Nationwide Utilization of Danish Government Electronic Letter System for Increasing InFLUenza Vaccine Uptake (NUDGE-FLU)

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. This study will investigate investigate whether digital behavioral nudges delivered via the official, mandatory Danish electronic letter system can increase influenza vaccine uptake among eligible influenza vaccination candidates.

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 identified as eligible for free-of-charge influenza vaccination in the Danish health system aged 18 years and above. Subjects will be identified through Danish nationwide health registries using codes from the International Classification of Diseases, 10th revision (ICD-10) and the Anatomical Therapeutic Chemical (ATC) classification system. Individuals will be randomized to 1 of 10 arms (1 control arm and 9 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. The study will be performed in collaboration with the Danish Health Data Authority and Statens Serum Institut.

• Study Type: Interventional
• Enrollment (Actual): 964870
• 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: 65 years and older (Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Age >=65 years at January 15, 2023 (eligible for free influenza vaccination in the official Danish vaccination program)
2. Access to the official, mandatory Danish electronic mailbox system

Exclusion Criteria:

1) Persons living in nursing homes

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

10

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
No Intervention: Control; No letter
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.
Experimental: Priming & Hot State Activation - 1 reminder; 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: Depersonalized Letter; The standard letter without the recipient's name	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: Gain-Framing/Context; Text added to the standard letter employing the specified behavioral economic principle	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/Context; Text added to the standard letter employing the specified behavioral economic principle	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: Collective Goal; Text added to the standard letter employing the specified behavioral economic principle	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: Active Choice/Implementation Intention Prompt; Text added to the standard letter employing the specified behavioral economic principle	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 Frame; Text added to the standard letter employing the specified behavioral economic principle	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: Expert Authority; Text added to the standard letter employing the specified behavioral economic principle	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 a hospitalization with influenza or pneumonia	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 with a hospitalization due to COVID-19	Up to 8 months
Number of participants who received a COVID-19 vaccine	Up to 3 months

Collaborators and Investigators

• Sponsor: Tor Biering-Sørensen
• Collaborators: Sanofi Pasteur, a Sanofi Company; Statens Serum Institut
• Investigators: Principal Investigator: Tor Biering-Sørensen, MD, PhD, MPH, Research Director

Study record dates

Study Major Dates

• Study Start (Actual): September 16, 2022
• Primary Completion (Actual): January 1, 2023
• Study Completion (Actual): May 31, 2023

Study Registration Dates

• First Submitted: August 31, 2021
• First Submitted That Met QC Criteria: September 13, 2022
• First Posted (Actual): September 15, 2022

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: FLU00180

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