Seasonal influenza causes substantial global harms, and promoting vaccination among healthcare workers (HCW) is a central prevention strategy. The reported studies evaluated whether correcting common influenza myths and explicitly addressing concerns about vaccine adverse reactions influence intentions to be vaccinated. Both experiments were delivered online and included HCW samples and general population comparison samples.
Experiment 1 recruited HCW (n = 514) and a general population sample (n = 401). Participants viewed images designed to debunk common influenza myths. Participants were randomised to materials that either did or did not include an additional image specifically addressing adverse reactions.
The primary outcome was self-reported vaccination intention. The experiment found that myth-busting materials significantly increased vaccination intentions in both HCW and general population samples (reported p < .001 and effect sizes ηp2 > 0.12 for comparisons). However, including the additional image that explicitly addressed adverse reactions did not produce a further increase in intentions beyond the myth-busting content alone.
Experiment 2 focused on messaging about adverse reactions. This study included HCW (n = 535) and a larger general population sample (n = 1200). Participants were randomised to one of four image formats that communicated about adverse reactions.
For HCW, no overall main effect of adverse-reaction messaging on intentions was observed. However, a significant interaction by image format was reported (p = .011, ηp2 = 0.04), indicating heterogeneous effects across the four images. Specifically, one image increased vaccination intentions (p = .029, dz = 0.25), two images produced null effects, and one image produced a marginal backfire effect (p = .052, dz = -0.21), where intentions were slightly reduced.
In the general population arm of Experiment 2, vaccination intentions increased overall after exposure to the adverse-reaction materials (p < .001, dz = 0.15), and no interaction by image format was reported in that sample.
Myth-busting material reliably increased vaccination intentions in Experiment 1 for both HCW and general population (all reported p < .001, all ηp2 > 0.12).
Adding an adverse reactions image to myth-busting materials in Experiment 1 did not add measurable benefit.
In Experiment 2 among HCW, message format moderated effects (interaction p = .011, ηp2 = 0.04): one image significantly increased intentions (p = .029, dz = 0.25), two were neutral, and one marginally reduced intentions (p = .052, dz = -0.21).
In the Experiment 2 general population sample, adverse-reaction messaging increased intentions overall (p < .001, dz = 0.15) without image-format interaction.
These findings indicate that while myth-busting shows a consistent positive effect on stated intentions, messaging that explicitly addresses mild adverse reactions is not uniformly effective and may vary by design and audience.
The authors conclude that myth-busting is an effective approach for increasing influenza vaccination intentions. In contrast, explicitly addressing mild adverse reactions did not reliably raise intentions among HCW and in one tested format had a marginal backfire effect. The pattern of results differed between HCW and the general population in Experiment 2, suggesting audience matters when designing messages about adverse reactions.
For campaigns targeting HCW, the authors recommend testing adverse reaction messaging before broad implementation because message format can alter effects and, in some cases, reduce intentions. The studies support continuing to use myth-debunking materials to increase uptake intentions but caution against assuming adverse-reaction explanations will add benefit without prior evaluation.
The published article lists funding support reported for one author from UK Research and Innovation Economic and Social Research Council. Other authors declared no known competing financial interests or personal relationships that could have influenced the work. The abstract reports the experimental design, samples, and primary outcomes; details beyond the abstract (such as image content, exact randomisation procedures, timing, or demographic breakdowns) were not reported in the provided source text.