A Randomized Controlled Trial Testing the Efficacy of Humor and Framing in Messaging to Correct Misperceptions About COVID-19 Vaccines
Phase: NA
Conditions: Beliefs
Sponsor: Johns Hopkins Bloomberg School of Public Health

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A Randomized Controlled Trial Testing the Efficacy of Humor and Framing in Messaging to 
Correct Misperceptions About COVID-19 Vaccines 
 
NCT05085613 
 
IRB approved 8/4/2021 

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Abstract: More than one million people in the United States have died from COVID-19-related 
complications.1  Despite vaccine availability, as of June 2022, approximately 9% of the eligible adult 
population hadn’t received a single dose of the COVID vaccine, and in some states rates of having gotten 
at least one dose are as low as 71%.1   The unvaccinated and under-vaccinated remain more susceptible to 
severe outcomes from COVID, including hospitalization and death.2 Vaccine hesitancy is partially driven 
by misperceptions, including the belief that they are not safe, and not effective.3 Identifying strategies to 
correct this misperception may potentially increase vaccine uptake. Correcting misperceptions, however, 
is not a straightforward process, and often fails due to the Continued Influence Effect (CIE).  The CIE 
occurs when misinformation in memory continues to influence inferences and decisions even after 
correction, which presents a barrier to misperception correction.4 Additional communication strategies 
can also be considered. As Conservatives have lower rates of vaccination,5 framing the consequence of 
vaccination to resonate with conservative values like freedom (i.e. If you get vaccinated, you’ll have the 
freedom to engage in social activities) and economic recovery (i.e. If you get vaccinated, businesses can 
stay open and Americans can keep working and supporting their families)6,7 has the potential to increase 
message efficacy and reduce reactance by aligning the message with the readers values.8,9 Likewise, there 
is evidence that humor can improve message efficacy. Humor can increase attention, message liking, and 
can produce positive affect that may reduce reactance and motivate effortful message processing.10–12 
 
 
Objectives: This study tests the efficacy of adding a freedom consequent frame, an economic recovery 
consequent frame, or humor to a coherent corrective message in a randomized controlled experiment to 
compare their efficacy to a message that is coherent, but does not include a frame or humor.  Outcomes 
include beliefs that FDA-authorized vaccines are safe and effective (e.g. an indicator of message recall 
and acceptance due to surface updating) and inferential beliefs about the safety and effectiveness of other 
vaccines that either did or did not received FDA authorization. These related concepts test whether 
participants updated their mental models of FDA review and can use these updated models to make 
inferences when asked about the safety and effectiveness of other vaccines (e.g. an indicator of updated 
conceptual understanding via global updating).   
 
 
 
Background: The persistence of misperception has been noted in other disciplines, including cognitive 
psychology and political science. Many experiments in these fields have demonstrated that exposure to 
corrective information can elicit correct recall of the corrective information, however, misinformation is 
often still used to make inferences about related topics, which has come to be known as the Continued 
Influence Effect (CIE).4,13,14 It has been theorized that, when presented with corrective messaging, 
individuals may engage in ‘surface updating’ (the individual updates only the specific misperception 
addressed in the message), but fail to engage in ‘global updating’ (fully integrating information into 
beliefs so it can be applied via inferential reasoning and behavioral decisions).4,13,14 Thus, it is possible 
that after exposure to corrective information about nicotine, an individual could accurately state that 
nicotine is not the main cancer-causing constituent in tobacco (surface updating), yet fail to accurately 
characterize the relative harm of a non-combustible nicotine-containing product when compared to a 
combustible cigarette if that product was not discussed in the message (global updating).15 This study 
combines typical corrective strategies with framing and humor to assess effects on misperceptions about 
the COVID vaccines, 
 
Study Procedures 
 
Participants were recruited online using Amazon Mechanical Turk. After clicking on the tasks, 
participants first consented to answering questions on a screening questionnaire to determine eligibility. 
Eligible participants then read an informed consent for the experiment. After agreeing to participate, 
participants were asked questions about their sociodemographic characteristics, beliefs, behaviors, and 

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behavioral intentions about the COVID vaccines. Participants were then randomized to view one of four 
messages using a 1:1:1:1 ratio using the “evenly present elements” option in Qualtrics. All messages had 
similar information about the COVID vaccines safety and effectiveness. One message had an economic 
recovery frame, one had a freedom frame, one included humor, and the control didn’t include a frame or 
humor. As randomization was conducted in Qualtrics, both experimenters and participants were blinded 
to randomization. After message exposure, participants answered questions about the message and their 
beliefs and intentions to get a COVID vaccine. The survey took between 10-15 mins to complete. The 
study protocol was approved by the Institutional Review Board at the Johns Hopkins Bloomberg School 
of Public Health on August 4, 2021 (IRB00015120). No participants were removed while the study was 
ongoing, but responses that showed signs of being repeat responders or bots (according to metrics from 
survey platform Qualtrics) were later dropped from analysis. 
 
