Justification of the COVID-19 vaccine distribution: Contested inclusiveness in essential resource allocation

Last registered on February 09, 2022


Trial Information

General Information

Justification of the COVID-19 vaccine distribution: Contested inclusiveness in essential resource allocation
Initial registration date
October 06, 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
October 07, 2021, 7:02 PM EDT

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

Last updated
February 09, 2022, 12:46 AM EST

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



Primary Investigator

The University of Tokyo

Other Primary Investigator(s)

PI Affiliation
The University of Tokyo
PI Affiliation
The University of Tokyo

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
The COVID-19 pandemic is a challenge to all global communities. To overcome it, successful cooperation is critical. At the same time, essential resources such as safe and effective vaccines against COVID-19 and intensive care units in hospitals are scarce resources. For a nation to survive, such scarce resources should be available to all residents, including foreigners. However, the competition of individuals for scarce resources might lead to deepened social divides. Whether a nation can distribute scarce resources in a manner considered optimal for society as a whole, overcoming the conflicts of individual interests, would be an informative measure of that nation's inclusiveness, an ability that affects its survival.

Our experiment is set amid the natural experimental environment of the COVID-19 pandemic in Japan. Japan's capacity for vaccine production is still tightly limited as emergent variants of COVID-19 might necessitate three or more doses of a vaccine. We investigate whether respondents want to allocate COVID-19 vaccines equally among residents of Japanese and foreigners with the same background characteristics, in accord with standards that the government has applied.

We employ a randomized conjoint design. Respondents are shown three hypothetical COVID-19 vaccine recipients, each with different background characteristics, including nationality and residency status. We then asked the respondents to place three potential recipients in order of priority allocation. We observe a marginal change in the preferred allocation of vaccines when nationality and/or residency status is changed.
External Link(s)

Registration Citation

Iida, Takashi, Keisuke Kawata and Masaki Nakabayashi. 2022. "Justification of the COVID-19 vaccine distribution: Contested inclusiveness in essential resource allocation." AEA RCT Registry. February 09. https://doi.org/10.1257/rct.8105-1.2000000000000002
Experimental Details


We adopt a factorial design as a randomized conjoint design. We employ 15,000 respondents in our internet-based experiment and task them with performing a randomized conjoint experiment. In each case, respondents are shown three hypothetical COVID-19 vaccine recipients with different background characteristics, including nationality and residency status. Among those hypothetical recipients, the Japanese nationality is fixed. We then observe whether and how a change in the nationality of a hypothetical recipient affects the respondent's selection of the person in relation to recipients with the same and different background characteristics.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
The outcome of the greatest interest is whether foreign nationality affects respondents' preferences regarding hypothetical vaccine recipients, and, if so, whether the difference in preferences between foreign nationality and own nationality is correlated with geopolitical tension with the home country. If respondents are perfectly rational in their wish to build herd immunity, there should be no discrimination regarding nationality and geopolitical tension with the home country. If there is discrimination on those grounds, this can be a measure of the degree of ethnic and geopolitical distortion shared by Japanese adults facing the pandemic challenges.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We implement a randomized conjoint experiment using 15,000 randomly selected Japanese adult respondents. We assign each respondent 5 tasks; in each, they are asked to place three hypothetical vaccine recipients (whose occupation, age, residency status, family composition, and nationality are randomly combined except that one of the three choices is always Japanese) in order of priority. Responses to Japanese recipients are our control group, and responses to the other recipients are our treatment group.

We collect information about the background characteristics of the 15,000 respondents such as gender, age, prefecture, work status, political preferences, partisanship, income, household income, education, whether reading a newspaper, Internet news, or books, and self-perception of social class. Using a generalized random forest algorithm, we look at whether the effects of the intervention differed based on the background characteristics of the respondents.
Experimental Design Details
Randomization Method
We implement a randomized conjoint experiment. Randomization is performed by a computer of the survey company with which we contract.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
15,000 individuals.
Sample size: planned number of observations
15,000 individuals.
Sample size (or number of clusters) by treatment arms
(15,000 individuals) X (5 choice tasks) X (3 ordered preferences)
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Ethical Review Board, Institute of Social Science, The University of Tokyo.
IRB Approval Date
IRB Approval Number


Post Trial Information

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Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials