Nationwide Utilization of Danish Government Electronic Letter System for Confirming the Effectiveness of Behavioral Nudges in Increasing InFLUenza Vaccine Uptake Among Older Adults (NUDGE-FLU-2)

In randomized clinical trials and observational studies, influenza vaccination has been shown to be effective in reducing influenza-related illness, hospitalizations, cardiovascular events, and mortality in select populations. However, the real-world effectiveness of influenza vaccination is limited by its uptake. Conducted during the 2022/2023 influenza season, the first NUDGE-FLU trial demonstrated the effectiveness of two electronic behavioral nudging letter strategies in increasing influenza vaccination rates among older adults in Denmark - a letter highlighting potential cardiovascular benefits of vaccination and a standard informational letter sent at baseline and repeated at day 14. This present study will once again investigate whether digital behavioral nudges delivered via the official, mandatory Danish electronic letter system can increase influenza vaccine uptake among older adults including whether the effectiveness of previously successful strategies can be confirmed during a subsequent influenza season.

Study Overview

• Status: Completed
• Conditions: Influenza; Behavior and Behavior Mechanisms
• Intervention / Treatment: Behavioral: Behavioral Economic Principles

Detailed Description

The study is a prospective, randomized, open-label implementation trial. The study population will consist of persons aged >=65 years at January 15, 2024 - this age group is eligible for free-of-charge influenza vaccination in the official Danish vaccination program. Subjects will be identified through Danish nationwide health registries including the Danish Civil Registration System. Individuals will be randomized to 1 of 7 arms (1 usual care arm and 6 intervention arms) with each testing different nudging strategies employing various behavioural economic principles. The interventions will be delivered through the official, mandatory Danish electronic letter system. All subject data will be retrieved from the Danish nationwide registries with the exception of information on intervention allocation. Endpoints will be retrieved at prespecified dates using prespecified search algorithms.

• Study Type: Interventional
• Enrollment (Actual): 881373
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Denmark
  • Hovedstaden
    • Hellerup, Hovedstaden, Denmark, 2900
      • Center for Translational Cardiology and Pragmatic Randomized Trials, Department of Cardiology, Copenhagen University Hospital - Herlev and Gentofte

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Age >=65 years at January 15, 2024 (eligible for free-of-charge influenza vaccination in the Danish public health system)
2. Access to the official, mandatory Danish electronic mailbox system

Exclusion Criteria:

1. Persons living in nursing homes (approximated as any person living at an address with >=6 inhabitants aged 80 years and above)
2. Known to have already scheduled influenza vaccination appointment

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

7

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Standard Letter; This group will receive a standard letter on the benefits of influenza vaccination without behavioral economic enhancement	Behavioral: Behavioral Economic Principles; The control arm will receive no letter to reflect the background vaccination uptake. Intervention arms will test the effects of different letters developed using behavioral economic principles.
No Intervention: Usual Care; No letter
Experimental: Repeated Letter; The standard letter sent out two times instead of once	Behavioral: Behavioral Economic Principles; The control arm will receive no letter to reflect the background vaccination uptake. Intervention arms will test the effects of different letters developed using behavioral economic principles.
Experimental: Cardiovascular Gain-Framing Letter; Text added to the standard letter highlighting potential cardiovascular benefits of influenza vaccination	Behavioral: Behavioral Economic Principles; The control arm will receive no letter to reflect the background vaccination uptake. Intervention arms will test the effects of different letters developed using behavioral economic principles.
Experimental: Respiratory Gain-Framing Letter; Text added to the standard letter highlighting potential respiratory disease-related benefits of influenza vaccination	Behavioral: Behavioral Economic Principles; The control arm will receive no letter to reflect the background vaccination uptake. Intervention arms will test the effects of different letters developed using behavioral economic principles.
Experimental: Implementation Intention Prompt Letter; Implementation intention prompt added to the standard letter	Behavioral: Behavioral Economic Principles; The control arm will receive no letter to reflect the background vaccination uptake. Intervention arms will test the effects of different letters developed using behavioral economic principles.
Experimental: Loss-Framing Letter; Text added to the standard letter highlighting potential risks of not receiving influenza vaccination	Behavioral: Behavioral Economic Principles; The control arm will receive no letter to reflect the background vaccination uptake. Intervention arms will test the effects of different letters developed using behavioral economic principles.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Number of participants who received an influenza vaccine	Up to 3 months

