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

Tor Biering-Sørensen

Status: Active, not recruiting

Conditions: Influenza; Behavior and Behavior Mechanisms

Treatments: Behavioral: Behavioral Economic Principles

Study type: Interventional

Funder types: Other

Identifiers

NCT06600490

NUDGE-FLU-CHRONIC-2

Details and patient eligibility

About

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 2023/2024 influenza season, the first NUDGE-FLU-CHRONIC trial demonstrated the effectiveness of behavioral nudging letters in increasing influenza vaccination rates among adults aged 18-64 years with chronic diseases in Denmark. 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 adults aged 18-64 years with chronic diseases including whether the effectiveness of the previously successful strategies can be confirmed during a subsequent influenza season.

Full description

The study is a prospective, randomized, open-label implementation trial. The study population will consist of persons aged 18-64 years identified as eligible for free-of-charge influenza vaccination due to a chronic condition. Subjects will be identified through Danish nationwide health registries using codes from the International Classification of Diseases, 10th revision (ICD-10). 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.

Enrollment: 308,978 patients

Sex: All

Ages: 18 to 64 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

1. Age 18-64 years

2. Must be registered in the Danish nationwide registries as meeting at least one of the following eligibility criteria for free-of-charge influenza vaccination in the Danish public health system:

   1. Chronic lung disease
   2. Chronic cardiovascular disease other than hypertension
   3. Type 1 or type 2 diabetes mellitus
   4. Congenital or acquired immunodeficiency
   5. Impaired breathing due to muscular weakness
   6. Chronic renal or hepatic insufficiency
   7. Other chronic conditions with an increased risk of severe influenza as determined by the treating physician

3. Access to the official, mandatory Danish electronic mailbox system

Exclusion criteria

None

Trial design

Primary purpose: Other

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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308,978 participants in 7 patient groups

Usual Care

No Intervention group

Description:

No letter

Standard Letter

Experimental group

Description:

This group will receive a standard letter on the benefits of influenza vaccination without behavioral economic enhancement

Treatment:

Behavioral: Behavioral Economic Principles

Repeated Letter

Experimental group

Description:

The standard letter sent out two times instead of once

Treatment:

Behavioral: Behavioral Economic Principles

Cardiovascular Gain-Framing Letter

Experimental group

Description:

Text added to the standard letter highlighting potential cardiovascular benefits of influenza vaccination

Treatment:

Behavioral: Behavioral Economic Principles

Repeated Cardiovascular Gain-Framing Letter

Experimental group

Description:

The cardiovascular gain-framing letter sent out two times instead of once

Treatment:

Behavioral: Behavioral Economic Principles

Respiratory Gain-Framing Letter

Experimental group

Description:

Text added to the standard letter highlighting potential respiratory disease-related benefits of influenza vaccination

Treatment:

Behavioral: Behavioral Economic Principles

Implementation Intention Prompt Letter

Experimental group

Description:

Implementation intention prompt added to the standard letter

Treatment:

Behavioral: Behavioral Economic Principles