#90134 | AsPredicted

'Vaccine Metascience Summaries'
(AsPredicted #90134)

Created:       03/07/2022 11:47 AM (PT)

This is an anonymized version of the pre-registration.  It was created by the author(s) to use during peer-review.
A non-anonymized version (containing author names) should be made available by the authors when the work it supports is made public.

1) Have any data been collected for this study already?
No, no data have been collected for this study yet.

2) What's the main question being asked or hypothesis being tested in this study?
We developed a webpage that contains metascientific information about COVID-19 vaccine safety research, to target three broad persona groups: deferrers, unconcerned, and rejecters. We hypothesize:

Main hypothesis: Displaying metascientific information about covid vaccine research will improve participants' awareness, trust (this effect strongest for rejecters) and perceived consensus of vaccine safety research, perceived safety of the vaccine, and intention to get vaccinated (this effect strongest for deferrers.

Additionally, we expect that providing information about the danger of covid and vaccine efficacy in addition to vaccine safety will be more effective at convincing rejecters and unconcerned to get vaccinated than safety information alone

3) Describe the key dependent variable(s) specifying how they will be measured.
Using survey questions, we will measure 1) participants' perceived % risk of having a serious adverse reaction following a COVID-19 vaccination (multi-choice, pre-post), 2) participants' belief in the safety of the vaccine, worries about covid, efficacy of the vaccine, and cost of the vaccine (likert scale, pre-post) 3) participants' intention to get vaccinated ("definitely/maybe/definitely not", pre-post), 4) credibility of vaccine research (3 likert scale questions for trustworthiness, competence, and benevolence, pre-post), 5) change in perceived amount, consistency, and direction of vaccine research after viewing intervention (3 likert questions, post), and 6) perceived number of research teams who've studied covid vaccine safety (multi-choice, post)

4) How many and which conditions will participants be assigned to?
There will be three conditions. 1) One where participants read information from the CDC page on COVID vaccines ("baseline"), 2) one where they read our webpage providing metascientific information about vaccine safety research ("safety-only"), 3) one identical to 2), but with the addition of a visualization describing the dangers of COVID, and the positive effects of the vaccine ("covid-risk").

5) Specify exactly which analyses you will conduct to examine the main question/hypothesis.
To separate participants into our three persona groups, we will first separate participants who have not yet been fully vaccinated, and who answered "maybe" or "definitely not" when asked whether they would get their next vaccine dose. Those who answered that they still haven't decided whether to get the vaccine, and agree with the statement "I need to wait for more data before deciding whether or not the vaccine is safe." will be considered deferrers. Those who agree with the statement "I'm not worried about getting infected with COVID." will be considered unconcerned. Those who state they will definitely not get vaccinated, and agree with the statement "I don't trust the people and institutions that created, tested, and deployed the COVID-19 vaccines." will be considered rejecters. All others will be considered unclassified.

We will use ANOVAs to test our hypotheses, except for vaccine intention, where we will use ordinal regression with participant ID as a random effect and time (i.e. pre-post) as an interaction, or knowledge questions (vax risk and number of teams), where we will do the same but with logistic regression. We will use Dunnett's test for pairwise comparisons of both experimental conditions against the baseline condition, except when testing the above regressions. There, we will use a Z-test to compare the relative strengths of the ordinal regression coefficients of both experimental conditions, using the control condition as a baseline.

Where appropriate, these tests will also be separated by participant group. We will test participant identity as a deferrer as an interaction term when testing whether the "safety-only" condition affects vaccine intention, as well as test the interaction between being unconcerned or a rejector on the effects of the "covid-risks" condition on vaccine intention. We will also test the interaction between being a rejector and both experimental conditions on participants' trust of vaccine researchers.

Finally, we will test a SEM specifying that trust in vaccine research, perception of the amount of research, and perception of the consistency of research will positively affect participants' beliefs in the safety of the COVID-19 vaccines, which will in-turn affect their intention to get vaccinated. We may test variations of this model, particularly if the model as specified shows poor fit, in which case they will be considered exploratory analyses.

6) Describe exactly how outliers will be defined and handled, and your precise rule(s) for excluding observations.
Will not analyze data from participants who did not spend enough time (i.e. 15 seconds) on the page where the manipulation is shown, or who fail our attention check.

7) How many observations will be collected or what will determine sample size?
No need to justify decision, but be precise about exactly how the number will be determined.

We will collect a sample of n=350 per cell (total N=1050), slightly oversampling given a power analysis assuming a low (f=0.1) effect size at 80% power. We will continue sampling until we achieve this size (after excluding participants as per 6) or we hit our budget constraints.

8) Anything else you would like to pre-register?
(e.g., secondary analyses, variables collected for exploratory purposes, unusual analyses planned?)

Nothing else to pre-register.