Barriers and facilitators of participation in syphilis vaccine trials: a qualitative analysis to inform trial design and community engagement in the United States

Amidst resurging syphilis infection rates, increasing efforts are being made towards development of a syphilis vaccine. This study aims to identify barriers and facilitators of syphilis vaccine trial participation among priority groups for early phase studies. We conducted interviews with English-speaking individuals ≥18 years old recruited from an infectious disease clinic, a sexually transmitted infection (STI) testing site, an online research bulletin board, and HIV community advisory boards in North Carolina from April 2021-June 2022. Eligibility criteria included STI diagnosis within 12 months, people living with HIV (PLWH), men who have sex with men, or persons engaged in transactional sex. The interview guide examined views on syphilis vaccines, trial participation, and community engagement. Interviews were transcribed verbatim, coded, and analysed for emergent themes using a social ecological model. Thirty individuals were interviewed, including eight (27%) women, 13 (43%) Black/African American individuals, and 19 (63%) PLWH. While 19 (63%) interviewees were interested in syphilis vaccine trial participation, 10 (33%) noted participation would depend on trial parameters; one person expressed no interest. Trial participation barriers included physical risks, time commitments, and concerns related to mistrust and mistreatment. Facilitators included advancing science, syphilis prevention, and trusting the researchers. Interviewees emphasized the importance of community involvement to inform vaccine trials, particularly amidst the lingering shadow of the Tuskegee Syphilis Study. While priority groups thus expressed interest in syphilis vaccine trial participation, tailored community engagement will be essential prior to clinical trials. Additional mixed methods research is urgently needed.