Study to Evaluate the Effectiveness of a High-Dose Quadrivalent Influenza Vaccine (QIV-HD) Compared to a Standard-Dose Quadrivalent Influenza Vaccine (QIV-SD) in Adults 65 Years of Age and Older

Relative Effectiveness of a High-Dose Quadrivalent Influenza Vaccine Versus a Standard-Dose Quadrivalent Influenza Vaccine in Subjects 65 Years of Age and Older

Primary Objective:

To demonstrate the superior relative effectiveness of QIV-HD as compared to QIV-SD among persons 65 years of age and older for the prevention of cardiovascular and/or respiratory hospitalizations.

Secondary Objective:

• To assess the clinical relative effectiveness of QIV-HD as compared to QIV-SD in prevention of:
• inpatient hospitalization for selected circulatory and respiratory causes
• death, either all-cause or cardiovascular or respiratory causes
• inpatient hospitalization (using primary and secondary discharge diagnoses)
• inpatient hospitalization (using admission diagnoses)
• hospital emergency room visits
• primary care visits to physician or
• major acute cardiovascular events (MACE)
• To assess the characteristics of inpatient hospitalization or hospital emergency room visits or primary care visits to physician by QIV-HD and QIV-SD groups.
• To describe the clinical relative effectiveness of QIV-HD as compared to QIV-SD:
• by age group and by group with specific comorbidities
• for different periods of observation
• To describe all serious adverse events (SAEs) (including adverse event of special interest [AESIs]) for all subjects in both QIV-HD and QIV-SD groups.

Study duration per participant was 1 day of screening and vaccination. The study was planned to be conducted over a period of 3 influenza seasons beginning in 2019-2020. The vaccination period was from October to December.

Inclusion criteria:

- Aged 65 years or older on the day of inclusion ("65 years" means from the day of the 65th birthday).

Exclusion criteria:

• Participation at the time of study enrollment (or in the 4 weeks [28 days] preceding the study vaccination) or planned participation during the present study period in another clinical study investigating a vaccine, drug, medical device, or medical procedure.
• Previous vaccination against influenza (in the preceding 6 months) with either the study vaccines or another vaccine.
• Known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to the vaccines used in the study or to a vaccine containing any of the same substances.

The above information was not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.