Safety of COVID-19 and influenza vaccines in children and adolescents with immunocompromised or autoimmune conditions: Findings from the Canadian National Vaccine Safety (CANVAS) network.

Safety data on COVID-19 and influenza vaccination in immunocompromised and/or autoimmune pediatric populations remains limited. This study evaluated post-vaccination health events in this vulnerable population using active surveillance data from the Canadian National Vaccine Safety (CANVAS) Network. A prospective cohort of participants aged 6 months to 19 y, who self-identified with an autoimmune and/or immunocompromised condition, were followed across several Canadian provinces (2023-2025). Participants were vaccinated with COVID-19 only, seasonal influenza vaccine only, or had both vaccines co-administered and reported new or worsening health events within 7 d post-vaccination; unvaccinated participants reported new or worsening events in the prior week. Health events were defined as events resulting in school/daycare absenteeism, prevention of daily activities, or requiring medical consultation. Symptoms were collected in a structured survey. Associations between vaccination and health events were assessed using multivariable logistic regression, adjusting for demographics and health factors. Of 868 participants with autoimmune and/or immunocompromised conditions, 474 were vaccinated and 394 were unvaccinated controls. In the co-administered COVID-19 and influenza vaccine group, there was no significant increase in health events (aOR 0.83; 95% CI 0.47-1.46) compared to unvaccinated controls. The COVID-19-only and influenza-only subgroups were underpowered to detect meaningful associations. Co-administered COVID-19 and influenza vaccination was not associated with an increased risk of health events in children and adolescents with autoimmune and/or immunocompromised conditions, supporting vaccine safety in this population.