Influenza Disease and Vaccination
Influenza activity has been increasing for the past few weeks. Centers for Disease Control and Prevention (CDC) influenza surveillance week 50 shows increasing influenza with children especially impacted. Influenza-like illness last week, was highest in those 0-4 years (11.2%) followed by 5–24-year-olds (7.5%).1 Emergency department visits for influenza were also significant youth accounting for 9.2% of 5-17 year-old visits and 7% of visits for those 0-4 years-old.1
Among typed influenza viruses, about 90% are influenza A (H3N2), predominantly the drifted clade 2a.3a.1 subclade K.1 As you have likely heard, the subclade K is a drifted variant and thus not optimally matched to the H3N2 strain included in the 2025-2026 influenza vaccine.1 Despite the mismatch, vaccine effectiveness against severe disease and outcomes in pediatrics appears strong. Preliminary data from the United Kingdom suggest that the vaccine has 74.7% (95% CI 52.3 – 87.9) effectiveness against emergency department visits and 72.8% (95% CI 48.3-87.1) effectiveness against hospital admission in children 2-17 years, respectively.2 These findings reinforce the role of influenza vaccination in preventing severe disease in children.
Unfortunately, pediatric influenza vaccination rates are concerningly low with only 40.8% of US children currently vaccinated against influenza.3 Pharmacists play a critical role in educating parents, addressing vaccine hesitance, and reinforcing that vaccination remains important throughout the influenza season.
Key influenza vaccine points to remember4-6:
- The only way to protect children < 6 months of age is via maternal immunization at least 2 weeks prior to delivery.
- Children 6 months to ≤ 9 years who have not previously received 2 doses of influenza vaccine, require 2 doses this season, separated by ≥ 28 days.
- Other patients should receive 1 dose of influenza vaccine this year.
- Protective immunity takes about 2 weeks (for those needing 2 doses, the 2-week count begins after the second dose).
Influenza Treatment Recommendations
If children become sick with influenza, it is important to ensure they receive guideline recommended treatments. Data from 2023-2024 US influenza season indicate substantial underutilization of anti-influenza therapy in pediatric patients. Only 31% pediatric outpatients and 52-59% hospitalized pediatric patients with influenza received recommended treatment.7 Clinician surveys using pediatric case scenarios highlight gaps in guideline adherence. In March – June 2024, two surveys (1 outpatient and 1 inpatient) with clinical pediatric influenza cases was sent to prescribers in 7 children’s hospitals and their affiliated community hospitals.8,9 In the outpatient analysis, clinicians generally only recommended treatment for one of the three recommended cases.9 Approximately 50% of inpatient providers recommended therapy for the hospitalized pediatric influenza cases (32% – 59%, depending on the case).8 In both studies, pediatric infectious diseases physicians were most likely to choose oseltamivir treatment, with the generalists (e.g., pediatric primary care or hospitalists) least likely.8,9
Importantly, the CDC reports that anti-influenza treatments (e.g., neuraminidase inhibitors, PA Cap-Dependent Endonuclease Inhibitor) continue to be effective against the circulating strains, including H3N2 subclade K.1 The Infectious Diseases Society of America, American Academy of Pediatrics, and Centers for Disease Control and Prevention all recommend prompt treatment with oseltamivir, regardless of duration of symptoms for all patients with high risk conditions.
Pediatric Patients that are at high risk and should receive treatment with oseltamivir, regardless of duration of symptoms: 10-12
- All < 2 years of age per CDC 11 or < 5 years of age AAP 12;
- All with underlying conditions that increase risk for complications,
- All with severe, complicated, or progressing disease,
- All who are hospitalized with influenza disease.
Consider those with uncomplicated disease who present within 48 hours of symptoms may receive antiviral treatment with any of the neuraminidase inhibitors (i.e., oseltamivir, zanamivir, peramivir) or baloxavir, that are age appropriate (see Table 1).11,12
Pediatric Specific Outcome Data
Outcome data for anti-influenza treatment in pediatric patients are limited. Available evidence suggests benefits in prompt treatment of pediatric patients in the outpatient and hospital settings. Walsh and colleagues evaluated the impact of prompt anti-influenza treatment in pediatric patients hospitalized with influenza.13 They included almost 56,000 pediatric patients from multiple centers from 2007 – 2020 in a retrospective analysis. Those who received prompt oseltamivir within day 0-1 of hospitalization had reduced length of stay, decreased 7-day hospital readmission, and lower risk of ECMO use/death compared to those who received delayed or no oseltamivir treatment.13 In the outpatient setting, an individual patient meta-analysis was performed including 5 trials and 2,561 pediatric patients who were randomized to receive oseltamivir or placebo within 48 hours of symptom onset.14 Oseltamivir reduced symptom duration by 17.6 hours (0.7 – 34.5 hours) and had a 34% risk reduction in acute otitis media infections. An increase in vomiting was found in those that received oseltamivir (RR 1.63 (95% CI 1.3-2.04).14
Pharmacists Role
With the increasing influenza disease activity, pharmacists have an essential role to ensure parents understand the importance and effectiveness of the influenza vaccination. In addition, cases of clinical influenza disease provides an antimicrobial stewardship opportunity to recommend appropriate anti-influenza therapy in high-risk pediatric patients.
