Reducing SARS-CoV-2 risk in children: Understanding the role of vaccination and public health measures

Dr. Jonathon Maguire is an Associate Professor of Pediatrics and Nutritional Sciences at the University of Toronto, a Scientist at the Centre for Urban Health Solutions at the Li Ka Shing Knowledge Institute of St. Michael’s Hospital, and a member of the Edwin S.H. Leong Centre for Healthy Children. In this update, he provides insights into his research on reducing SARS-CoV-2 risks in children.

The COVID-19 pandemic placed children and families in a unique position, requiring them to balance the risks of infection with the need for normal social and educational development. While much of early pandemic research focused on adults, understanding the effectiveness of public health measures in children remains an important research priority. This project seeks to evaluate how both pharmaceutical and non-pharmaceutical interventions (NPIs) influence SARS-CoV-2 infection rates in children.

Our work includes two major studies that have provided key insights into vaccine effectiveness and seroprevalence among children. The first examined the seroprevalence of SARS-CoV-2 antibodies in children receiving primary care in Toronto. Through TARGet Kids!, Canada’s largest primary care research network for children this study tracked the presence of both infection-acquired and vaccine-acquired antibodies, revealing a rise in infection-acquired seroprevalence from 2.6% in early 2021 to 50.7% by late 2022. Meanwhile, vaccine-acquired antibodies reached 45.2% by late 2022, demonstrating the growing role of vaccination in this population. These findings, published in the Canadian Journal of Public Health, contribute to our understanding of community transmission dynamics and the evolving immunity landscape in children.

The second study assessed the real-world effectiveness of the mRNA-1273 (Moderna) vaccine in children aged 6 months to 5 years. Using a test-negative design with linked health administrative data from ICES, we found that two doses of mRNA-1273 provided 90% protection against symptomatic infection and 82% effectiveness against COVID-19-related hospitalization. These findings, recently published in Open Forum Infectious Diseases, provide evidence for vaccination policy in young children, a population for whom data on vaccine effectiveness have been limited.

While the focus of our work began with vaccination, non-pharmaceutical interventions (NPIs) such as masking, physical distancing, and staying home have also played an important role in reducing transmission. However, there remains limited data on their specific impact in pediatric populations. Our next phase of research aims to fill this gap by analyzing how adherence to NPIs affects infection risk in children. We are currently working on TARGet Kids! linked datasets at ICES to study the relationship between NPIs and infection rates. This research will provide essential insights into the effectiveness of individual and layered interventions in preventing SARS-CoV-2 transmission.

A key strength of this project is its meaningful engagement with children and families through the TARGet Kids! Parent and Caregiver Team, a parent partnership which prioritizes co-design and community involvement. This partnership fosters shared decision-making, enhancing the feasibility, relevance, and impact of our research. By embedding parent and caregiver perspectives throughout the research process, we ensure that interventions are not only effective but also practical and acceptable within real-world family contexts. 

Understanding the role of vaccines and non-pharmaceutical public health measures in reducing SARS-CoV-2 infection in children is important for shaping future pandemic policies. Our research continues to generate evidence that will inform vaccine recommendations, public health guidelines, and broader dialog on how best to protect children during pandemic periods while minimizing disruptions to their health and well-being.