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OBJECTIVES: Recruitment remains a major challenge in clinical research, particularly among young populations. This study evaluated the effectiveness of a paid social media influencer campaign as a recruitment strategy for the MeMaF study (Menstrual Health and Hybrid Care Model for All Young Females), which targets young women with severe menstrual pain in Germany. STUDY DESIGN AND SETTING: This mixed methods study was nested within the MeMaF single-arm trial. Recruitment data were collected via the study app, and three recruitment periods were defined retrospectively: (1) basic recruitment period (March 8, 2024-January 8, 2025), (2) social media influencer campaign (January 9-31, 2025), and (3) postcampaign period (February 1-28, 2025). Quantitative analyses included descriptive statistics of daily enrollments, app downloads, and download-to-enrollment ratios across the three recruitment periods. Qualitative data consisted of anonymized social media comments from Instagram and TikTok related to the influencer postings. A thematic content analysis was conducted using MAXQDA, supported by large language models integrated into the software. RESULTS: Over the entire recruitment period, 3496 participants were enrolled, thereby meeting the recruitment goal. The mean daily enrollment rate during the social media influencer campaign (45.5 participants/day) was six times higher than during the basic recruitment period (6.8 participants/day) and remained elevated in the postcampaign period (13.4 participants/day). Posts from six female influencers accumulated 2.8 million views and 114,600 likes on Instagram, and 865,000 views and 100,000 likes on TikTok. Qualitative analysis of 501 comments revealed strong audience engagement, including discussion of the study's inclusion criteria, often expressing criticism of eligibility restrictions alongside appreciation for the study initiative. Comment sections also evolved into a space for sharing personal experiences with menstrual pain and healthcare access. CONCLUSION: A paid influencer campaign can substantially enhance study recruitment among young populations. Collaboration with influencers represents a feasible and effective strategy to broaden reach, strengthen engagement, and complement traditional recruitment methods. Future studies should evaluate cost-effectiveness and transferability to other populations and platforms. PLAIN LANGUAGE SUMMARY: Recruiting participants for clinical studies can be difficult, especially among young people. This study examined whether social media influencers, popular online personalities on platforms such as Instagram and TikTok, can help improve recruitment. We used a paid influencer campaign to promote a study on menstrual health among young women in Germany. Six influencers shared information about the study with their followers. We compared how many people joined the study before, during, and after the campaign. During the influencer campaign, the number of people enrolling in the study increased six-fold compared to the period before the campaign. The posts also received high engagement, including many views, likes, and comments. In the comments, users discussed the study, shared personal experiences, and sometimes expressed frustration about who was eligible to participate. These findings suggest that working with social media influencers can be an effective way to reach young people and increase participation in clinical studies.
Lysk et al. (Wed,) studied this question.