Addressing the HIV & STI Syndemic in Prevention Research


HIV illustration

Sexually transmitted infections (STIs) continue to impact global populations, with transmission rates increasing among those vulnerable to HIV acquisition and those living with HIV. Historically, research has focused on STI and HIV prevention separately. Today, experts say this siloed model no longer makes sense, arguing that because HIV and STIs have a syndemic relationship, our approach to preventing them should harness the same synergy.

Globally, more than 1 million sexually transmitted infections (STIs) are acquired daily. While most infections are initially asymptomatic, chlamydia, gonorrhea, syphilis, and trichomoniasis account for 374 million infections each year. Some can lead to long-term health complications if left untreated. Additionally, bacterial STIs and Herpes Simplex Virus 2 (HSV-2) can significantly increase the risk of HIV acquisition.

Dr. Connie Celum, professor of global health and medicine at the University of Washington, says that STIs increase the risk of poor reproductive health outcomes, including congenital syphilis, infertility, ectopic pregnancies, and chronic pelvic pain associated with chlamydial and gonococcal infection. While extensive research has shown the devastating effect of untreated STIs, research into STI prevention has not been as robust as other diseases.

Dr. Connie Celum
Dr. Connie Celum, professor of global health and medicine at the University of Washington.

“We have invested less in evaluating interventions to prevent STIs than in HIV prevention,” said Dr. Celum. “STIs should be part of combination HIV prevention and integrated services for populations we are reaching for HIV prevention research.”

Dr. Meredith Clement, assistant professor of clinical medicine at Louisiana State University and safety physician for the HPTN 083 Clinical Management Committee, agrees that STIs cannot be overlooked in HIV prevention research.

“We’ve learned STIs increase HIV shedding in the genital tract, enhancing transmission, and that they can lead to immune changes, mucosal disruption, and affect the genital microenvironment, leading to increased susceptibility. In turn, HIV can prolong or augment the transmissibility of STIs.”

Dr. Meredith Clement
Dr. Meredith Clement, assistant professor of clinical medicine at Louisiana State University & safety physician for the HPTN 083 Clinical Management Committee.

She notes that this “epidemiological synergy,” discussed in works published by Judy Wasserheit in 1992, shows that the two epidemics feed off one another and that subsequent research has focused on addressing this relationship. “We need to prevent new cases of STIs, and we need to prevent new cases of HIV, and if we truly care about sexual health and wellness, our research should be aimed at both of those goals,” said Dr. Clement.

Curbing these epidemics requires understanding this relationship and the circumstances in which they occur. Dr. Matt Gravett, an infectious disease specialist focused on LGBTQ health and assistant professor of medicine at the University of Alabama at Birmingham, says that while collecting data on STI acquisition in HIV prevention research is important, it doesn’t tell the whole story.

“STIs and HIV are not infections due only to sexual behaviors; they’re also a consequence of sociosexual networks. Understanding that it is social determinants of health and inequitable access to appropriate and affirming sexual healthcare among these sociosexual networks this is impacting the STI and HIV syndemic, is critical to successfully curbing either epidemic.”

Dr. Matt Gravett
Dr. Ronnie "Matt" Gravett, assistant professor of medicine at the University of Alabama Birmingham.

When clinical researchers look to include STI prevention in study design, Gravett says it is essential to meet participants where they are.

“Participants are having sex. Sex is part of the human condition. So, our work should be affirming and inclusive of all persons who are sexually active, regardless of their identity. Beyond that, we should prioritize equity when thinking about implementation strategies. We know structural barriers exist to accessing pre-exposure prophylaxis (PrEP) and other sexual health services, including STI testing and treatment, so if we are mindful of navigating those barriers in the early phases of development, then our product has a better chance of making an impact,” said Dr. Gravett.

But while these epidemics and challenges to curb them continue, researchers are optimistic about upcoming developments and strategies to combat them.

Recently studied DoxyPEP, a method of post-exposure prophylaxis for bacterial STIs, opens the possibility of reducing STI risk among men who have sex with men and transgender women on an event-driven basis. Dr. Celum says this option’s positive impact on intimacy and sex gives people agency and less fear of STI acquisition and transmission.

Additionally, a recent study found that meningitis B vaccines, such as GlaxoSmithKline’s Bexsero, can provide some protection against gonorrhea. More research into its effectiveness against gonorrhea is ongoing. 

“There’s so much in the pipeline – rapid diagnostics for STIs, longer-acting formulations for PrEP, and data emerging all the time about new strategies for treatment and prevention,” Dr. Clement said. “We need to identify effective and safe tools to help reduce the risk of STIs and HIV, and then implement them in accessible and acceptable ways.”

New prevention strategies in development give clinical researchers, community advocates, and healthcare professionals hope for providing individuals options in making choices to support their sexual health. In addition, an informed and renewed, synergized approach signals an optimistic future without the burden of STIs and HIV.

“We are now in the era of biomedical prevention and biomedical prevention options. We can offer prevention strategies that can be better tailored to meet the desires of our patients, clients, and participants.  We are saying, ‘here are some proven tools to empower your sexual health,’ but our work can’t stop there. We must get these tools to the people and communities who need them,” Dr. Gravett said.

On a systematic level, organizations, agencies, and pharmaceutical companies play a role in advancing novel STI and HIV prevention research to address the syndemic. According to Dr. Clement, these entities can use their influence to combat stigma, a common underlying challenge for STIs and HIV. Additionally, she says organizational influence should be leveraged to increase capacity sharing and optimize delivery methods.

“The healthcare workforce is having a supply chain crisis with clinics everywhere short-staffed. While we want to be rolling out innovative programs such as new delivery models for injectable treatment or long-acting PrEP, these are time-and-effort-consuming and often not feasible. Agencies and organizations can help with education and training, peer engagement, and building community partnerships to ease some of that burden,” Dr. Clement said.

Dr. Gravett adds that an effort to streamline the approach and implement wrap-around services will support an effective outcome saying, “We know structural barriers and competing priorities may prevent access to care, so if we can bundle or streamline these, then we have a better chance of being effective for the community.”

Echoing his remarks, Dr. Clement said, “We can’t overestimate the value of community engagement in this work. Community partners I’ve collaborated with in recent years will tell me again and again, ‘it’s about meeting the people where they are.’ Understanding the perspective of our patients and participants, getting out of the ivory research tower and into the neighborhoods, making those connections, and building those relationships – that’s how we will see real change in the coming years.”