{
  "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.",
  "abstract_shown": true,
  "affiliations": [
    "ICES"
  ],
  "article_type": "PUBLISHAHEADOFPRINT",
  "arxiv": null,
  "author_total": 24,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "J. C. Kwong"
    },
    {
      "name": "D. M. Goldfarb"
    },
    {
      "name": "M. Bhatt"
    },
    {
      "name": "J. Xie"
    },
    {
      "name": "S. A. Buchan"
    },
    {
      "name": "J. Papenburg"
    },
    {
      "name": "J. Cheng"
    },
    {
      "name": "M. Eltorki"
    },
    {
      "name": "Y. Finkelstein"
    },
    {
      "name": "V. Sabhaney"
    },
    {
      "name": "J. M. Pernica"
    },
    {
      "name": "J. Gravel"
    },
    {
      "name": "A. Kam"
    },
    {
      "name": "S. Berthelot"
    },
    {
      "name": "B. Burstein"
    },
    {
      "name": "J. Emsley"
    },
    {
      "name": "A. Mater"
    },
    {
      "name": "S. Ali"
    },
    {
      "name": "A. Shah"
    },
    {
      "name": "N. Poonai"
    },
    {
      "name": "D. Beer"
    },
    {
      "name": "P. Gill"
    },
    {
      "name": "J. Dickinson"
    },
    {
      "name": "S. Freedman"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/13m19axkpnknc.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.11.03.26367131",
  "fulltext_url": "https://www.medrxiv.org/content/10.64898/2026.11.03.26367131v1.full",
  "id": "13m19axkpnknc",
  "issns": [],
  "landing_url": "https://www.medrxiv.org/content/10.64898/2026.11.03.26367131v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "medrxiv",
      "pediatrics"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://www.medrxiv.org/content/10.64898/2026.11.03.26367131v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-03",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/13m19axkpnknc.ris",
  "sources": [
    {
      "first_seen": "2026-11-05T00:20:40Z",
      "native_id": "10.64898/2026.11.03.26367131",
      "source": "medrxiv",
      "url": "https://www.medrxiv.org/content/10.64898/2026.11.03.26367131v1"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "medrxiv:pediatrics",
      "subfield": "reproductive-child"
    }
  ],
  "title": "Pediatric Influenza Vaccine Effectiveness Against Emergency Visits and Hospitalization in Canada: 2024-2025 and 2025-2026 seasons",
  "title_text": "Pediatric Influenza Vaccine Effectiveness Against Emergency Visits and Hospitalization in Canada: 2024-2025 and 2025-2026 seasons",
  "type": "preprint",
  "updated_at": "2026-11-06T00:20:55Z",
  "url": "https://research.draconitic.com/paper/13m19axkpnknc",
  "venue": "medRxiv",
  "versions": []
}