Clinical Scorecard: Comparative Effectiveness of Adjuvanted and High-Dose Influenza Vaccines Against Confirmed Influenza Outcomes, Including Hospitalizations, in Older Adults During the 2022–2023 and 2023–2024 Seasons

At a Glance

Key Highlights

• Adults aged ≥65 years account for an estimated 70% to 85% of seasonal influenza-related deaths and 50% to 70% of influenza-related hospitalizations in recent years.

• The ACIP has preferentially recommended adjuvanted or higher-dose influenza vaccines over standard-dose unadjuvanted vaccines for adults aged ≥65 years since 2022.

• In the 2023–2024 season, aQIV and HD-QIV had comparable effectiveness against test-confirmed influenza in any setting and in ED/hospitalization settings.

• Pooled 2022–2024 analyses also showed comparable effectiveness between aQIV and HD-QIV against test-confirmed influenza hospitalizations in both the overall and high-risk older adult populations.

Guideline-Based Recommendations

Diagnosis

• This study does not establish a diagnostic guideline. For study eligibility, influenza testing occurred within ±7 days of an acute respiratory or febrile illness diagnosis.

Management

• The source notes that annual influenza vaccination is recommended for adults at high risk of complications, including those aged ≥65 years, and that ACIP preferentially recommends adjuvanted or higher-dose vaccines over standard-dose unadjuvanted vaccines for this age group.

Monitoring & Follow-up

• The study evaluated test-confirmed influenza across multiple care settings and test-confirmed influenza hospitalizations in overall and high-risk older adults. It did not establish a specific clinical monitoring protocol.

Risks

• Adults aged ≥65 years are at increased risk of severe influenza, reflecting both the high prevalence of chronic comorbidities and age-related decline in immune function.

Patient & Prescribing Data

The 2023–2024 analysis included 37,377 vaccinated and tested adults aged ≥65 years, including 14,866 aQIV recipients and 22,511 HD-QIV recipients. The study compared relative vaccine effectiveness rather than evaluating a specific prescribing regimen.

Clinical Best Practices

• Follow current recommendations favoring adjuvanted or higher-dose influenza vaccines over standard-dose unadjuvanted vaccines for adults aged ≥65 years.

• Recognize that aQIV and HD-QIV showed comparable effectiveness against test-confirmed influenza outcomes in this study.

• Consider high-risk medical conditions when assessing older adults because these conditions are associated with greater vulnerability to severe influenza outcomes.

Related Resources & Content

1. Centers for Disease Control and Prevention. Flu and people 65 years and older. 2024.

2. World Health Organization. Global influenza strategy. 2019.

3. Grohskopf LA, Blanton LH, Ferdinands JM, Chung JR, Broder KR, Talbot HK, et al. Prevention and control of seasonal influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices—United States, 2022-23 influenza season. MMWR Recomm Rep. 2022;71:1-28.

4. Grohskopf LA, Ferdinands JM, Blanton LH, Broder KR, Loehr J. Prevention and control of seasonal influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices—United States, 2024-25 influenza season. MMWR Recomm Rep. 2024;73:1-25.

5. Domnich A, de Waure C. Comparative effectiveness of adjuvanted versus high-dose seasonal influenza vaccines for older adults: a systematic review and meta-analysis. Int J Infect Dis. 2022;122:855-863.

6. Imran M, Chastek B, Bancroft T, Webb N, Pelton SI, Haag MDM, et al. Comparable effectiveness of MF59-adjuvanted and high-dose quadrivalent inactivated influenza vaccines for prevention of test-confirmed influenza during the 2022-2023 influenza season. Int J Infect Dis. 2025;159:107983.