Nationwide Utilization of Danish Government Electronic Letter System for Increasing InFLUenza Vaccine Uptake

Study Overview
=================
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. 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.

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.

Official Title
-----------------
Nationwide Utilization of Danish Government Electronic Letter System for Increasing InFLUenza Vaccine Uptake

Conditions
-----------------
Influenza, Behavior and Behavior Mechanisms

Intervention / Treatment
-----------------
* Behavioral: Behavioral Economic Principles


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Age >=65 years at January 15, 2023 (eligible for free influenza vaccination in the official Danish vaccination program) Access to the official, mandatory Danish electronic mailbox system Exclusion Criteria: 1) Persons living in nursing homes

Ages Eligible for Study
-----------------
Minimum Age: 65 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

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


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Control<br>No letter | |
| Experimental: Standard Letter<br>This group will receive a standard letter on the benefits of influenza vaccination without behavioral economic enhancement | Behavioral: Behavioral Economic Principles<br>* 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.<br>|
| Experimental: Priming & Hot State Activation - 1 reminder<br>The standard letter sent out two times instead of once | Behavioral: Behavioral Economic Principles<br>* 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.<br>|
| Experimental: Depersonalized Letter<br>The standard letter without the recipient's name | Behavioral: Behavioral Economic Principles<br>* 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.<br>|
| Experimental: Gain-Framing/Context<br>Text added to the standard letter employing the specified behavioral economic principle | Behavioral: Behavioral Economic Principles<br>* 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.<br>|
| Experimental: Loss-Framing/Context<br>Text added to the standard letter employing the specified behavioral economic principle | Behavioral: Behavioral Economic Principles<br>* 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.<br>|
| Experimental: Collective Goal<br>Text added to the standard letter employing the specified behavioral economic principle | Behavioral: Behavioral Economic Principles<br>* 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.<br>|
| Experimental: Active Choice/Implementation Intention Prompt<br>Text added to the standard letter employing the specified behavioral economic principle | Behavioral: Behavioral Economic Principles<br>* 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.<br>|
| Experimental: Cardiovascular Gain Frame<br>Text added to the standard letter employing the specified behavioral economic principle | Behavioral: Behavioral Economic Principles<br>* 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.<br>|
| Experimental: Expert Authority<br>Text added to the standard letter employing the specified behavioral economic principle | Behavioral: Behavioral Economic Principles<br>* 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.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

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

Secondary Outcome Measures

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

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Influenza, Vaccination, Nudging, Behavioral Science