OBJECTIVES: To make informed decisions, the general population should have access to accessible and understandable health recommendations. To compare understanding, accessibility, usability, satisfaction, intention to implement, and preference of adults provided with a digital "Plain Language Recommendation" (PLR) format vs. the original "Standard Language Version" (SLV). STUDY DESIGN AND SETTING: An allocation-concealed, blinded, controlled superiority trial and a qualitative study to understand participant preferences. An international on-line survey. 488 adults with some English proficiency. 67.8% of participants identified as female, 62.3% were from the Americas, 70.1% identified as white, 32.2% had a bachelor's degree as their highest completed education, and 42% said they were very comfortable reading health information. In collaboration with patient partners, advisors, and the Cochrane Consumer Network, we developed a plain language format of guideline recommendations (PLRs) to compare their effectiveness vs. the original standard language versions (SLVs) as published in the source guideline. We selected two recommendations about COVID-19 vaccine, similar in their content, to compare our versions, one from the World Health Organization (WHO) and one from Centers for Disease Control and Prevention (CDC). The primary outcome was understanding, measured as the proportion of correct responses to seven comprehension questions. Secondary outcomes were accessibility, usability, satisfaction, preference, and intended behavior, measured on a 1-7 scale. RESULTS: Participants randomized to the PLR group had a higher proportion of correct responses to the understanding questions for the WHO recommendation (mean difference [MD] of 19.8%, 95% confidence interval [CI] 14.7-24.9%; P < 0.001) but this difference was smaller and not statistically significant for the CDC recommendation (MD of 3.9%, 95% CI -0.7% to 8.3%; P = 0.096). However, regardless of the recommendation, participants found the PLRs more accessible, (MD of 1.2 on the seven-point scale, 95% CI 0.9-1.4%; P < 0.001) and more satisfying (MD of 1.2, 95% CI 0.9-1.4%; P < 0.001). They were also more likely to follow the recommendation if they had not already followed it (MD of 1.2, 95% CI 0.7-1.8%; P < 0.001) and share it with other people they know (MD of 1.9, 95% CI 0.5-1.2%; P < 0.001). There was no significant difference in the preference between the two formats (MD of -0.3, 95% CI -0.5% to 0.03%; P = 0.078). The qualitative interviews supported and contextualized these findings. CONCLUSION: Health information provided in a PLR format improved understanding, accessibility, usability, and satisfaction and thereby has the potential to shape public decision-making behavior.

Centre for Immunization Readiness Public Health Agency of Canada Ottawa Ontario K1A 0K9 Canada

Child Health Evaluative Sciences The Hospital for Sick Children Research Institute Toronto Ontario M5G 0A4 Canada

Child Health Evaluative Sciences The Hospital for Sick Children Research Institute Toronto Ontario M5G 0A4 Canada; Department of Psychiatry University of Toronto Toronto Ontario M5T 1R8 Canada

Child Health Evaluative Sciences The Hospital for Sick Children Research Institute Toronto Ontario M5G 0A4 Canada; Institute of Health Policy Management and Evaluation University of Toronto Toronto Ontario M5T 3M6 Canada; Division of Neonatology The Hospital for Sick Children University of Toronto Toronto Ontario M5G 1X8 Canada

Cochrane South Africa South African Medical Research Council Capetown South Africa; Division of Epidemiology and Biostatistics Department of Global Health Faculty of Medicine and Health Sciences Stellenbosch University Stellenbosch South Africa

Czech National Centre for Evidence Based Healthcare and Knowledge Translation Institute of Biostatistics and Analyses Faculty of Medicine Masaryk University 625 00 Brno Czech Republic; Institute of Health Information and Statistics of the Czech Republic Prague Czech Republic

Department of Biology Faculty of Science University of Ottawa Ottawa Ontario K1N 6N5 Canada; Schulich School of Medicine and Dentistry Western University London Ontario N6A 5C1 Canada; Department of Health Research Methods Evidence and Impact Michael G DeGroote Cochrane Canada and GRADE Centres McMaster University 1280 Main St W Hamilton Ontario L8S 4K1 Canada

Department of Health Research Methods Evidence and Impact Michael G DeGroote Cochrane Canada and GRADE Centres McMaster University 1280 Main St W Hamilton Ontario L8S 4K1 Canada

Department of Health Research Methods Evidence and Impact Michael G DeGroote Cochrane Canada and GRADE Centres McMaster University 1280 Main St W Hamilton Ontario L8S 4K1 Canada; Department of Anesthesia McMaster University Hamilton Ontario Canada; Department of Pediatrics McMaster University Hamilton Ontario Canada; Biostatistics Unit Father Sean O'Sullivan Research Centre St Joseph's Healthcare Hamilton Ontario Canada; Centre for Development of Best Practices in Health Yaoundé Central Hospital Yaoundé Cameroon; Division of Epidemiology and Biostatistics Department of Global Health Stellenbosch University Cape Town South Africa

Department of Health Research Methods Evidence and Impact Michael G DeGroote Cochrane Canada and GRADE Centres McMaster University 1280 Main St W Hamilton Ontario L8S 4K1 Canada; Department of Biomedical Sciences Humanitas University Milan Italy

Department of Health Research Methods Evidence and Impact Michael G DeGroote Cochrane Canada and GRADE Centres McMaster University 1280 Main St W Hamilton Ontario L8S 4K1 Canada; Department of Internal Medicine American University of Beirut Beirut Lebanon

Department of Health Sciences Faculty of Medicine Masaryk University Brno Czech Republic

Department of Pediatrics Faculty of Medicine and Dentistry Alberta Research Center for Health Evidence University of Alberta Edmonton Alberta Canada

Department of Pediatrics Faculty of Medicine and Dentistry Alberta Research Center for Health Evidence University of Alberta Edmonton Alberta Canada; Cochrane Child Health University of Alberta Edmonton Alberta Canada

Faculty of Nursing University of Alberta Edmonton Alberta Canada

Five02 Labs Inc Toronto Ontario Canada

National Evidence and Quality Platform St Elizabeth University of Public Health and Social Science Research Dept Nam 1 Maja 1 81000 Bratislava Slovak Republic; Experts Consortium for COVID 19 Advisor to Government of Slovak Republic Bratislava Slovak Republic; WHO Executive Board Geneva Switzerland

National Institute for Health Technology Assessment Federal University of Rio Grande do Sul Porto Alegre Brazil

Postgraduate Institute of Medical Education and Research Chandigarh India

Schulich School of Medicine and Dentistry Western University London Ontario N6A 5C1 Canada; Department of Family Medicine Western University London Ontario Canada

References provided by Crossref.org