ABSTRACT
BACKGROUND: Public health preventive measures have been a necessary intervention in preventing COVID-19 transmission. OBJECTIVE(S): The objectives of this study were 1) To investigate how the adherence to COVID-19 public health measures among parents and children in Ontario changed over time;2) To determine if provincial lockdowns were associated with higher adherence to public health measures among parents;3) To determine if school closures were associated with higher adherence to public health measures among children. DESIGN/METHODS: A longitudinal study was conducted in children aged 0-10 years and their parents through the TARGet Kids! COVID-19 Study of Children and Families in the Greater Toronto Area, Canada (April 2020 -May 2021). Parents completed weekly questionnaires on sociodemographics and public health practices. The primary exposure was calendar date. Secondary exposures were provincial lockdowns and school closures. The primary outcome was adherence to public health preventive measures (staying home, limiting visitors in the home, avoiding contact with others, socially distancing, and handwashing, measured as number of days practicing per week) measured separately for parents and children. Linear mixed effects regression and piecewise linear splines mixed effects models were conducted. RESULT(S): 819 children and their parents contributed 13,220 observations to the study over 13 months. Mean age was 5.6 years (SD=2.7) and 373 were female (45.5%). 273 children (35.1%) had a parent who worked as an essential worker and 254 (35.4%) of families lived in a COVID-19 'hotspot'. The number of days per week that parents adhered to all 5 public health measures decreased by 0.029 days (p<0.001), and by 0.146 days for children (p<0.001) over the study duration. For parents, adherence to the five public health measures decreased over time during the first lockdown (beta=- 0.06, p<0.001) and first reopening (beta=-0.01, p<0.001), but increased again during the second lockdown (beta=0.01, p<0.001). For children, adherence to the five public health measures decreased over time during the first school closure, increased during the second closure, and decreased during second reopening (beta=-0.04, p<0.01). See Figure 1. CONCLUSION(S): Parents and children both decreased in their adherence to social distancing, staying at home, and avoiding contact with others over time. Lockdown after a period of reopening increased parent adherence to public health measures and school closures increased adherence in children. Supports may be necessary to help children and parents maintain adherence to public measures over prolonged periods of lockdown and school closure. .
ABSTRACT
Background/Case Studies: Multiple assays to detect SARS-COV-2 antibodies are available but no gold standard exists. Due to many factors including waning antibodies and differences in test designs, discordance between SARS-CoV-2 serology assays is common. Given these limitations we used multiple assays and methodological approaches to estimate SARS-COV-2 seroprevalence during the first COVID-19 wave in Canada. Study Design/Methods: This serial cross-sectional study was conducted using residual plasma from healthy blood donors between April-September 2020. Qualitative (Table Presented) assessment of SARS-CoV-2 IgG antibodies was based on four assays: Abbott Architect SARS-Cov-2 IgG assay (target nucleocapsid) (Abbott-NP) and three in-house IgG ELISA assays (target spike glycoprotein (Spike), spike receptor binding domain (RBD), and nucleocapsid (NP)) based on thresholds set by the manufacture or 3-standarddeviations from the negative mean. We compared seroprevalence rates by multiple composite reference standards (CRS) and by a series of Bayesian Latent Class Models (BLCM) (using uninformative, weakly and informative priors). Using the BLCM we estimated assay characteristics, bimonthly to evaluate changes over time. Results/Findings: In total, 8999 blood samples were tested. The Abbott-NP assay consistently estimated seroprevalence to be lower than the ELISA-based assays. A priori, choosing a combination of 2 assays resulted in a range of seroprevalence estimates that ranged from 0.2% to 0.5% in April to 0.4% to 1.5% in September. From 16 possible diagnostic phenotypes, 13 were observed, only 33 samples (0.4%) were positive by all four assays. BLCM with non-informative priors provided the best model fit and predicted seroprevalence increased from 0.7% (95% CrI;0.6, 0.8%) in April/May to 1.0% (0.8, 1.1%) in June/ July to 1.5% (1.3, 1.8) in August/September. Assay characteristics varied considerably over time. Overall RBD had the highest sensitivity 82.2% (69.3, 92.9%) with a specificity of 99.6% (99.4, 99.7%). In contrast the sensitivity of the Abbott-NP assay was the lowest and waned from 63.2% (41.4, 83.1%) in April/May to 33.9% (19.7, 53.1%) by August/September. Conclusions: Regardless of the analytical method we found at the end of the first COVID-19 wave, SARSCoV- 2 seroprevalence among a healthy population of blood donors was low (<2%). While the sensitivity of all assays waned, the rates did vary. We found significant limitations to using a single assay to estimate SARSCoV- 2 seroprevalence in a low prevalence setting, such as healthy Canadian blood donors during the first wave of the COVID-19 pandemic.
ABSTRACT
Background: Severe acute respiratory syndrome virus 2 (SARS-CoV-2), likely a bat-origin coronavirus, spilled over from wildlife to humans in China in late 2019, manifesting as a respiratory disease. Coronavirus disease 2019 (COVID-19) spread initially within China and then globally, resulting in a pandemic.