Table 1. Anti-Influenza Medications for Treatment of Influenza Disease11,15
| Medication | FDA approval ages for treatment | Notes |
| Oseltamivir (Tamiflu®) | ≥ 14 days-old (any age) | Intermittent shortage reported for some manufacturers as of Dec 2025 |
| Zanamivir (Relenza®) | ≥ 7 years-old | Do not use in those with respiratory disease or lactose/milk protein allergy |
| Peramivir (Rapivab™) | ≥ 6 months-old | |
| Baloxavir (Xofluza®) | ≥ 5 years | Do not crush tablets, instead use suspension packets in those < 20 kg or who cannot take tablets. Not recommended as monotherapy for immunocompromised |
References
- Centers for Disease Control and Prevention. FluView:Weekly US Influenza Surveillance Report. Accessed December 23, 2025https://www.cdc.gov/fluview/surveillance
- Kirsebom FC, Thompson C, Talts T, et al. Early influenza virus characterisation and vaccine effectiveness in England in autumn 2025, a period dominated by influenza A(H3N2) subclade K. Euro Surveill. 2025;30(46):2500854. doi: 10.2807/1560
- Centers for Disease Control and Prevention. FluVaxView. Accessed Deccember 23, 2025. Available at: https://www.cdc.gov/fluvaxview/dashboard/vaccine-doses-distributed.html
- American Academy of Pediatrics, Committee on Infectious Diseases. Red Book : Report of the Committee on Infectious Diseases 2024 – 2027. AAP Immunization Schedule. Accessed December 12, 2025. Available at: https://publications.aap.org/redbook/resources/15585/AAP-Immunization-Schedule
- American Academy of Family Physicians. Immunization Schedules. Accessed December 12, 2025. Available at: https://www.aafp.org/family-physician/patient-care/prevention-wellness/immunizations-vaccines/immunization-schedules.html
- Centers for Disease Control and Prevention. Child and Adolescent Immunization Schedule by Age (Addendum updated August 7, 2025). Accessed September 20, 2025. Available at: https://www.cdc.gov/vaccines/hcp/imz-schedules/child-adolescent-age.html
- Frutos AM, Ahmad HM, Ujamaa D, et al. Underutilization of Influenza Antiviral Treatment Among Children and Adolescents at Higher Risk for Influenza-Associated Complications – United States, 2023-2024. MMWR Morb Mortal Wkly Rep. 2024;73(45):1022–1029
- Bassett HK, Rao S, Beck J, et al. Variability of Clinician Recommendations for Oseltamivir in Children Hospitalized with Influenza. Pediatrics. 2025;155(5):e2024069111. doi: 10.1542/peds.2024–069111
- Bassett HK, Rao S, Beck J, et al. Clinician Preferences for Oseltamivir Use in Children With Influenza in the Outpatient Setting. Pediatrics. 2025;156(3):e2025071193. doi: 10.1542/peds.2025–071193
- Uyeki TM, Bernstein HH, Bradley JS, et al. Clinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenza. Clin Infect Dis. 2019;68(6):895–902
- Centers for Disease Control and Prevention. Influenza Antiviral Medications: Summary for Clinicians. Accessed December 23, 2025. Available at: https://www.cdc.gov/flu/hcp/antivirals/summary-clinicians.html
- Committee on Infectious Diseases. Recommendations for Prevention and Control of Influenza in Children, 2025-2026: Policy Statement. Pediatrics. 2025;156(6):e2025073620. doi: 10.1542/peds.2025–073620
- Walsh PS, Schnadower D, Zhang Y, et al. Association of Early Oseltamivir with Improved Outcomes in Hospitalized Children with Influenza, 2007-2020. JAMA Pediatr. 2022;176(11):e223261
- Malosh RE, Martin ET, Heikkinen T, et al. Efficacy and Safety of Oseltamivir in Children: Systematic Review and Individual Patient Data Meta-analysis of Randomized Controlled Trials. Clin Infect Dis. 2018;66(10):1492–1500
- Michelle Wheeler. ASHP Drug Shortages – Current Shortages. Accessed December 23, 2025. Available at: https://www.ashp.org/drug-shortages/current-shortages/drug-shortage-detail.aspx?id=881&loginreturnUrl=SSOCheckOnly