Financial incentives for influenza vaccination

Last registered on January 19, 2024

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Pre-Trial

Trial Information

General Information

Title

Financial incentives for influenza vaccination

RCT ID

AEARCTR-0012849

Initial registration date

January 16, 2024

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published

January 19, 2024, 2:13 PM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Locations

Country

United States of America

Region

Primary Investigator

Name

Mireille Jacobson

Affiliation

USC

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Other Primary Investigator(s)

PI Name

Tom Chang

PI Affiliation

USC

Contact Investigator

PI Name

Manisha Shah

PI Affiliation

UC Berkeley

Contact Investigator

Additional Trial Information

Status

In development

Start date

2024-01-17

End date

2024-02-29

Keywords

Health

Additional Keywords

JEL code(s)

Secondary IDs

Prior work

This trial does not extend or rely on any prior RCTs.

Abstract

In this work, we are assessing the impact of messaging with or without a $50 financial incentive on influenza vaccination rates in a county health system. Our main hypothesis is that a message with a $50 financial incentive will increase vaccination rates relative to a control/"treatment as usual" group. We further hypothesize that the financial incentive will increase vaccination rates relative to the message only arm.

External Link(s)

Registration Citation

Citation

Chang, Tom, Mireille Jacobson and Manisha Shah. 2024. "Financial incentives for influenza vaccination." AEA RCT Registry. January 19. https://doi.org/10.1257/rct.12849-1.0

Sponsors & Partners

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Experimental Details

Interventions

Intervention(s)

In this work, we study the impact of an email or SMS message encouraging influenza vaccination with or without the offer of a $50 financial incentive on influenza vaccination rates within 1-week of messaging.

Intervention Start Date

2024-01-17

Intervention End Date

2024-01-25

Primary Outcomes

Primary Outcomes (end points)

Influenza vaccination within 1 week

Primary Outcomes (explanation)

Influenza vaccination as documented in the California Immunization Registry within 1 week

Secondary Outcomes

Secondary Outcomes (end points)

Influenza vaccination within longer periods such as 2 weeks and 1 month

Secondary Outcomes (explanation)

Secondary outcomes will also be based on California Immunization Registry data. We will be able to test for any changes by arm and changes in any differences by arm.

Experimental Design

Empaneled patients or non-empaneled patients with a primary care visit in past 18 months with valid insurance ages 18 and due for a flu shot according to the electronic medical record will be randomized 1:1:1 to 1) receive a message reminding them that it's not too late to get the flu shot along with a link to set up an appointment, 2) receive the same message but with the offer of a $50 Amazon gift card if they are vaccinated within 1-week or 3) to treatment as usual, with no special message. Messaging from the health system continues as usual but does not differ across arms.

Experimental Design Details

Empaneled patients or non-empaneled patients with a primary care visit in past 18 months with valid insurance ages 18 and due for a flu shot according to the electronic medical record will be randomized 1:1:1 across 3 arms. A third will receive a message reminding them that it's not too late to get the flu shot along with a link to set up an appointment, another third will receive the same message but with the offer of a $50 Amazon gift card if they are vaccinated within 1-week and the final third will not receive any special message. Messaging from the health system continues as usual but does not differ across arms.

Randomization Method

In the electronic medical record by the health system.

Randomization Unit

Patient

Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters

None

Sample size: planned number of observations

Approximately 66,000 patients

Sample size (or number of clusters) by treatment arms

Approximately 22,000 patients per arm.

Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

To calculate power we assume a weekly vaccination rate of 1% and use 80% power and 2.5% alpha. We use 2.5% alpha to adjust for the two comparisons in our analysis (message + financial incentive vs. control and message + financial incentive vs. message only. Using these parameters yields a minimum detectable effect of 0.31 percentage points. See analysis plan for MDE at other vaccination rates.

Supporting Documents and Materials

IRB