High-Dose Quadrivalent Influenza Vaccine for Prevention of Cardiovascular and Respiratory Hospitalizations in Older Adults

Influenza Other Respir Viruses. 2024 Apr;18(4):e13270. doi: 10.1111/irv.13270.

Abstract

Background: We assessed the relative vaccine effectiveness (rVE) of high-dose quadrivalent influenza vaccine (QIV-HD) versus standard-dose quadrivalent influenza vaccine (QIV-SD) in preventing respiratory or cardiovascular hospitalizations in older adults.

Methods: FinFluHD was a phase 3b/4 modified double-blind, randomized pragmatic trial. Enrolment of 121,000 adults ≥65 years was planned over three influenza seasons (October to December 2019-2021). Participants received a single injection of QIV-HD or QIV-SD. The primary endpoint was first occurrence of an unscheduled acute respiratory or cardiovascular hospitalization (ICD-10 primary discharge J/I codes), from ≥14 days post-vaccination until May 31. The study was terminated after one season due to COVID-19; follow-up data for 2019-2020 are presented.

Results: 33,093 participants were vaccinated (QIV-HD, n = 16,549; QIV-SD, n = 16,544); 529 respiratory or cardiovascular hospitalizations (QIV-HD, n = 257; QIV-SD, n = 272) were recorded. The rVE of QIV-HD versus QIV-SD to prevent respiratory/cardiovascular hospitalizations was 5.5% (95% CI, -12.4 to 20.7). When prevention of respiratory and cardiovascular hospitalizations were considered separately, rVE estimates of QIV-HD versus QIV-SD were 5.4% (95% CI, -28.0 to 30.1) and 7.1% (95% CI, -15.0 to 25.0), respectively. Serious adverse reactions were <0.01% in both groups.

Conclusions: Despite insufficient statistical power due to the impact of COVID-19, rVE point estimates demonstrated a trend toward a benefit of QIV-HD over QIV-SD. QIV-HD was associated with lower respiratory or cardiovascular hospitalization rates than QIV-SD, with a comparable safety profile. Adequately powered studies conducted over multiple influenza seasons are needed to determine statistical significance of QIV-HD compared with QIV-SD against preventing respiratory and cardiovascular hospitalizations.

Trial registration: ClinicalTrials.gov number: NCT04137887.

Keywords: cardiovascular hospitalization; high‐dose quadrivalent influenza vaccine; pragmatic vaccine trial; respiratory hospitalization.

Publication types

  • Clinical Trial, Phase III
  • Clinical Trial, Phase IV
  • Pragmatic Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Aged
  • COVID-19* / prevention & control
  • Hospitalization
  • Humans
  • Influenza Vaccines*
  • Influenza, Human* / epidemiology
  • Influenza, Human* / prevention & control
  • Vaccines, Inactivated

Substances

  • Influenza Vaccines
  • Vaccines, Inactivated

Associated data

  • ClinicalTrials.gov/NCT04137887

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