Applying Behavioral Insights to Rubella Antibody Testing and Vaccination: A Field Experiment in Kanagawa, Japan

Last registered on June 19, 2022

Pre-Trial

Trial Information

General Information

Title
Applying Behavioral Insights to Rubella Antibody Testing and Vaccination: A Field Experiment in Kanagawa, Japan
RCT ID
AEARCTR-0009454
Initial registration date
June 12, 2022

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
June 15, 2022, 10:15 AM EDT

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

Last updated
June 19, 2022, 8:09 PM EDT

Last updated is the most recent time when changes to the trial's registration were published.

Locations

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Primary Investigator

Affiliation
Graduate School of Economics, Osaka University

Other Primary Investigator(s)

PI Affiliation
Center for Infectious Disease Education and Research, Osaka University
PI Affiliation
Center for Infectious Disease Education and Research, Osaka University

Additional Trial Information

Status
On going
Start date
2022-06-17
End date
2025-03-31
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
This study will reveal how sending nudge-based messages to correct the false belief “I have antibodies for rubella” affects the uptake of rubella antibody testing and vaccination.

In Japan, herd immunity to rubella can be obtained by achieving a 90% antibody prevalence rate for rubella in all generations. While the rate has reached over 90% among most generations, the rate for males born between 1962 and 1978 is approximately 80%, because they were previously excluded from the routine vaccinations and had few natural infections. Therefore, the Ministry of Health, Labor, and Welfare (MHLW) has set a policy goal of increasing the antibody prevalence rate of this generation of males from 80% to 90% to obtain herd immunity against rubella.

To achieve this goal, free coupons for rubella antibody testing and vaccination have been mailed to males of the target generation from FY2019 to FY2021 by local governments. The MHLW expected that the policy goal described above could have been achieved if approcimately 1.9 million had used these coupons and received the rubella vaccination. However, as of October 2021, the number of people vaccinated remained low at about 740,000 (about 39% of the target number). Therefore, the MHLW decides to re-distribute free coupons starting also in FY2022. The coupons will be mailed to males born between 1962 and 1978 who have not received an antibody testing during FY2019 to FY2021, or who have not been vaccinated even though they are eligible for the vaccination.

Taking the results of our preliminary survey into account, we find that the subjects could form false beliefs, such as “I received the rubella vaccine when I was a child" (even though there were no routine rubella vaccinations for their generations) or “I was infected with rubella in the past" (even though they was actually infected with chickenpox or measles, not rubella). We focus on the possibility that these misperceptions may be a bottleneck of preventing them from getting tested and vaccinated. In this study, we will develop a nudge-based message to correct this belief and conduct a field experiment in cooperation with a local government in Kanagawa, Japan, to evaluate the effect of the message.

The subjects of our field experiment are males born between 1962 and 1978 who reside in that local government’s area and who have not yes been tested for rubella antibodies during FY2019 to FY2021 (N=22,526). We stratify the subjects by 13 residential regions and randomly assign them to three groups, including a control group and two treatment groups. The control group will receive coupons and a leaflet developed by the local government, while the two treatment groups will additionally receive nudge-based messages developed by us in two different ways.

We will receive anonymized administrative data from the local government on the date of the antibody test, the result of the antibody test, and the date of vaccination. Our primary outcomes are “antibody testing behavior” and “vaccination behavior”. Using these binary variables, we estimate the average effect of nudge-based interventions on vaccination, e.g., through linear probability models. Our secondary outcomes are “date of antibody test” and “vaccination date,” in addition to “whether the antibody test result was negative.” Using these date variables, we estimate the effect of the interventions on the vaccination date using, for example, a survival analysis.
External Link(s)

Registration Citation

Citation
Kato, Hiroki, Fumio Ohtake and Shusaku Sasaki. 2022. "Applying Behavioral Insights to Rubella Antibody Testing and Vaccination: A Field Experiment in Kanagawa, Japan." AEA RCT Registry. June 19. https://doi.org/10.1257/rct.9454
Experimental Details

Interventions

Intervention(s)
In Japan, local governments mail to males in the targeted generation “coupons,” by which they receive free antibody testing and vaccination against rubella. In general, the local governments send the coupons and other explanatory materials, including a list of medical institutions that offer the testing and vaccination.

In a collaboration with a local government in Kanagawa, Japan, we add the following two interventions to mailings: (1) enclosing a nudge-based flyer into the envelope; (2) printing a nudge-based message on the envelope.
Intervention Start Date
2022-06-17
Intervention End Date
2023-03-31

Primary Outcomes

Primary Outcomes (end points)
(1) Whether or not you received the rubella antibody testing (binary);
(2) Whether or not you have received the rubella vaccination (binary)
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
(1) Binary variable of whether the antibody test result is negative (i.e., whether vaccination is required);
(2) When you received the rubella antibody testing (date);
(3) When you received the rubella vaccination (date).
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
In addition to a control group, we use the two interventions to create two treatment groups, including Nudge A and Nudge B. Nudge A group will receive only one intervention, “enclosing a nudge-based flyer.” The Nudge B group will receive two interventions, “printing a nudge-based message on envelop” and “enclosing a nudge-based flyer.”

All the three groups will receive the groups and other explanatory materials, including a list of medical institutions that offer the testing and vaccination, while only the control group will receive no nudge-based intervention.

Before starting the experiment, we receive from the local government a list of the target population for MHLW’s FY2022 measures against rubella in order to conduct random assignment. The data contains information on individual ID, age, and region of residence. The target population for MHLW’s FY2022 measures against rubella is not only (a) those who have not received either antibody testing or vaccination, but also (b) those who have received antibody testing and have not been vaccinated despite negative results. The data can identify the type of subjects.

We employ a stratified randomization method by 13 regions. To begin with, we restrict the experiment to those categorized as the type (a). However, those categorized as the type (b) will receive the same mailings as the control group. Our analysis excludes this group, and we call this group the Exclusion group. We then stratify the subjects according to the 13 regions and randomly assign them to the three groups per region. The allocation ratio is equal among regions. See the Analysis plan for details.
Experimental Design Details
Not available
Randomization Method
Stratified randomization done in office by a computer.
Randomization Unit
Individual.
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
22,526 individuals.
Sample size: planned number of observations
22,526 individuals.
Sample size (or number of clusters) by treatment arms
7,504 individuals in the control; 7,412 individuals in the nudge A; 7,510 individuals in the nudge B.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
MDESs are for a two-sided hypothesis test with statistical significance of 0.05 and statistical power of 0.8. • Control vs. Nudge A: 0.0457 standard deviation • Control vs. Nudge B: 0.0457 standard deviation • Nudge A vs. Nudge B: 0.0457 standard deviation
IRB

Institutional Review Boards (IRBs)

IRB Name
Graduate School of Economics, Osaka University IRB
IRB Approval Date
2022-05-12
IRB Approval Number
R4051
IRB Name
Center for Infectious Disease Education and Research, Osaka University IRB
IRB Approval Date
2022-05-06
IRB Approval Number
2022CRER0506
Analysis Plan

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