The CHILD Cohort COVID-19 Add-On Study

Weekly Symptom check (by text message) Brief survey will capture COVID-19 signs and symptoms, testing and results, and healthcare utilization. Questions will be aligned with the Government of Canada self-assessment tool and harmonized with international partners

Quarterly CoRonavIruS Health Impact Survey (CRISIS) (7) and body weight: The 10-minute CRISIS survey captures COVID-19 exposure, life changes due to the COVID-19 crisis, daily behaviours, emotions and worries, media use and substance use. Each household member will complete the survey; parents will complete on behalf of younger children. Body weight (measured at home) will also be reported.

Quarterly CoRonavIruS Health Impact Survey (CRISIS) (7) and body weight: The 10-minute CRISIS survey captures COVID-19 exposure, life changes due to the COVID-19 crisis, daily behaviours, emotions and worries, media use and substance use. Each household member will complete the survey; parents will complete on behalf of younger children. Body weight (measured at home) will also be reported.

Analysis of recently-collected pre-pandemic bio-samples: To determine the pre-pandemic immune profile of CHILD index children, we will analyze a subset including all cases (asymptomatic and symptomatic) detected by serology and symptom surveys, plus a random subset of uninfected controls (estimated: 400 children in total). The investigators will assess: a) a panel of innate and adaptive cytokines and chemokines using a commercial multiplex assay, b) immune cell phenotypes using high dimensional flow cytometry and c) viral antibodies to establish prior/recent infections and cross-reactivity using targeted ELISA assays developed for antibodies to other human beta-coronaviruses

Prevalence and severity of infection will be estimated in real-time from weekly reports, and confirmed from serology testing. Severity will be classified as asymptomatic, mild or severe using WHO criteria. Transmission will be assessed using a multilevel modeling approach by province, house, and individual. Persistence of potential immunity will be determined from longitudinal serology testing for SARS-CoV-2 antibodies.

In addition to the new data generated by this grant, the investigators will access existing data from the CHILD database, which contains over 50 million data points including multi-omics measurements from biological samples; indoor exposures including tobacco smoke; longitudinal clinical data on cardiometabolic and respiratory health, anthropometrics and body composition; mental health and psychosocial data; health behaviour data including sleep, physical activity, screen time and diet; and socioeconomic data including ethnicity. CHILD data is also integrated with www.CANUE.ca environmental data including weather, air quality and population density data. The investigators will use two approaches to analyze these data: hypothesis-driven and unbiased machine learning.

The investigators will identify individuals experiencing a decline in mental or physical health during the pandemic (not due to infection) and identify families and individuals experiencing food insecurity, financial difficulties, domestic violence and substance abuse. The investigators will report the prevalence of these outcomes to our knowledge users monthly. The investigators will use hypothesis-driven and unbiased approaches to identify factors that may predict risk for - or resilience against - these negative impacts of the pandemic. The investigators will also investigate socioeconomic inequities.

Sex differences in COVID-19 severity have been reported in adults (8) and gendered health behaviours are relevant to exposure and transmission. Mental health effects may also vary by sex and gender. It is not known if these differences exist in children, and how they might affect asymptomatic infection and transmission. The investigators will disaggregate all analyses by sex and/or gender in order to address these issues.