Pediatric Influenza Vaccine Effectiveness Against Emergency Visits and Hospitalization in Canada: 2024-2025 and 2025-2026 seasons
- 1ICES
Abstract
Importance: Influenza causes substantial morbidity in children, yet Canadian data on influenza vaccine effectiveness (VE) in preventing emergency department (ED) visits and hospitalizations are limited. Objective: To estimate VE against influenza-associated ED visits and hospitalizations among children during the 2024-2025 and 2025-2026 seasons. Design: Test negative case control design. Setting: Fourteen Canadian pediatric tertiary-care hospitals participating in the Surveillance Program for the Rapid IdeNtification and TracKing of Infectious Diseases in kidS (SPRINT KIDS) network. Participants: Symptomatic children aged 6 months to <18 years tested for influenza from October 27, 2024, to June 7, 2025, and from November 2, 2025, to June 13, 2026. Exposure: At least one dose of current season influenza vaccine. Main Outcomes and Measures: VE against laboratory confirmed influenza A or B associated with an ED visit or hospitalization. VE was estimated using multivariable logistic regression adjusted for age, epidemiologic week, site, and high-risk comorbidity. Results: The 2024/2025 season included 17,316 encounters (median [IQR] age=41.0 [18.5, 82.3] months; 54.0% male), with 4,760 influenza-positive cases (8.9% vaccinated) and 12,556 influenza-negative controls (15.9% vaccinated). The 2025/2026 season included 13,417 encounters (median [IQR] age=33.5 [16.7, 74.8] months; 54.1% male), with 4,798 cases (7.6% vaccinated) and 8,619 controls (18.1% vaccinated). VE against any influenza was 47% (95%CI, 40%, 53%) and 53% (95%CI, 46%, 59%) in 2024/2025 and 2025/2026, respectively. VE against ED visits was 53% (95%CI, 45%, 59%) and 57% (95%CI, 49%, 63%), and VE against hospitalization was 33% (95%CI, 16%, 47%) and 48% (95%CI, 33%, 59%) in 2024/2025 and 2025/2026, respectively. VE was lower against influenza A as compared to B in both seasons: 31% (95%CI, 22%, 39%) vs. 75% (95%CI, 64%, 82%) (p<0.001) in 2024-2025; and 42% (95%CI, 32%, 50%) vs. 64% (95%CI, 55%, 72%) (p=0.001) in 2025/2026. VE was lower in children aged 10 to <18 years than in those <10 years, particularly among children with comorbidities. Protection against influenza A lasted up to 90 days, whereas it persisted beyond 120 days for influenza B. Conclusions and Relevance: Influenza vaccines were moderately effective against pediatric ED visits and hospitalizations in both seasons. Routine vaccination should continue to be recommended to prevent hospital-attended influenza.
