Effects of side-effect risk framing strategies on COVID-19 vaccine intentions: a randomized controlled trial

  1. Nikkil Sudharsanan
  2. Caterina Favaretti
  3. Violetta Hachaturyan
  4. Till Bärnighausen
  5. Alain Vandormael

  • Curated by eLife

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    Evaluation Summary:

    This randomized clinical trial is based on 8,998 participants from the U.S. and the U.K. to examine the association between risk-framing nudges and the willingness to get a Covid vaccine. This manuscript would be of interest to behavioral scientists, particularly behavioral economists. Findings from this work reveal that (1) nudging can substantially increase the likelihood of Covid vaccination; (2) using different nudging frames matters and may produce different results.

    (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)

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Abstract

Fear over side-effects is one of the main drivers of COVID-19 vaccine hesitancy. A large literature in the behavioral and communication sciences finds that how risks are framed and presented to individuals affects their judgments of its severity. However, it remains unknown whether such framing changes can affect COVID-19 vaccine behavior and be deployed as policy solutions to reduce hesitancy.

Methods:

We conducted a pre-registered randomized controlled trial among 8998 participants in the United States and the United Kingdom to examine the effects of different ways of framing and presenting vaccine side-effects on individuals’ willingness to get vaccinated and their perceptions of vaccine safety.

Results:

Adding a descriptive risk label (‘very low risk’) next to the numerical side-effect and providing a comparison to motor-vehicle mortality increased participants’ willingness to take the COVID-19 vaccine by 3.0 percentage points (p=0.003) and 2.4 percentage points (p=0.049), respectively. These effects were independent and additive and combining both framing strategies increased willingness to receive the vaccine by 6.1 percentage points (p<0.001). Mechanistically, we find evidence that these framing effects operate by increasing individuals’ perceptions of how safe the vaccine is.

Conclusions:

Low-cost side-effect framing strategies can meaningfully affect vaccine intentions at a population level.

Funding:

Heidelberg Institute of Global Health.

Clinical trial number:

German Clinical Trials Registry (#DRKS00025551).

Article activity feed

  1. Version published to 10.7554/elife.78765 on eLife
  2. eLife

    Evaluation Summary:

    This randomized clinical trial is based on 8,998 participants from the U.S. and the U.K. to examine the association between risk-framing nudges and the willingness to get a Covid vaccine. This manuscript would be of interest to behavioral scientists, particularly behavioral economists. Findings from this work reveal that (1) nudging can substantially increase the likelihood of Covid vaccination; (2) using different nudging frames matters and may produce different results.

    (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)

  3. eLife

    Reviewer #1 (Public Review):

    In this online randomized clinical trial, Sudharsanan et al. used the nudge design/approach to examine the association between framing the risk of the Covid vaccine and the willingness of the participants in getting the vaccine. This is a timely and important study.

    The results indicate that adding a descriptive risk label by the numerical side effect and providing a comparison to mortality due to motor vehicle accidents increased willingness to get the Covid vaccine by 3% and 2.4%, respectively, and independently.

    The study is designed properly, and the manuscript is well written. The findings are important from a policy perspective. Using nudges is an easy and inexpensive way to pursue people toward better decision makings in public health.

    Authors should explain in more detail the methods used to minimize bias. Second, probably the same nudge does not produce homogenous results among different population cohorts. One thing that can strengthen future work is to conduct cluster analysis to examine different nudging mechanisms among different subpopulations.

  4. eLife

    Reviewer #2 (Public Review):

    With participants recruited from the United States and the United Kingdom, Sudharsanan et al. conducted an online randomized controlled trial, which examined three framing strategies of the side effects of a hypothetical COVID-19 vaccine: adding a qualitative risk label next to the numerical risk, adding a comparison group (along with which comparison group is most effective), and for those with comparison groups, framing the comparison in relative terms. Two outcomes were considered in the study: the self-reported willingness to take the vaccine and the perceived safety of the vaccine. Analysis showed that adding a qualitative label and a comparison to motor-vehicle mortality significantly increased the propensity for vaccination, whereas adding a comparison to COVID-19 mortality or framing the comparison in relative terms did not have a significant effect on the willingness of vaccination. These findings add useful evidence to the literature on the behavioral incentives of vaccination uptake.

    The study is well designed and implemented, with the data being carefully collected and analyzed. However, as indicated by the authors, some evidence is nonsignificant or counterintuitive, suggesting a retrospective need to increase the sample size for more convincing and granular results.

    Self-reported willingness to get vaccinated somehow depends upon the regional situation of the pandemic, which is partially reflected by the incidence and mortality among the local population. This factor of potential importance was not accounted for in the study, especially given that participants are recruited from two different countries with different governmental mandates.

  5. eLife

    Reviewer #3 (Public Review):

    The authors were trying to examine if different framing strategies and types of presentation affect an individual's willingness to take vaccines. The paper has several strengths that should be noted. First, they have used a large randomized control trial composed of 8988 participants of adults ages 18 and older conducted in the United States and the United Kingdom. They have found a significant increase in vaccine willingness (about 3%) when a low-risk descriptive risk label is attached to numerical side effects, parallelly when a comparison group is added vaccine willingness also increases by 2.4%. They found these effects to be additive and increase further when combined together (to about 6.1%). Furthermore, they analyzed whether framing strategies varied with respect to age, sex, and country and they found no significant differences. The authors have addressed their aims quite competently and the results also point out that framing strategies are linked to vaccine hesitancy. Overall, this paper does not have too many weaknesses. One area of concern was the loss of 3000 participants for their study which would have been really great for a secondary sub-analysis. Although in the limitation the authors mentioned that the racial composition of the participants varied from the national estimates, it should also be noted that the age composition of participants was also a lot younger than the general population. To sum it up, the authors did a fantastic job of incorporating a novel idea that can be repeated in other countries as well.

  6. Version published to 10.1101/2021.10.12.21264877v2 on medRxiv
  7. ScreenIT

    SciScore for 10.1101/2021.10.12.21264877: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

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  8. Version published to 10.1101/2021.10.12.21264877v1 on medRxiv