Inclusion Criteria 
1. 21 years of age or older 
2. Not yet received a COVID vaccine 
3. Not completed the cognitive interview during message development 
4. Rated agreement with the following statement as less than or equal to 50 out of 100: “The FDA has 
only authorized COVID vaccines that are safe and effective” 
 
Exclusion Criteria  
1. Under the age of 21. 
2. Had already received a COVID vaccine 
3. Had completed a cognitive interview during message development. 
4. Rated agreement with the following statement as greater than 50 out of 100: “The FDA has only 
authorized COVID vaccines that are safe and effective” 
 
Study Statistics 
a. Primary outcome variable 
 
1. Change in Accuracy of the Belief That FDA Authorized COVID-19 Vaccines Are Safe and 
Effective  
2. Accuracy of Inferential Belief That the FDA Authorized Flu Vaccine is Safe and Effective  
3. Accuracy of Inferential Belief That RexVax is Safe and Effective  
4. Change in Intention to Get a COVID-19 Vaccine  
 
Statistical plan: Stata version 15 was used for all statistical analyses. Participant characteristics are 
reported as sample proportions and counts for categorical variables and median and interquartile range for 
continuous variables due to skewed distributions. Fisher’s exact tests were used to assess balancing across 
conditions by categorical variables to account for the small sample size (e.g. cell sizes with n<10).85 Non-
parametric Kruskal-Wallis tests were used to assess differences in continuous variables to assess 
balancing by condition. Fisher’s exact test was also used to assess differences in response to manipulation 
check questions by condition. Kruskal-Wallis tests were used to assess differences in perceived message 
credibility and campaign targeted knowledge by condition. Repeated measures t-tests were used to assess 
the significance of an overall unadjusted change in belief that COVID vaccines are safe and effective 
between pre and post message exposure (H1). ANCOVAs were used to assess if there was a difference by 
message condition and 1. Accuracy of belief that FDA-authorized COVID vaccines are safe and effective 
(H2), 2. Accuracy of inferential beliefs about the safety and effectiveness of FDA-authorized flu vaccines 
(H3), and 3. Accuracy of inferential beliefs about the safety and effectiveness of ResVax, which did not 
receive FDA authorization (H4).  Baseline belief that the COVID vaccines were safe and effective, race, 
sex, geographic region, and political affiliation were a priori included as covariates in ANCOVA 1. Race, 
highest educational attainment, sex, geographic region, and political affiliation were included as a priori 
covariates in ANCOVAs 2 and 3. Covariates were selected based on their association with vaccine 

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perceptions in extant literature. Message recall was not included in ANCOVAs because most participants 
had perfect recall, there were no differences observed in message recall by condition, and including of 
recall in ANCOVAs did not improve model fit.  When condition was significant at p<.05, pairwise 
comparisons comparing each experimental condition (economic recovery, humor, freedom), to the control 
condition were made using Sidak’s adjustment, which is slightly less conservative than Bonferroni and 
appropriate to control the type I error rate during pairwise comparisons after an ANCOVA when the 
sample size between groups is not equal. 
 
Risks 
a. Risks were minimal and included boredom of discomfort from answering survey questions. 
b. To mitigate this risk, participants read in the informed consent that they were free to skip any 
questions they didn’t want to answer or quit their participation at any time. 
c. There were no unanticipated problems or deviations during data collection. 
 
Benefits 
a. 
Participants did not participate directly from being in the study. Findings can help to 
inform what kind of messaging might be helpful to adults who were hesitant to get the 
COVID vaccine to help correct misperceptions and increase intention to get vaccinated.  
 
Payment and Remuneration 
a. 
Participants were paid $5.00 for completing the survey. Participants who were eligible 
but did not fully complete the survey were still paid.  
Costs 
a. 
No costs were associated with participation.  
 
 
 
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