A multimethods randomized trial found that plain language versions improved parents' understanding of health...

To assess the effectiveness of plain language compared with standard language versions of COVID-19 recommendations specific to child health.

Pragmatic, allocation-concealed, blinded, superiority randomized controlled trial with nested qualitative component. Trial was conducted online, internationally. Parents or legal guardians (≥18 years) of a child (<18 years) were eligible. Participants were randomized to receive a plain language recommendation (PLR) or standard (SLV) verison of a COVID-19 recommendation specific to child health. Primary outcome was understanding. Secondary outcomes included: preference, accessibility, usability, satisfaction, and intended behavior. Interviews explored perceptions and preferences for each format.

Between July and August 2022, 295 parents were randomized; 241 (81.7%) completed the study (intervention n = 121, control n = 120). Mean understanding scores were significantly different between groups (PLR 3.96 [standard deviation (SD) 2.02], SLV 3.33 [SD 1.88], P = 0.014). Overall participants preferred the PLR version: mean rating 5.05/7.00 (95% CI 4.81, 5.29). Interviews (n = 12 parents) highlighted their preference for the PLR and provided insight on elements to enhance future knowledge mobilization of health recommendations.

Compared to SLVs, parents preferred PLRs and better understood the recommendation. Guideline developers should strive to use plain language to increase understanding, uptake, and implementation of evidence by the public.