Secondary Outcome Measures

Outcome Measure	Time Frame
Time from intervention delivery to influenza vaccination	Up to 3 months

Other Outcome Measures

Outcome Measure	Time Frame
Number of participants with laboratory-confirmed influenza	Up to 8 months
Number of participants with any hospitalization	Up to 8 months
All-cause mortality	Up to 8 months
Composite of incident heart failure, heart failure hospitalization, or cardiovascular death	Up to 8 months
Composite of myocardial infarction, stroke, or cardiovascular death	Up to 8 months
Composite of myocardial infarction, coronary revascularization, stroke, or cardiovascular death	Up to 8 months
Number of participants with incident heart failure or heart failure hospitalization	Up to 8 months
Cardiovascular death	Up to 8 months
Number of participants with myocardial infarction	Up to 8 months
Number of participants with coronary revascularization	Up to 8 months
Number of participants with stroke	Up to 8 months
Number of contacts to general practitioner (excluding vaccination visit)	Up to 8 months
Number of participants with laboratory-confirmed COVID-19	Up to 8 months
Number of participants who received a COVID-19 vaccine	Up to 3 months
Number of participants with a hospitalization for influenza or pneumonia	Up to 8 months
Number of participants with a hospitalization for any respiratory disease	Up to 8 months
Number of participants with a hospitalization for any cardio-respiratory disease	Up to 8 months
Number of participants with a hospitalization for any cardiovascular disease	Up to 8 months
Total number of hospitalizations (first and recurrent)	Up to 8 months
Total number of heart failure events (incident heart failure and first and recurrent heart failure hospitalizations)	Up to 8 months
Number of participants with incident atrial fibrillation or atrial fibrillation hospitalization	Up to 8 months
Number of participants with a hospitalization for COVID-19	Up to 8 months
Number of participants who filled a prescription for any guideline-directed medical therapy for heart failure	Up to 8 months
Total number of filled prescriptions for guideline-directed medical therapy for heart failure	Up to 8 months
Number of participants who filled a prescription for a sodium-glucose cotransporter 2 inhibitor or glucagon-like peptide 1 receptor agonist	Up to 8 months

Collaborators and Investigators

• Sponsor: Tor Biering-Sørensen
• Collaborators: Statens Serum Institut
• Investigators: Principal Investigator: Tor Biering-Sørensen, MD, MSc, MPH, PhD, Center for Translational Cardiology and Pragmatic Randomized Trials, Department of Cardiology, Copenhagen University Hospital - Herlev and Gentofte

Study record dates

Study Major Dates

• Study Start (Actual): September 14, 2023
• Primary Completion (Actual): January 1, 2024
• Study Completion (Actual): May 31, 2024

Study Registration Dates

• First Submitted: August 31, 2023
• First Submitted That Met QC Criteria: September 8, 2023
• First Posted (Actual): September 11, 2023

Study Record Updates

• Last Update Posted (Actual): October 10, 2024
• Last Update Submitted That Met QC Criteria: October 8, 2024
• Last Verified: October 1, 2024

More Information

Terms related to this study

• Keywords: Influenza; Vaccination; Behavioral Science; Nudging
• Additional Relevant MeSH Terms: RNA Virus Infections; Virus Diseases; Infections; Respiratory Tract Infections; Respiratory Tract Diseases; Orthomyxoviridae Infections; Influenza, Human
• Other Study ID Numbers: NUDGE-FLU-2

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Data will be collected from Danish administrative health registries, which are subject to Danish legislation and can only be made available to a third party under certain conditions. Please contact the sponsor-investigator in case of any inquiries.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No