestations were seen in 19% of the Iranian cohort, 23% of the Costa Rican cohort, and 12% of the Canadian cohort. Country of residence Costa Rica (adjusted OR: 2⋅520, 95% CI: 1⋅325-4⋅791, p =0⋅005), ICU admission (adjusted OR: 2⋅678, 95% CI: 1⋅307-5⋅486, p =0⋅007) and number of acute SARS-CoV-2 infection symptoms (adjusted OR: 1⋅355, 95% CI: 1⋅232-1⋅491, p <0⋅0001) were independently associated with neurological manifestations using multivariate analysis.Interpretation: We show that children with underlying comorbidities, especially underlying neurological diagnoses, are more likely to develop neurological complications of SARS CoV-2, and that sociodemographic factors, such as country of residence associate with varying rates of neurological manifestations. Future studies should focus on long-term outcomes in these children.Funding Statement: There was no funding source for this study.Declaration of Interests: Unrelated to this work, E.A. Yeh has received research funding from NMSS, CMSC, CIHR, NIH, OIRM, SCN, CBMH Chase an Idea, SickKids Foundation, Rare Diseases Foundation, MS Scientific Foundation (Canada), McLaughlin Centre, Mario Battaglia Foundation. Investigator initiated research funding from Biogen. Scientific advisory: Biogen, Hoffman-LaRoche, Vielabio. Speaker honoraria: Saudi Epilepsy Society, NYU, MS-ATL; ACRS, PRIME. J. Papenburg holds a “Chercheur-boursier clinicien” career award from the Fonds de recherche du Québec – Santé (FRQS) and reports grants from MedImmune, grants from Sanofi Pasteur, personal fees from Seegene, grants and personal fees from AbbVie, outside the submitted work. All other authors declare no conflict of interest.Ethics Approval Statement: All clinical and laboratory investigations were performed according to institutional protocols. Informed consent and ethics approval were obtained following requirements of the research ethics board of each participating institution.

Seroprevalence of anti-SARS-CoV-2 antibodies among school and daycare children and personnel: Protocol for a cohort study in Montreal, Canada (preprint)

Background: Further evidence is needed to understand the contribution of schools and daycares to the spread of COVID-19 in the context of diverse transmission dynamics and continually evolving public health interventions. The Enfants et COVID-19: Etude de seroprevalence (EnCORE) study will estimate the seroprevalence and seroconversion of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among school and daycare children and personnel. In addition, the study will examine associations between seroprevalence and socio-demographic characteristics and reported COVID-19 symptoms and tests, and investigates changes in health, lifestyle and well-being outcomes. Methods: This study includes children and personnel from 62 schools and daycares in four neighbourhoods in Montreal, Canada. All children age 2-17 years attending one of the participating schools or daycares and their parents are invited to participate, as well as a sample of personnel members. Participants respond to brief questionnaires and provide blood samples, collected via dried blood spot (DBS), at baseline (October 2020-March 2021) and follow-up (May-June 2021). Questionnaires include socio-demographic and household characteristics, reported COVID-19 symptoms and tests, potential COVID-19 risk factors and prevention efforts, and health and lifestyle information. Logistic regression using generalized estimating equations will be used to estimate seroprevalence and seroconversion, accounting for school-level clustering. Discussion: The results of the EnCORE study will contribute to our knowledge about SARS-CoV-2 transmission in schools and daycares, which is critical for decisions regarding school attendance and the management of school outbreaks through the remainder of this school year and beyond. Keywords SARS-CoV-2; COVID-19; Children; School; Serology; Protocol; Canada

Dried blood spot specimens for SARS-CoV-2 antibody testing: A multi-site, multi-assay comparison (preprint)

The true severity of infection due to COVID-19 is under-represented because it is based on only those who are tested. Although nucleic acid amplifications tests (NAAT) are the gold standard for COVID-19 diagnostic testing, serological assays provide better population-level SARS-CoV-2 prevalence estimates. Implementing large sero-surveys present several logistical challenges within Canada due its unique geography including rural and remote communities. Dried blood spot (DBS) sampling is a practical solution but comparative performance data on SARS-CoV-2 serological tests using DBS is currently lacking. Here we present test performance data from a well-characterized SARS-CoV-2 DBS panel sent to laboratories across Canada representing 10 commercial and 2 in-house developed tests for SARS-CoV-2 antibodies. Three commercial assays identified all positive and negative DBS correctly corresponding to a sensitivity, specificity, positive predictive value, and negative predictive value of 100% (95% CI = 72.2, 100). Two in-house assays also performed equally well. In contrast, several commercial assays could not achieve a sensitivity greater than 40% or a negative predictive value greater than 60%. Our findings represent the foundation for future validation studies on DBS specimens that will play a central role in strengthening Canada’s public health policy in response to COVID-19.

