Influenza Vaccine Dose and Dementia Outcomes - Summary - MDSpire

Influenza Vaccine Dose and Dementia Outcomes

  • By

  • Kathryn Wighton

  • April 10, 2026

  • 3 min

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Objective:

To investigate the association between high-dose influenza vaccination and the risk of incident Alzheimer dementia in patients aged 65 and older.

Key Findings:
  • High-dose vaccination associated with lower cumulative risk of Alzheimer dementia from months 1 to 25.
  • Maximum absolute risk difference was approximately 0.5%, with a number needed to treat of 185 at month 25.
  • Risk ratios ranged from about 0.78 to 0.89, indicating consistently lower risk with high-dose vaccination.
  • Stronger association observed among women compared to men.
  • Sustained seasonal high-dose vaccination also linked to lower Alzheimer dementia risk.
Interpretation:

High-dose influenza vaccination may reduce the risk of incident Alzheimer dementia in older adults, but causality cannot be established.

Limitations:
  • Follow-up limited to 3 years.
  • Mortality data not available.
  • Lack of sociodemographic or lifestyle variables in the database.
  • Potential misclassification in claims-based data.
  • Residual confounding, including healthy-vaccinee bias, may have influenced findings.
Conclusion:

High-dose influenza vaccine is associated with a significantly lower risk of incident Alzheimer dementia for the first 25 months post-vaccination, with a minimum number needed to treat of 185.

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