Vaccine information provision

Last registered on December 09, 2025
View Trial History

Pre-Trial

Trial Information

General Information

Title
Vaccine information provision
RCT ID
AEARCTR-0017358
Initial registration date
December 02, 2025

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
December 09, 2025, 7:23 AM EST

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

Locations

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Primary Investigator

Name
Daniel Sacks
Affiliation
Contact Primary Investigator

Other Primary Investigator(s)

Additional Trial Information

Status
On going
Start date
2025-11-25
End date
2026-03-01
Keywords
Health
Additional Keywords
JEL code(s)
Secondary IDs
AsPredicted #260276
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
no information provided to avoid informing trial participants
External Link(s)

Registration Citation

Citation
Sacks, Daniel. 2025. "Vaccine information provision." AEA RCT Registry. December 09. https://doi.org/10.1257/rct.17358-1.0
Sponsors & Partners

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Experimental Details

Interventions

Intervention(s)
kept private to avoid biasing the study
Intervention Start Date
2025-12-02
Intervention End Date
2025-12-08

Primary Outcomes

Primary Outcomes (end points)
Our primary outcome variable is the believed, personal side effect rate of vaccination. We ask people to imagine they do not vaccinate tomorrow - what is the percentage point likelihood that they experience one or more severe adverse events over the next few days. This is the "posterior_no_vacc." Next we ask people the same question but imagining that they DO vaccinate. This is the "posterior_vacc" Our key dependent variable, the believed side effect rate, is posterior_vacc minus posterior_no_vacc.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
various measures of vaccine intentions, plus persistence in beliefs and reliability of the provided information
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
kept private to avoid biasing the study
Experimental Design Details
Not available
Randomization Method
qualtrics randomizer
Randomization Unit
individual
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
4000
Sample size: planned number of observations
4000
Sample size (or number of clusters) by treatment arms
4000
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Simulations on pilot data indicate an MDE of just over 2.9 percentage points, with 80% power. The SD of the unadjusted outcome metric is 31.6 and the mean is 19.6, so the MDE is 15% of the mean.
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
University of Wisconsin IRB
IRB Approval Date
2025-10-27
IRB Approval Number
2025-1542
Analysis Plan

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