Nationwide Utilization of Danish Government Electronic Letter System for Confirming the Effectiveness of Behavioral Nudges in Increasing InFLUenza Vaccine Uptake Among Older Adults

Not Applicable

Completed

• Conditions: Behavior and Behavior Mechanisms; Influenza
• Interventions: Behavioral: Behavioral Economic Principles

• Registration Number: NCT06030726
• Lead Sponsor: Tor Biering-Sørensen

Brief Summary

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.

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 Timeline

• Study First Submitted: 2023-08-31
• Study First Submitted QC: 2023-09-08
• Study First Posted: 2023-09-11
• Study Start: 2023-09-14
• Primary Completion: 2024-01-01
• Study Completion: 2024-05-31
• Status Verified: 2024-10
• Last Update Submitted: 2024-10-08
• Last Update Posted: 2024-10-10

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 881373

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 & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Cardiovascular Gain-Framing Letter	Behavioral Economic Principles	Text added to the standard letter highlighting potential cardiovascular benefits of influenza vaccination
Standard Letter	Behavioral Economic Principles	This group will receive a standard letter on the benefits of influenza vaccination without behavioral economic enhancement
Implementation Intention Prompt Letter	Behavioral Economic Principles	Implementation intention prompt added to the standard letter
Repeated Letter	Behavioral Economic Principles	The standard letter sent out two times instead of once
Respiratory Gain-Framing Letter	Behavioral Economic Principles	Text added to the standard letter highlighting potential respiratory disease-related benefits of influenza vaccination
Loss-Framing Letter	Behavioral Economic Principles	Text added to the standard letter highlighting potential risks of not receiving influenza vaccination

Primary Outcome Measures

Name	Time	Method
Number of participants who received an influenza vaccine	Up to 3 months

Secondary Outcome Measures

Name	Time	Method
Time from intervention delivery to influenza vaccination	Up to 3 months

Trial Locations

Locations (1)

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