Comparing two types of influenza vaccines for older adults in Galicia

Pragmatic Randomized Trial to Evaluate the Effectiveness of High-Dose Quadrivalent Influenza Vaccine vs. Standard-Dose Quadrivalent Influenza Vaccine in Adults Aged 65 to 79 Years in Galicia, Spain

PHASE4 · Hospital Clinico Universitario de Santiago · NCT06141655

This study is testing whether a high-dose flu vaccine works better than a standard-dose flu vaccine in preventing hospital visits for older adults aged 65 to 79 in Galicia during the upcoming flu seasons.

Quick facts

PhasePHASE4
Study typeInterventional
Enrollment114011 (estimated)
Ages65 Years to 79 Years
SexAll
SponsorHospital Clinico Universitario de Santiago (other)
Locations1 site (Santiago de Compostela, A Coruña)
Trial IDNCT06141655 on ClinicalTrials.gov

What this trial studies

This pragmatic randomized trial evaluates the effectiveness of high-dose quadrivalent influenza vaccine (QIV-HD) versus standard-dose quadrivalent influenza vaccine (QIV-SD) in reducing hospitalization risks for influenza or pneumonia among adults aged 65 to 79 in Galicia during the 2023/2024 and 2024/2025 seasons. Utilizing the Regional Vaccination Program of Galicia, the study will recruit and randomize at least 114,011 participants over two influenza seasons, collecting data through health registries for safety monitoring and follow-up. Participants will provide informed consent prior to vaccination and can withdraw from the study at any time.

Who should consider this trial

Good fit: Ideal candidates are community-dwelling adults aged 65 to 79 who are not eligible for the high-dose vaccine as part of standard care.

Not a fit: Patients who are not within the specified age range or who are eligible for the high-dose vaccine under standard care may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could lead to improved vaccination strategies that significantly reduce hospitalization rates for influenza in older adults.

How similar studies have performed: Previous studies have shown varying success with different influenza vaccine formulations, making this approach both relevant and potentially impactful.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* 1. Age 65-79 years residing in the community (only individuals who are not eligible to receive QIV-HD as part of the standard of care)
* 2. Informed consent form has been signed and dated

Exclusion Criteria:

* There are no specific exclusion criteria for this study

Where this trial is running

Santiago de Compostela, A Coruña

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.

View on ClinicalTrials.gov →

Conditions: Influenza

Last reviewed 2026-05-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.