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Information Provision to Correct Misperception on Rubella and Promote Antibody Testing and Vaccination: A Nationwide Online Experiment in Japan

Last registered on July 28, 2022

Pre-Trial

Trial Information

General Information

Title
Information Provision to Correct Misperception on Rubella and Promote Antibody Testing and Vaccination: A Nationwide Online Experiment in Japan
RCT ID
AEARCTR-0009703
Initial registration date
July 27, 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
July 28, 2022, 4:30 PM EDT

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

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
In development
Start date
2022-07-20
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 information provision to correct the misperception, “I have rubella antibodies,” affects the uptake of rubella antibody testing and vaccination.

To obtain herd immunity against rubella, Japan must increase the antibody prevalence rate for males born between 1962 and 1978 from 80% to 90%. To accomplish this, following request from the Ministry of Health, Labor, and Welfare (MHLW), local governments have mailed free vouchers for rubella antibody testing and vaccination to men of the target generation from FY2019 to FY2021. However, as of October 2021, the number of vaccination remained low at around 740,000 (about 39% of the target number of vaccination). Thus, the MHLW decides to re-distribute free vouchers also in FY2022. The vouchers 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 the target generation of this policy.

Taking the results of our preliminary survey into account, we found that the subjects could form misperceptions, 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, nor 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 create a flyer to correct these misconceptions and conduct a nationwide online experiment to evaluate its effectiveness.

We will conduct the online experiment in July-August 2022 (N=7,500), with two follow-ups in September 2022 and March 2023 to ascertain the impact of information provision on the behaviors of antibody testing and vaccination.
In July-August 2022, we will conduct one supplementary survey (A) to commplement the manupulation check in the main experiment (N=750). In addition, we will conduct another supplementary survey (B) to measure the demand for the information to correct the misperceptions (N=500).
External Link(s)

Registration Citation

Citation
Kato, Hiroki, Fumio Ohtake and Shusaku Sasaki. 2022. "Information Provision to Correct Misperception on Rubella and Promote Antibody Testing and Vaccination: A Nationwide Online Experiment in Japan." AEA RCT Registry. July 28. https://doi.org/10.1257/rct.9703
Experimental Details

Interventions

Intervention(s)
We have six interventions, and the first three interventions are related to the content of the provided information: (I1, control) no information, (I2) providing basic information, and (I3) providing information to correct people's misperception, in addition to the basic information.

The second three interventions are related to how to provide the information: (P1) providing the information compulsorily, (P2) allowing people to choose whether or not to browse it, and (P3) allowing people to choose whether or not to browse it, while showing a message highlighting the possibility of people's misperception.
Intervention Start Date
2022-08-01
Intervention End Date
2023-03-31

Primary Outcomes

Primary Outcomes (end points)
(1) Whether you are willing to receive the rubella antibody testing and vaccination (binary);
(2) Whether you receive the rubella antibody testing and vaccination (binary)
Primary Outcomes (explanation)
To evaluate the effectiveness of our interventions, we use two primary outcomes, which are obtained from the main online experiments, including two follow-ups.

Secondary Outcomes

Secondary Outcomes (end points)
(1) Willingness-to-pay (and willingness-to-accept) to receive the rubella antibody testing and vaccination (continuous), and willingness to receive receive the rubella antibody testing and vaccination (4 point scale);
(2) Correct answers to quizzes about rubella and the rubella free vouchers (binary), and confidence for answers (5 point scale);
(3) Subjective probability of infection to rubella (0-100%);
(4) Memories of the infection and vaccination of rubella, chickenpox, and measles (binary);
(5) Willingness-to-pay to receive our original flyer
Secondary Outcomes (explanation)
We conduct manipulation check of our interventions on the information provision, using the data from the main online experiment and Supplementary Survey A and the secondary outcomes (2)-(4). We also estimate average demand of our informational intervention, using the data from Supplementary Survey B and the secondary outcomes (5).

Experimental Design

Experimental Design
We will conduct a screening survey to sample individuals who are the target of the MHLW's additional rubella policy in FY2022. Specifically, through an online survey company, we collect survey participants so that their proportions of age and residential area are consistent with those of a nationally representative sample. The screening survey includes the questions on sex, date of birth, and whether or not they have received rubella antibody testing in the past three years. Then, we will limit the sample to males aged 43-60 who have not yet received antibody testing.

The main online experiment creates six experimental arms by combining interventions on the information's content and how to provide it. (I1) is a control. The five treatment groups are (I2*P1), (I3*P1), (I2*P2), (I3*P2), and (I3*P3).
Supplemental Survey A uses the three experimental arms, (I1), (I2*P1), and (I3*P1). Supplemental Survey B has an incentivized multiple price list experiment to measure the demand for our informational intervention. One participant joins only either of the three surveys.
Experimental Design Details
Not available
Randomization Method
The online survey company perform stratified randomization. They use the information on two age groups (43-50 and 51-60) and ten regions, create 20 stratifications, and assign respondents to the experimental arms within each stratification randomly.
Randomization Unit
Individual
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
7,500 in the main online experiment (after two follow-ups, sample size will be less than 7500 due to attrition).
750 in the Supplementary Survey A, and 500 in the Supplementary Survey B.
Sample size: planned number of observations
7,500 in the main online experiment (after two follow-ups, sample size will be less than 7500 due to attrition). 750 in the Supplementary Survey A, and 500 in the Supplementary Survey B.
Sample size (or number of clusters) by treatment arms
Around 1,250 in each experimental arm in the main online experiment.
Around 250 in each experimental arm in the Supplementary Surveys A and B.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
We calculate MDESs for a two-sided hypothesis test with statistical significance of 0.05 and statistical power of 0.8. In the main online experiment, MDES for difference-in-mean is 0.1121 standard deviation.
IRB

Institutional Review Boards (IRBs)

IRB Name
Graduate School of Economics, Osaka University IRB
IRB Approval Date
2022-07-14
IRB Approval Number
R40714
IRB Name
Center for Infectious Disease Education and Research, Osaka University IRB
IRB Approval Date
2022-07-08
IRB Approval Number
2022CRER0708
Analysis Plan

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