Publication date: Dec 01, 2025

During the COVID-19 pandemic, recruitment for vaccine clinical trials was conducted quickly and in large numbers. This study was conducted to analyze participant sentiments that were unique in such a situation. A cross-sectional self-administered electronic survey was completed between May and July 2022 by 163 participants in Phase 2/3 COVID-19 vaccine clinical trials at the Center for Immunization Research in Baltimore, Maryland. Descriptive statistics of participant characteristics, their study experiences, and retrospective perceived risks before and after the study were analyzed. Approximately half of participants were female (52. 1%), greater than 55 years old (50. 9%), and had a masters or doctoral level degree (58. 9%). The majority were White or Caucasian (71. 2%) and not of Hispanic, Latino, or Spanish origin (92. 6%). 44. 2% earned more than $99,999 each year. Most participants joined to obtain protection against COVID-19 (42. 3%) or to help others/contribute to science (38. 7%). Only 4. 3% joined for the money. There was a significant reduction in perceived risk of the study once participants had completed it; 81 (49. 7%) participants considered the study less risky at the end compared to before joining, whereas only 2 (1. 2%) considered it more risky. Participants in COVID-19 vaccine trials tend to be whiter, more educated, and wealthier than the general population, and perceived the trials riskier prior to participating than once they had completed. While limited by low response rate and recall error, this study suggests that in future emergency situations, messaging should be prioritized to improve understanding of trials and vaccines.

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