Related
- A Bayesian Re-analysis of the GALFLU Trial of High-Dose vs Standard-Dose Influenza Vaccine Against Hospitalization Outcomes
- An LLM enabled real-time estimation of seasonal influenza vaccine effectiveness from social media data
- 2025/26 subclade-specific influenza A and B vaccine effectiveness estimates and discordant laboratory-based indicators of vaccine match or mismatch
- Potential impact of changes in influenza vaccination coverage and effectiveness on pediatric influenza burden in the United States, 2022/23-2024/25
- Effectiveness of nirsevimab against hospitalization for RSV bronchiolitis according to RSV lineages
BibTeX
@misc{kwong2026pediatric,
title = {{Pediatric Influenza Vaccine Effectiveness Against Emergency Visits and Hospitalization in Canada: 2024-2025 and 2025-2026 seasons}},
author = {J. C. Kwong and D. M. Goldfarb and M. Bhatt and J. Xie and S. A. Buchan and J. Papenburg and J. Cheng and M. Eltorki and Y. Finkelstein and V. Sabhaney and J. M. Pernica and J. Gravel and A. Kam and S. Berthelot and B. Burstein and J. Emsley and A. Mater and S. Ali and A. Shah and N. Poonai and D. Beer and P. Gill and J. Dickinson and S. Freedman},
howpublished = {medRxiv},
year = {2026},
month = nov,
doi = {10.64898/2026.11.03.26367131},
url = {https://www.medrxiv.org/content/10.64898/2026.11.03.26367131v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Pediatric Influenza Vaccine Effectiveness Against Emergency Visits and Hospitalization in Canada: 2024-2025 and 2025-2026 seasons
AU - J. C. Kwong
AU - D. M. Goldfarb
AU - M. Bhatt
AU - J. Xie
AU - S. A. Buchan
AU - J. Papenburg
AU - J. Cheng
AU - M. Eltorki
AU - Y. Finkelstein
AU - V. Sabhaney
AU - J. M. Pernica
AU - J. Gravel
AU - A. Kam
AU - S. Berthelot
AU - B. Burstein
AU - J. Emsley
AU - A. Mater
AU - S. Ali
AU - A. Shah
AU - N. Poonai
AU - D. Beer
AU - P. Gill
AU - J. Dickinson
AU - S. Freedman
PY - 2026
DA - 2026/11/03
PB - medRxiv
DO - 10.64898/2026.11.03.26367131
UR - https://www.medrxiv.org/content/10.64898/2026.11.03.26367131v1
AB - Importance: Influenza causes substantial morbidity in children, yet Canadian data on influenza vaccine effectiveness (VE) in preventing emergency department (ED) visits and hospitalizations are limited. Objective: To estimate VE against influenza-associated ED visits and hospitalizations among children during the 2024-2025 and 2025-2026 seasons. Design: Test negative case control design. Setting: Fourteen Canadian pediatric tertiary-care hospitals participating in the Surveillance Program for the Rapid IdeNtification and TracKing of Infectious Diseases in kidS (SPRINT KIDS) network. Participants: Symptomatic children aged 6 months to <18 years tested for influenza from October 27, 2024, to June 7, 2025, and from November 2, 2025, to June 13, 2026. Exposure: At least one dose of current season influenza vaccine. Main Outcomes and Measures: VE against laboratory confirmed influenza A or B associated with an ED visit or hospitalization. VE was estimated using multivariable logistic regression adjusted for age, epidemiologic week, site, and high-risk comorbidity. Results: The 2024/2025 season included 17,316 encounters (median [IQR] age=41.0 [18.5, 82.3] months; 54.0% male), with 4,760 influenza-positive cases (8.9% vaccinated) and 12,556 influenza-negative controls (15.9% vaccinated). The 2025/2026 season included 13,417 encounters (median [IQR] age=33.5 [16.7, 74.8] months; 54.1% male), with 4,798 cases (7.6% vaccinated) and 8,619 controls (18.1% vaccinated). VE against any influenza was 47% (95%CI, 40%, 53%) and 53% (95%CI, 46%, 59%) in 2024/2025 and 2025/2026, respectively. VE against ED visits was 53% (95%CI, 45%, 59%) and 57% (95%CI, 49%, 63%), and VE against hospitalization was 33% (95%CI, 16%, 47%) and 48% (95%CI, 33%, 59%) in 2024/2025 and 2025/2026, respectively. VE was lower against influenza A as compared to B in both seasons: 31% (95%CI, 22%, 39%) vs. 75% (95%CI, 64%, 82%) (p<0.001) in 2024-2025; and 42% (95%CI, 32%, 50%) vs. 64% (95%CI, 55%, 72%) (p=0.001) in 2025/2026. VE was lower in children aged 10 to <18 years than in those <10 years, particularly among children with comorbidities. Protection against influenza A lasted up to 90 days, whereas it persisted beyond 120 days for influenza B. Conclusions and Relevance: Influenza vaccines were moderately effective against pediatric ED visits and hospitalizations in both seasons. Routine vaccination should continue to be recommended to prevent hospital-attended influenza.
ER -