Who Gets High-Dose Flu Vaccine
All adults aged 65 years and older should receive a high-dose or enhanced influenza vaccine (HD-IIV3, aIIV3, or RIV3) preferentially over standard-dose vaccines. 1
Primary Indication: Age ≥65 Years
The ACIP makes a clear preferential recommendation for adults aged ≥65 years to receive one of three enhanced vaccine formulations 1:
- High-dose inactivated influenza vaccine (HD-IIV3)
- Adjuvanted inactivated influenza vaccine (aIIV3)
- Recombinant influenza vaccine (RIV3)
If none of these three enhanced vaccines is available at the time of vaccination, any other age-appropriate influenza vaccine should be used rather than delaying vaccination 1. The evidence base is strongest for HD-IIV3, followed by aIIV3, then RIV3 2.
Special Population: Solid Organ Transplant Recipients
Solid organ transplant recipients aged 18-64 years who are receiving immunosuppressive medication regimens may receive either HD-IIV3 or aIIV3 as acceptable options, though ACIP does not express a preference over other age-appropriate vaccines for this group 1. This represents the only FDA-approved off-label indication for high-dose vaccine in adults under 65 years.
Evidence Supporting Enhanced Vaccines in Older Adults
Recent meta-analyses demonstrate that HD-IIV provides superior protection compared to standard-dose vaccines 3:
- 38.5% relative vaccine effectiveness against hospitalization for influenza
- 31.2% relative effectiveness against laboratory-confirmed influenza
- 11.5% relative effectiveness against pneumonia or influenza hospitalization
- 7.5% relative effectiveness against cardiorespiratory hospitalization
- 3.3% relative effectiveness against all-cause hospitalization
Cardiovascular Benefits
The cardiovascular protective effects are particularly notable. HD-IIV reduces 4:
- Hospitalization for any cardiovascular disease by 6.6%
- Hospitalization for heart failure by 21.3%
- Hospitalization for respiratory disease by 6.5%
These benefits occur regardless of whether patients have pre-existing cardiovascular disease 4, making the age-based recommendation straightforward without requiring additional risk stratification.
Long-Term Care Residents
Long-term care facility residents aged ≥65 years should receive enhanced vaccines based on the same age-based recommendation 1. Both HD-IIV3 and aIIV3 demonstrate comparable immunogenicity in this population 5, supporting either choice when available.
What About Younger High-Risk Adults?
High-dose vaccine is NOT indicated for adults under 65 years based on chronic conditions alone (heart disease, lung disease, kidney disease, diabetes, or immunocompromised status), with the single exception of solid organ transplant recipients on immunosuppression 1. These younger high-risk individuals should receive standard age-appropriate influenza vaccines.
Common Pitfall to Avoid
Off-label use of HD-IIV in adults aged 50-64 years has occurred in practice 6, but this is not supported by FDA approval or ACIP recommendations. The enhanced vaccines are not approved for use below age 65 (except the specific transplant population noted above) 7.
Practical Implementation Algorithm
Is the patient ≥65 years old?
- Yes → Offer HD-IIV3, aIIV3, or RIV3 preferentially
- No → Proceed to step 2
Is the patient aged 18-64 AND a solid organ transplant recipient on immunosuppression?
- Yes → May offer HD-IIV3 or aIIV3 (without preference over standard vaccines)
- No → Use age-appropriate standard-dose vaccine
If enhanced vaccine unavailable for patient ≥65 years:
- Give any available age-appropriate vaccine rather than delaying 1
The recommendation is straightforward and age-based, requiring no complex risk stratification beyond confirming age ≥65 years 1, 2.