Multicenter cohort study of children hospitalized with SARS-CoV-2 infection (preprint)

Background: A cohort study was conducted to describe and compare the burden and characteristics of SARS-CoV-2 infection in hospitalized children in three countries. Methods: This was a retrospective cohort of consecutive children admitted to 15 hospitals (13 in Canada and one each in Iran and Costa Rica) up to November 16, 2020. Cases were included if they had SARS-CoV-2 infection or multi-system inflammatory syndrome in children (MIS-C) with molecular detection of SARS-CoV-2 or positive SARS-CoV-2 serology. Results: Of 211 included cases (Canada N=95; Costa Rica N=84; Iran N=32), 103 (49%) had a presumptive diagnosis of COVID-19 or MIS-C at admission while 108 (51%) were admitted with other diagnoses. Twenty-one (10%) of 211 met criteria for MIS-C. Eighty-seven (41%) had comorbidities. Children admitted in Canada were older than those admitted to non-Canadian sites (median 4.1 versus 2.2 years; p<0.001) and less likely to require mechanical ventilation (3/95 [3%] versus 15/116 [13%]; p<0.05). Requirement for oxygen or ICU occurred in 64 (30%) and death in four, three of whom. had malignancies. Age < 30 days, admission outside of Canada, presence of at least one comorbidity and chest imaging compatible with COVID-19 predicted severe disease. Conclusions: Approximately half of hospitalized children with confirmed SARS-CoV-2 infection or MIS-C were admitted with other suspected diagnoses. Disease was more severe at non-Canadian sites. Neonates, children with comorbidities and those with chest radiographs compatible with COVID-19 were at increased risk for severe disease.

Evaluation of a Commercial Culture-free Neutralization Antibody Detection Kit for Severe Acute Respiratory Syndrome-Related Coronavirus-2 and Comparison with an Anti-RBD ELISA Assay (preprint)

BackgroundSARS-CoV-2 surrogate neutralization assays that obviate the need for viral culture offer substantial advantages regarding throughput and cost. The cPass SARS-CoV-2 Neutralization Antibody Detection Kit (Genscript) is the first such commercially available assay, detecting antibodies that block RBD/ACE-2 interaction. We aimed to evaluate cPass to inform its use and assess its added value compared to anti-RBD ELISA assays. MethodsSerum reference panels comprising 205 specimens were used to compare cPass to plaque-reduction neutralization test (PRNT) and a pseudotyped lentiviral neutralization (PLV) assay for detection of neutralizing antibodies. We assessed the correlation of cPass with an ELISA detecting anti-RBD IgG, IgM, and IgA antibodies at a single timepoint and across intervals from onset of symptoms of SARS-CoV-2 infection. ResultsCompared to PRNT-50, cPass sensitivity ranged from 77% - 100% and specificity was 95% - 100%. Sensitivity was also high compared to the pseudotyped lentiviral neutralization assay (93% [95%CI 85-97]), but specificity was lower (58% [95%CI 48-67]). Highest agreement between cPass and ELISA was for anti-RBD IgG (r=0.823). Against the pseudotyped lentiviral neutralization assay, anti-RBD IgG sensitivity (99% [95%CI 94-100]) was very similar to that of cPass, but overall specificity was lower (37% [95%CI 28-47]). Against PRNT-50, results of cPass and anti-RBD IgG were nearly identical. ConclusionsThe added value of cPass compared to an IgG anti-RBD ELISA was modest.

