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During April, STD Awareness provides an opportunity to talk about STIs and encourage individuals to be proactive about their sexual health and promotes regular STI/HIV screening and testing. Although research in sexually transmitted infections (STIs) has evolved rapidly on multiple fronts, a critical remaining challenge is the development of safe and effective vaccines for diseases that pose significant and growing public health burdens. At this time, the only vaccine for an STI is the Human Papillomavirus (HPV) vaccine, a virus that can cause genital warts and is also linked to certain cancers. There are no vaccines to prevent syphilis, gonorrhea or chlamydia.

Visiting scholar Yaw Agyekum Boaitey in the UNC IDEEL Laboratory uses molecular methods to characterize samples from his study in Ghana.

The CDC’s 2020 STD Surveillance Report shows sexually-transmitted diseases (STDs) are on the rise with 2.4 million cases of chlamydia, gonorrhea, and syphilis reported in 2020. In 2019, the NIH’s National Institute of Allergy and Infectious Diseases (NIAID) announced U19 awards to establish Cooperative Research Centers (CRCs) focused on developing vaccines for bacterial STIs. Collaborative multidisciplinary research is underway at several universities, including the UNC Institute for Global Health & Infectious Diseases (IGHID) and UNC School of Medicine.

Syphilis Research

Arlene Sena headshot
Arlene Seña, MD, MPH

Arlene Seña, MD, MPH, professor in infectious diseases, is a co-project director to establish a global clinical researchconsortium for syphilis vaccine development through the IGHID, with sites in Malawi, China, and Colombia.

“We are collecting clinical data and specimens from individuals with syphilis in order to determine which outer membrane proteins on the surface of the bacteria Treponema pallidum are highly antigenic and could be future vaccine candidates,” explained Seña.

“We are also working with UNC Project Malawi and other clinical sites to collect important behavioral and clinical information that could help with vaccine modeling, in order to determine the potential impact of a syphilis vaccine and the key populations that we should focus on when a vaccine becomes available.”

Suzanne Day, PhD MA
Suzanne Day, PhD, MA

Suzanne Day, PhD, MA, assistant professor in infectious diseases, is working on a developmental research project to evaluate syphilis vaccine trial feasibility. Her formative work assesses the stigma associated with syphilis, with qualitative surveys in our infectious disease clinic and other clinics, to determine the barriers and facilitators of participation in syphilis vaccine research.

CDC data show syphilis began doubling in 2012, with the US male to female ratio currently at 4:1, and that men having sex with men have accounted for a majority of all male cases. Data also show a notable increase in the heterosexual syphilis epidemic believed to be due to mixing between sexual networks. Meanwhile, primary syphilis rates among women, although they’re much lower than they are in men, have more than doubled between 2016 and 2020. Finally, congenital syphilis cases, from 2016 to 2020, have increased 254%. Seña points to delays in diagnosis and treatment of syphilis in pregnant women as the cause for the rise in congenital syphilis cases nationwide.

Credit: CDC Website

Genomic Epidemiology

Jonathan Parr, MD

Dr. Seña has also been awarded a grant from the Bill and Melinda Gates Foundation to understand syphilis genomic epidemiology. She is working with other academic institutions and international sites to understand the global distribution of T. pallidum in low- and middle-income countries, and the genetic variability of the bacteria that could inform syphilis vaccine development. Jonathan Parr, MD, MPH, assistant professor in infectious diseases, and his laboratory have been making great progress with genome sequencing of T. pallidum for the Gates project as well as the NIAID CRC grant for syphilis vaccine research.

Gonococcal Research

Gonorrhoea, caused by the pathogen Neisseria gonorrhoeae, is the second most common bacterial sexually transmitted infection (STI). Resistance to many older antibiotics, as well as growing resistance to recommended therapies including cephalosporins and macrolides, has made N. gonorrhoeae a multidrug resistant pathogen.

Joseph Alex Duncan, MD, PhD, professor in infectious diseases, and Marcia Hobbs, PhD, professor of medicine and microbiology and immunology, are leading a NIAID-funded study to test whether  a vaccine already in use to prevent Neisseria meningitidis also provides protection from gonorrhea. The four-component meningococcal B vaccine has been demonstrated in epidemiologic studies to potentially have a moderate protective effect against gonorrhea. The UNC team is enrolling participants to determine the efficacy of vaccination, and evaluating the immunologic responses to gonorrhea after vaccination. Both Dr. Duncan and Hobbs are also co-investigators in the U19 CRC for N. gonorrhoeae vaccine research.

Marcia Hobbs, PhD, and Alex Duncan, MD, PhD

Chlamydia Trachomatis Research

Toni Darville, MD, chief of pediatric infectious diseases, is the lead PI on the NIAID-supported CRC grant for Chlamydia trachomatis vaccine development that aims to decrease the burden of infertility and improve the health of young people.

Toni Darville, MD

Chlamydia trachomatis is the most common sexually transmitted bacterial pathogen in the world. CDC estimates that at least 1.7 million cases of chlamydia were diagnosed in the United States in 2017, 45 percent of which were in women aged 15 to 24 years. Most infections are asymptomatic, but untreated chlamydia infections in women can lead to pelvic inflammatory disease or infertility and have been linked to ovarian cancer.

The U19 Sexually Transmitted Infections Cooperative Research Center (STI CRC), “University of North Carolina – Chlamydia Vaccine Initiative (UNC-CVI)” brings together a synergistic multidisciplinary group of project leaders/principal investigators (PI) with clinical and basic research expertise in STI research and a history of effective collaboration, to support a vaccine development pipeline comprising vaccine antigen assessment, vaccine testing in animal models, and identification of human correlates of efficacy.

“The issue with gonorrhea and chlamydia is that the highest number of cases nationwide are among young people, including adolescents and young adults, who are sexually active,” said Seña. “With gonorrhea, we have the additional threat of antimicrobial resistance, so we need new therapeutics as well as vaccines for prevention.

“There’s also the connection with HIV. We know that all STIs increase the risk of acquisition and transmission of HIV. In particular, syphilis is also affecting people living with HIV, and can lead to long term consequences like neurosyphilis, especially in this population.”

UNC physicians encourage individuals to be proactive about their sexual health and promotes regular STI/HIV screening and testing. “We encourage people to have good sexual practices that include condom use and periodic screening. Having vaccines against STIs will be important for future prevention efforts,” Seña said.

Enroll in a Trial

Individuals who want to enroll in a trial for STI vaccine development can visit Research for Me or contact

About the Institute for Global Health & Infectious Diseases

Established in 2007, the Institute for Global Health & Infectious Diseases (IGHID) brings transformative solutions to the most important global health issues of our time, through research, training and service. The IGHID has saved millions of lives and shaped policy worldwide through cutting-edge research, especially in the areas of HIV, Malaria and now COVID, where UNC is the most cited university in the nation for coronavirus research. Working in over 50 countries around the globe, the IGHID provides a unique pan-university framework for collaboration and facilitating global health science and practice. It is this framework that continues to catalyze a global health community committed to improving health worldwide while building the capacity of thousands of scientists and health professionals globally.