AEA RCT Registry

Trial Information

General Information

Title

Situation-dependent willingness to pay for the Covid-19 vaccine: Infection stage, peers, and nudges

RCT ID

AEARCTR-0007056

Initial registration date

January 15, 2021

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 15, 2021, 7:17 AM EST

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

Last updated

March 21, 2022, 1:12 AM EDT

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

Locations

Country

Japan

Region

Primary Investigator

Name

Shusaku Sasaki

Affiliation

Tohoku Gakuin University

Contact Primary Investigator

Other Primary Investigator(s)

PI Name

Tomoya Saito

PI Affiliation

National Institute of Infectious Diseases

PI Name

Fumio Ohtake

PI Affiliation

Osaka University

Additional Trial Information

Status

On going

Start date

2021-01-18

End date

2025-03-31

Keywords

Behavior, Health

Additional Keywords

Covid-19, Vaccine Avoidance, Willingness to Pay, WTP, Vaccination Behavior, Nudge, Time Preference, Risk Preference, Social Preference, Health Economics, Behavioral Economics, Survey Experiment, Japan

JEL code(s)

Secondary IDs

Prior work

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

Abstract

We study the levels and characteristics of people's willingness-to-pays (WTPs) for the Covid-19 vaccine under various situations, by conducting a survey experiment on a nationwide sample in Japan and using multiple hypothetical questions with Multiple Price List formats. Specifically, we conduct the following three studies. In Study 1, we examine how the levels of the WTPs change according to vaccine effectiveness, infection stage, and vaccination progress. We then conduct a follow-up survey, capture their actual vaccination behavior, and clarify the correlation between their WTPs and vaccination behavior. In Study 2, we examine how the WTPs are influenced by nudge-based messages emphasizing selfish or altruistic benefits of the vaccination. In Study 3, we compare the levels and characteristics of the WTPs between young people (25-39 years old) and elderly people (60-74 years old). We further explore how the WTPs’ differences depend on the distributions and parameters of the variables of socio-economic attributes and behavioral economic and psychological characteristics, including time preferences, risk preferences, social preferences, and subjective risks.

External Link(s)

Registration Citation

Citation

Sasaki, Shusaku, Fumio Ohtake and Tomoya Saito. 2022. "Situation-dependent willingness to pay for the Covid-19 vaccine: Infection stage, peers, and nudges." AEA RCT Registry. March 21. https://doi.org/10.1257/rct.7056

Sponsors & Partners

Experimental Details

Interventions

Intervention(s)

We conduct an online survey experiment and randomly assign the survey respondents to either of one control group and two treatment groups. One treatment group provides a message emphasizing selfish benefits of vaccination, while another treatment group provides a message emphasizing its social (altruistic) benefits.

Intervention Start Date

2021-01-18

Intervention End Date

2021-01-20

Primary Outcomes

Primary Outcomes (end points)

Willingness to pay for the Covid-19 vaccine (in the initial main survey)

Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)

Willingness to pay and self-reported vaccination behavior (in the follow-up surveys)

Secondary Outcomes (explanation)

Experimental Design

We conduct an online survey experiment and randomly assign the survey respondents to either of one control group and two treatment groups. One treatment group provides a message emphasizing selfish benefits of vaccination, while another treatment group provides a message emphasizing its social (altruistic) benefits.

Experimental Design Details

Not available

Randomization Method

Stratified randomization by a survey company. The strata are based on age, gender, and place of residence.

Randomization Unit

Individuals

Was the treatment clustered?

No

Experiment Characteristics

Sample size: planned number of clusters

N/A

Sample size: planned number of observations

12,000 individuals (at maximum)

Sample size (or number of clusters) by treatment arms

6,000 individuals in the control group, 3,000 individuals in the selfish-message group, and 3,000 individuals in the altruistic-message group (respectively at maximum)

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

Supporting Documents and Materials

IRB

Institutional Review Boards (IRBs)

IRB Name

Graduate School of Economics, Osaka University IRB

IRB Approval Date

2021-01-04

IRB Approval Number

N/A

Analysis Plan