The impact of side effect framing on COVID-19 booster vaccine intentions in an Australian sample

Objective: To evaluate the effect of presenting positively attribute-framed side effect information on COVID-19 booster vaccine intention relative to standard negatively-framed wording and a no-intervention control.Design and participants: A representative sample of Australian adults (N = 1204) were randomised to one of six conditions within a factorial design: Framing (Positive; Negative; Control) x Vaccine (Familiar (Pfizer); Unfamiliar (Moderna)).Intervention: Negative Framing involved presenting the likelihood of experiencing side effects (e.g., heart inflammation is very rare, 1 in every 80,000 will be affected), whereas Positive Framing involved present-ing the same information but as the likelihood of not experiencing side effects (e.g., 79,999 in every 80,000 will not be affected).Primary outcome: Booster vaccine intention measured pre-and post-intervention.Results: Participants were more familiar with the Pfizer vaccine (t(1203) = 28.63, p <.001, Cohen's dz = 0.83). Positive Framing (M = 75.7, SE = 0.9, 95% CI = [73.9, 77.4]) increased vaccine intention relative to Negative Framing (M = 70.7, SE = 0.9, 95% CI = [68.9, 72.4]) overall (F(1, 1192) = 4.68, p =.031, gp2 = 0.004). Framing interacted with Vaccine and Baseline Intention (F(2, 1192) = 6.18, p =.002, gp2 = 0.01). Positive Framing was superior, or at least equal, to Negative Framing and Control at increasing Booster Intention, irrespective of participants' pre-intervention level of intent and vaccine type. Side effect worry and perceived severity mediated the effect of Positive vs. Negative Framing across vaccines.Conclusion: Positive framing of side effect information appears superior for increasing vaccine intent rel-ative to the standard negative wording currently used. Pre-registration: See: aspredicted.org/LDX_2ZL.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).

Automated summary

The study evaluated the effect of positively attribute-framed side effect information on COVID-19 booster vaccine intention. The results showed that positive framing increased vaccine intention and was not affected by pre-intervention level of intent and vaccine type.