Clinical outcomes during the 2025-2026 and 2024-2025 influenza seasons in a US EHR network: an ecological comparison during A(H3N2) subclade K predominance.
- 1Department of Pediatrics, Nara Prefecture General Medical Center, Nara, Japan.
- 2AMR Clinical Reference Center, Japan Institute for Health Security, Tokyo, Japan.
Abstract
Objectives
The influenza A(H3N2) subclade K virus has predominated in the 2025-2026 season. This study compared the clinical severity of influenza between 2025-2026 and 2024-2025 seasons.Methods
In this retrospective cohort study, a multicenter electronic health record database (TriNetX) was used. The clinical outcomes after influenza infection confirmed by nucleic acid detection were ecologically compared between the 2025-2026 and 2024-2025 seasons with propensity score matching.Results
There were 8965 and 8937 children and 7488 and 6947 adults with confirmed influenza A(H3N2) infection in the 2025-2026 and 2024-2025 seasons, respectively. After each propensity score matching, the odds ratios for children and adults were not assessed (due to the small number of events) and 0.87 (95% confidence interval 0.71-1.05), P = 0.148 for death; 1.32 (1.10-1.59), P = 0.003 and 0.91 (0.82-1.02), P = 0.092 for critical care admission; 1.06 (0.97-1.16), P = 0.191 and 1.01 (0.94-1.08), P = 0.803 for hospitalization; 0.88 (0.73-1.07), P = 0.197 and 0.93 (0.83-1.04), P = 0.194 for mechanical ventilation; and 1.10 (0.91-1.32), P = 0.320 and 0.93 (0.83-1.03), P = 0.177 for vasopressor use, respectively.Conclusion
In this electronic health record-based season-level comparison, no consistent adjusted differences were observed; however, the study could not directly assess subclade K-specific severity or rule out clinically relevant differences. Rapid and timely monitoring of clinical characteristics and severity in the case of an emerging influenza strain or subclade is important to guide preventive and therapeutic strategies against influenza.
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BibTeX
@article{kitano2026clinical,
title = {{Clinical outcomes during the 2025-2026 and 2024-2025 influenza seasons in a US EHR network: an ecological comparison during A(H3N2) subclade K predominance.}},
author = {Taito Kitano and Sayaka Yoshida},
journal = {IJID regions},
year = {2026},
month = sep,
doi = {10.1016/j.ijregi.2026.101025},
url = {https://europepmc.org/article/MED/42921464},
note = {CC BY},
}
RIS
TY - JOUR
TI - Clinical outcomes during the 2025-2026 and 2024-2025 influenza seasons in a US EHR network: an ecological comparison during A(H3N2) subclade K predominance.
AU - Taito Kitano
AU - Sayaka Yoshida
PY - 2026
DA - 2026/09/29
JO - IJID regions
DO - 10.1016/j.ijregi.2026.101025
UR - https://europepmc.org/article/MED/42921464
AB - Objectives The influenza A(H3N2) subclade K virus has predominated in the 2025-2026 season. This study compared the clinical severity of influenza between 2025-2026 and 2024-2025 seasons.Methods In this retrospective cohort study, a multicenter electronic health record database (TriNetX) was used. The clinical outcomes after influenza infection confirmed by nucleic acid detection were ecologically compared between the 2025-2026 and 2024-2025 seasons with propensity score matching.Results There were 8965 and 8937 children and 7488 and 6947 adults with confirmed influenza A(H3N2) infection in the 2025-2026 and 2024-2025 seasons, respectively. After each propensity score matching, the odds ratios for children and adults were not assessed (due to the small number of events) and 0.87 (95% confidence interval 0.71-1.05), P = 0.148 for death; 1.32 (1.10-1.59), P = 0.003 and 0.91 (0.82-1.02), P = 0.092 for critical care admission; 1.06 (0.97-1.16), P = 0.191 and 1.01 (0.94-1.08), P = 0.803 for hospitalization; 0.88 (0.73-1.07), P = 0.197 and 0.93 (0.83-1.04), P = 0.194 for mechanical ventilation; and 1.10 (0.91-1.32), P = 0.320 and 0.93 (0.83-1.03), P = 0.177 for vasopressor use, respectively.Conclusion In this electronic health record-based season-level comparison, no consistent adjusted differences were observed; however, the study could not directly assess subclade K-specific severity or rule out clinically relevant differences. Rapid and timely monitoring of clinical characteristics and severity in the case of an emerging influenza strain or subclade is important to guide preventive and therapeutic strategies against influenza.
SN - 2772-7076
ER -