What is the expected effectiveness of the flu shot for the 2025-2026 influenza season, especially for high-risk individuals such as the elderly, young children, and people with chronic health conditions?

Flu Shot Effectiveness 2025-2026

The influenza vaccine for the 2025-2026 season is expected to provide moderate to good protection, with effectiveness ranging from 34-65% depending on age group and circulating strain match, and most importantly reduces mortality by 65% in children and 45-68% in elderly adults—making annual vaccination essential for all persons aged ≥6 months, particularly high-risk groups. 1, 2

Expected Effectiveness by Population

Children and Young Adults (6 months to 64 years)

• Vaccine effectiveness in children aged 6 months to 8 years ranges from 34-59% depending on the circulating strain match 1
• The vaccine reduces influenza-associated death in children by 65% overall and 51% in children with underlying conditions 1
• Historically, up to 80% of influenza-associated pediatric deaths occur in unvaccinated or incompletely vaccinated children 1
• Vaccination prevented an estimated 116 deaths in children aged 6 months through 17 years during the 2022-2023 season 1
• Vaccination reduces life-threatening influenza illness by 75% in children 1

Elderly Adults (≥65 years)

• High-dose or adjuvanted vaccines demonstrate superior protection in adults ≥65 years, with 24.2% relative efficacy improvement over standard-dose vaccines 3
• The vaccine reduces mortality by 45-68% and hospitalizations by 50% in elderly adults 4
• Among nursing home residents aged >65 years, high-dose vaccine reduced respiratory-related hospital admissions (3.4% vs. 3.9%) and mortality (17.1% vs. 18.3%) compared to standard-dose vaccine 3
• Effectiveness is most pronounced in adults aged ≥75 years, though benefits extend to all individuals ≥65 years regardless of comorbidities, frailty, or prior vaccination history 3

High-Risk Populations

• Children younger than 5 years (especially under 2 years) and those with underlying conditions face the highest risk of complications 1
• Black, Hispanic, and American Indian/Alaska Native children have 3-4 fold higher influenza-associated in-hospital deaths 1
• Patients with chronic pulmonary disease, cardiovascular disease, and immunosuppression should be prioritized for vaccination 1

2025-2026 Vaccine Composition

All influenza vaccines available in the United States during the 2025-26 season will be trivalent vaccines containing: 2

• Influenza A/Victoria/4897/2022 (H1N1)pdm09-like virus (egg-based) or A/Wisconsin/67/2022 (H1N1)pdm09-like virus (cell-based/recombinant)
• Influenza A/Thailand/8/2022 (H3N2)-like virus (egg-based) or A/Massachusetts/18/2022 (H3N2)-like virus (cell-based/recombinant)
• Influenza B/Austria/1359417/2021 (Victoria lineage)-like virus

The influenza A (H3N2) vaccine component for the 2024-2025 season was updated from the previous year, while the influenza A (H1N1) and influenza B Victoria lineage remain unchanged 5

Vaccine Selection Algorithm

For Adults 18-64 Years (Not Pregnant or Immunocompromised)

Administer standard-dose trivalent or quadrivalent (cell-based, egg-based, MF59-adjuvanted, or recombinant) influenza vaccine 6

For Adults ≥65 Years (Not Immunocompromised)

Administer high-dose trivalent or high-dose quadrivalent egg-based influenza vaccine preferentially 6, 3

• High-dose vaccine (Fluzone High-Dose) contains 60 μg of hemagglutinin per strain (four times the standard dose) 3
• If high-dose vaccine is not available, administer standard-dose vaccine rather than delaying vaccination 3

For Children 6 Months Through 8 Years

Dosing depends on vaccination history: 5

• Children receiving influenza vaccine for the first time OR who received only 1 dose before July 1,2024, OR whose vaccination status is unknown: 2 doses at least 4 weeks apart
• All other children: 1 dose
• Any licensed influenza vaccine product appropriate for age and health status is acceptable (IIV, LAIV, or RIV for ≥18 years) 5

For Immunocompromised Patients

• Use only inactivated (IIV) or recombinant (RIV) vaccines—never live attenuated (LAIV/nasal spray) 1
• Solid organ transplant recipients aged 18-64 years on immunosuppressive medications may receive high-dose or adjuvanted vaccines 3
• For patients who received anti-B cell therapies, defer vaccination for 6 months after the last dose, ideally once B cell recovery is evident 3

For Patients with Chronic Pulmonary Conditions

Use only inactivated or recombinant vaccines—never live attenuated (nasal spray) 1

Additional Benefits Beyond Influenza Prevention

• Antibiotic prescription rates in ambulatory children decline by 3 per 1000 person-months for each 1% increase in vaccination coverage 1
• Vaccination reduces influenza-associated otitis media in young children by approximately 30% 1
• Decreased work absenteeism and healthcare resource utilization occur when vaccine and circulating strains are well-matched 1

Critical Implementation Points

Timing: Vaccination should ideally be received by the end of October for optimal protection before influenza season peaks 5

• Most adults, particularly those ≥65 years, should not be immunized in July and August due to concerns about waning immunity 3
• Children recommended to receive 2 doses should start vaccination as soon as vaccine becomes available 5

Product Selection: Vaccination should not be delayed to obtain a specific product—when multiple appropriate products exist, any licensed vaccine is acceptable 1, 5

Annual Requirement: Annual vaccination is required due to antigenic drift and waning immunity—prior vaccination does not provide multi-year protection 1

New for 2025-2026: Children aged ≤18 years, pregnant women, and all adults should receive seasonal influenza vaccines only in single-dose formulations that are free of thimerosal as a preservative 2

Common Pitfalls to Avoid

• Do not delay vaccination in high-risk patients waiting for "optimal timing"—the risk of missing vaccination entirely outweighs timing concerns 1
• Do not assume prior vaccination provides multi-year protection—annual vaccination is mandatory 1
• Do not overlook racial and ethnic disparities—minority populations have significantly higher mortality rates 1
• Do not confuse high-dose formulations with standard-dose—high-dose vaccine is available as a prefilled syringe and should not be confused with standard-dose formulations 3
• Do not use live attenuated vaccine (LAIV) in immunocompromised persons or those with chronic medical conditions 5, 1

Safety Profile

• Local soreness at the injection site is the most frequent side effect, typically lasting up to 2 days and generally mild 4
• Systemic symptoms including fever, malaise, and myalgias may begin 6-12 hours after vaccination and typically last 1-2 days, occurring no more frequently than with placebo 4
• The vaccine does not contain live virus and cannot cause clinical influenza infection 4
• High-dose vaccine recipients may experience more frequent injection site reactions and systemic symptoms compared to standard-dose recipients, though the safety profile remains favorable 3
• Guillain-Barré syndrome was clearly associated only with the 1976 swine influenza vaccine and has not been associated with influenza vaccines since 1976 4