Enrollment in DANFLU-2 trial was significantly more likely for those receiving single-page letter versus two-page letters<\/p>\n<\/h3>\n
By Elana Gotkine HealthDay Reporter<\/b>
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TUESDAY, July 8, 2025 (HealthDay News) — Shorter-form messaging seems to be preferable for recruiting participants to enroll in clinical trials, according to a research letter published online June 25 in the Journal of the American Medical Association<\/em>.<\/p>\n Niklas Dyrby Johansen, M.D., Ph.D., from Copenhagen University Hospital in Denmark, and colleagues examined whether varying digital recruitment letter layout and color scheme would impact trial enrollment in a randomized experiment conducted within the context of the DANFLU-2 (A Pragmatic Randomized Trial to Evaluate the Effectiveness of High-Dose Quadrivalent Influenza Vaccine vs Standard-Dose Quadrivalent Influenza Vaccine in Older Adults) trial. Layout and color scheme were varied in a 3×3 factorial design. Invitees were randomly assigned to receive one of three layout variants — a single-page letter, two-page letter, or enhanced two-page letter with additional colored text boxes — and to receive one of three color schemes (dark red, blue, or green). Across all letters, the text content was identical.<\/p>\n A total of 934,049 Danish citizens aged 65 years and older were randomly assigned to receive different letter types; letters were successfully delivered to 99.95 percent. Overall, 160,451 participants were enrolled in DANFLU-2 during the 2023 to 2024 season. The researchers found that enrollment in DANFLU-2 was significantly more likely among participants who received the single-page letter versus the two-page letter and enhanced two-page letter (16.28 percent versus 16.02 and 15.29 percent, respectively). Across the color schemes, no differences were observed. There were no interactions noted between letter layout and color scheme.<\/p>\n “These findings do underline the importance of carefully considering design and style of participant-facing material in clinical trials, including recruitment letters, particularly in decentralized pragmatic trials where broadly distributed, low-touch recruitment strategies are often necessary,” the authors write.<\/p>\n Several authors disclosed ties to pharmaceutical companies, including Sanofi, which funded the DANFLU-2 trial.<\/p>\n Abstract\/Full Text (subscription or payment may be required)<\/a><\/p>\n Editorial (subscription or payment may be required)<\/a><\/p>\n