Evidence Record

Evidence summary

In a blinded randomized international online trial with 488 adults, plain-language recommendations improved comprehension substantially for one health recommendation but not significantly for another; accessibility and satisfaction improved for both.

Exact claim supported or contradicted

Supports the claim that plain language can improve outcomes but is not uniformly sufficient, and that comprehension and preference are distinct.

Source provenance

Peer-reviewed controlled superiority trial with allocation concealment, blinded assessment framing, registered outcome measures, and a linked qualitative study. PubMed record and abstract inspected.

Relevant excerpt or data

WHO item comprehension: mean difference 19.8 percentage points (95% CI 14.7–24.9). CDC item: 3.9 points (95% CI -0.7–8.3). Accessibility and satisfaction favored the plain-language versions.

Interpretation

The baseline text and information structure moderate intervention effects. A test must compare outcomes per task and must not infer comprehension from satisfaction.

Limitations

Online English-proficient sample was demographically uneven; only two COVID-19 vaccine recommendations were compared.

Counterevidence

The large WHO-item effect supports plain language as a promising component when the baseline is difficult.

Reproduction or verification notes

PubMed PMID 38008266; DOI above.