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Heard immunity: effective messaging for a future COVID-19 vaccine
Initial registration date
July 09, 2020
July 10, 2020 10:01 AM EDT
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Sol Price School of Public Policy/USC
Other Primary Investigator(s)
Additional Trial Information
This study uses a survey experiment to determine the most effective messaging to persuade people to take up a future vaccine for COVID-19. Ending the pandemic necessitates enough vaccination to achieve herd immunity, but survey evidence suggest up to 50% of people are hesitant to vaccinate. The survey divides respondents into one control and four treatment groups. Each treatment group is exposed to a message emphasizing either the benefits of vaccination or the risks of avoiding vaccination, to the respondent personally or to society in general. The survey is administered by USC's Understanding America Survey to a nationally representative panel. The outcome measure of interest is differences in self-reported intention to vaccinate for the four treatment arms relative to control, using a means-comparison test with inference adjusted for the testing of four hypotheses.
Intervention Start Date
Intervention End Date
Primary Outcomes (end points)
Self-reported intention to vaccinate against COVID-19 in the future
Primary Outcomes (explanation)
Respondents are asked whether they want the coronavirus vaccine when it becomes available. I code "Yes" as 1 and "No" or "I don't know / Not sure" as 0.
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design Details
Was the treatment clustered?
Sample size: planned number of clusters
Sample size: planned number of observations
Sample size (or number of clusters) by treatment arms
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
effect size 30% standard deviation is rejected 80% of the time.
INSTITUTIONAL REVIEW BOARDS (IRBs)
University of Southern California Institutional Review Board
IRB Approval Date
IRB Approval Number