Global seroprevalence of SARS-CoV-2 antibodies: a systematic review and meta-analysis (preprint)

BackgroundStudies reporting estimates of the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies have rapidly emerged. We aimed to synthesize seroprevalence data to better estimate the burden of SARS-CoV-2 infection, identify high-risk groups, and inform public health decision making. MethodsIn this systematic review and meta-analysis, we searched publication databases, preprint servers, and grey literature sources for seroepidemiological study reports, from January 1, 2020 to August 28, 2020. We included studies that reported a sample size, study date, location, and seroprevalence estimate. Estimates were corrected for imperfect test accuracy with Bayesian measurement error models. We conducted meta-analysis to identify demographic differences in the prevalence of SARS-CoV-2 antibodies, and meta-regression to identify study-level factors associated with seroprevalence. We compared region-specific seroprevalence data to confirmed cumulative incidence. PROSPERO: CRD42020183634. FindingsWe identified 338 seroprevalence studies including 2.3 million participants in 50 countries. Seroprevalence was low in the general population (median 3.2%, IQR 1.0-6.4%) and slightly higher in at-risk populations (median 5.4%, IQR 1.5-18.4%). Median seroprevalence varied by WHO Global Burden of Disease region (p < 0.01), from 1.0% in Southeast Asia, East Asia and Oceania to 18.8% in South Asia. National studies had lower seroprevalence estimates than local (p = 0.02) studies. Compared to White persons, Black persons (prevalence ratio [RR] 2.34, 95% CI 1.60-3.43) and Asian persons (RR 1.56, 95% CI 1.22-2.01) were more likely to be seropositive. Seroprevalence was higher among people ages 18-64 compared to 65 and over (RR 1.26, 95% CI 1.04-1.52). Health care workers had a 1.74x (95% CI: 1.18-2.58) higher risk compared to the general population. There was no difference in seroprevalence between sexes. There were 123 studies (36%) at low or moderate risk of bias. Seroprevalence estimates from national studies were median 11.9 (IQR 8.0 - 16.6) times higher than the corresponding SARS-CoV-2 cumulative incidence. InterpretationMost of the population remains susceptible to SARS-CoV-2 infection. Public health measures must be improved to protect disproportionately affected groups, including non-White people and adults. Measures taken in SE Asia, E Asia and Oceania, and Latin America and Caribbean may have been more effective in controlling virus transmission than measures taken in other regions. FundingPublic Health Agency of Canada through the COVID-19 Immunity Task Force.

Sequential ER stress and inflammatory responses are induced by SARS-CoV-2 ORF3 through ERphagy (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have resulted in a number of severe cases of COVID-19 and deaths worldwide. However, knowledge of SARS-CoV-2 infection, diseases and therapy remains limited, underlining the urgency of fundamental studies and drug development. Studies have shown that induction of autophagy and hijacking of autophagic machinery are essential for infection and replication of SARS-CoV-2; however, the mechanism of this manipulation and function of autophagy during SARS-CoV-2 infection remain unclear. In the present study, we identified ORF3 as an inducer of autophagy and revealed that ORF3 localizes to the ER and induces FAM134B-related ERphagy through the HMGB1-Beclin1 pathway. As a consequence, ORF3 induces ER stress and inflammatory responses through ERphagy and sensitizes cells to ER stress-induced cell death, suggesting that SARS-CoV-2 ORF3 hijacks ERphagy and then harms ER homeostasis to induce inflammatory responses through excessive ER stress. These findings reveal a sequential induction of ERphagy, ER stress and acute inflammatory responses during SARS-CoV-2 infection and provide therapeutic potential for ERphagy and ER stress-related drugs for COVID-19 treatment and prevention. ImportanceSARS-CoV-2 infection and replication require autophagosome-like double-membrane vacuoles. Inhibition of autophagy suppresses viral replication, indicating the essential role of autophagy in SARS-CoV-2 infection. However, how SARS-CoV-2 hijacks autophagy and the function of autophagy in the disease progression remain unknown. Here, we reveal that SARS-CoV-2 ORF3 induces ERphagy and consequently induces ER stress to trigger acute inflammatory responses and enhance sensitivity to ER stress-induced apoptosis. Our studies uncover ERphagy-induced inflammatory responses during SARS-CoV-2 infection and provide a promising therapeutic approach for treating SARS-CoV-2 infection and inflammatory responses in COVID-19 by manipulating autophagy and ER stress.