Project 459240

With mass vaccination campaigns underway across Canada for 12 years and older, the pandemic has been dramatically altered although important challenges remain. The EnCORE study is a seroprevalence study in schools and daycares in Montreal with funding until December 31, 2021. We propose to continue EnCORE's core work of seroprevalence monitoring while incorporating immune response measures for a subset of participants. We will continue following EnCORE study participants (n=2,061) for two additional rounds of data collection. The data collection will involve an online questionnaire followed by in-home finger prick blood collection. The blood samples will be analyzed in a laboratory for natural and vaccine-induced immunoglobin G (IgG). Also, we will randomly select 90 participants from 5 to 11 years of age for venous blood draws to further explore cell-mediated immunity (e.g., total antibody levels, neutralization, and T-cell testing). Multivariable statistical analyses will be conducted to estimate the number of children with SARS-CoV-2 antibodies, vaccine coverage, and magnitude of antibody response. This work will positively contribute to existing COVID-19 research gaps. The seroprevalence estimates will provide a better understanding of the disease dynamics, to identify hotspots and at-risk groups for targeted interventions, until high coverage of COVID-19 vaccination is obtained in children and in teenagers. Furthermore, having a better understanding of cell-medicated immunity and the potential role of prior immunity to human common coronaviruses, will be a valuable contribution to COVID-19 immunology, understanding of vaccine responses, need for booster shots, number of doses needed in children, and potentially an explanation of why children are less likely to be seriously sick with COVID-19.