TOP 51 - No Shot, All Shock: Pediatric Influenza Severity in the Era of Declining Vaccination

Publication Number: 2803.TOP 51

Victoria Danan, Cohen Children's Medical Center, LIC, NY, United States; Dzhamilya Abramova, Cohen Children's Medical Center, Brooklyn, NY, United States; Orli S. Strickman, Wheaton College, New York, NY, United States; Joanna Fishbein, Northwell Health, Plainview, NY, United States; Maria Teresa Santiago, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, New Hyde Park, NY, United States

Background: Influenza remains a major cause of global morbidity and mortality, yet vaccination uptake is declining, exacerbating disease severity. The 2024–2025 flu season saw some of the lowest pediatric vaccination rates, reaching only 49.2% of eligible children2, despite the vaccine's high effectiveness in preventing hospitalization. This low coverage coincided with an alarming rise in severe outcomes: the season recorded 280 pediatric influenza-associated deaths3, one of the highest tallies to date. Critically, nearly 90% of eligible children who died were not fully vaccinated3. The convergence of low protection and severe outcomes indicates that flu infections are now often presenting as a more severe phenotype, such as sepsis, in hospital settings. Sepsis, a dysregulated host in response to infection, presents unique diagnostic challenges in children due to the age-dependent variability in vital signs and immune function. Pediatric sepsis diagnosis relies on validated tools like the Phoenix Sepsis Score, which defines sepsis as dysfunction in two or more organ systems (e.g., breathing, circulation, or brain function) and identifies septic shock by severe cardiovascular compromise. While national mortality and hospitalization data are available, the specific presentation and septic phenotypic course of these hospitalized patients are not well-characterized.

Objective: To compare the severity and septic presentation of influenza in hospitalized pediatric patients during a low-vaccination season (2024–2025, 49.2% coverage) versus a high-vaccination season (2018–2019, 62.6% coverage), and to determine the association between individual patient vaccination status and critical outcomes, including clinical presentation, complication rates, and mortality.

Design/Methods: This retrospective cohort study compared pediatric patients hospitalized with laboratory-confirmed influenza across two seasons (low vaccination: 2024–2025; high vaccination: 2018–2019) at Cohen’s Children Medical Center. Data were extracted from Electronic Medical Records (EMR), including demographics, vaccination status, clinical presentation, treatments, and outcomes (e.g., Length of Stay, ICU admission, mechanical ventilation, and Phoenix Sepsis Score). Descriptive statistics will be presented. Multivariable regression analysis will be performed to assess the association between vaccination status and outcomes, adjusting for confounders such as age and underlying conditions.