During the first full day of research presentations at the 2023 Conference on Retroviruses and Opportunistic Infections (CROI), HIV.gov spoke with Dr. Carl Dieffenbach, Director of the Division of AIDS at NIH’s National Institute of Allergy and Infectious Diseases (NIAID), about some initial highlights, including the opening session that featured a lecture by Dr. Anthony Fauci and several studies about the use of doxycycline for post-exposure prophylaxis (Doxy-PEP) for sexually transmitted infections (STIs). Watch our conversation with Dr. Dieffenbach below:

Dr. Fauci Reflects on the History of HIV

The opening session celebrated the 30^th anniversary of this conference, and Dr. Dieffenbach observed that history was a throughline in several of the opening lectures. Dr. Anthony Fauci, who recently stepped down as Director of NIAID, a position he held since 1984, presented a talk titled “CROI: A 30-Year Chronicle of HIV/AIDS Research Progress,” in which he highlighted several “wow” moments from the history of our understanding of and response to HIV and AIDS and recalled how many significant advances were presented at this conference over the years. Dr. Kevin De Cock traced the history of HIV in Africa, and Yvette Raphael of South Africa reflected on the evolution of the response to HIV among women, particularly in sub-Saharan Africa where they are the most affected population, as well as the vital role of activism and community involvement in clinical trials.

Post-Exposure Prophylaxis for STIs

Dr. Dieffenbach also highlighted three new studies that provided additional information about using a preventive dose of the antibiotic doxycycline within 72 hours after condomless sex to prevent bacterial STIs. First, the DoxyVAC study, presented by Dr. Jean-Michel Molina of the University of Paris Cité, assessed two different strategies to reduce the burden of STIs among gay men on HIV PrEP who had a history of an STI in the prior year. The researchers set out to confirm a previous finding on the effectiveness of the Doxy-PEP strategy and assess whether a second (independent) intervention with the meningococcal B vaccine could also have an impact on gonorrhea incidence. The researchers found that Doxy-PEP significantly reduced the incidence of chlamydia and syphilis and had a significant impact on the incidence of gonorrhea and that the meningococcal B vaccine reduced the incidence of gonorrhea by roughly 50% in the participants who received two doses. Dr. Dieffenbach shared that NIAID is also supporting an ongoing large-scale clinical trialExit Disclaimer at three sites in the southeast United States studying whether the meningococcal B vaccine also can protect participants from infection with the bacteria that causes gonorrhea.

Dr. Anne Luetkemeyer of the University of California, San Francisco, presented additional data from the Doxy-PEP study that had previously demonstrated the effectiveness of the intervention among men and transgender women who have sex with men. The data she presented helped answer the question of whether this use of doxycycline might cause antimicrobial resistance in the bacterial STIs it is intended to prevent. Her analysis found there was no marked increase in doxycycline resistance among three key bacteria, including gonorrhea and Staphylococcus aureus, which can cause diseases.

However, as Dr. Dieffenbach discussed, a study from Kenya presented by Dr. Jenell Stewart of the University of Minnesota indicates that Doxy-PEP may not be effective for women. The study of 449 young cisgender women who were using PrEP found that the use of Doxy-PEP following condomless sex did not reduce incident STIs in this population. She noted that the findings raised questions for further exploration, such as whether the ineffectiveness of Doxy-PEP in this study could be due to differing drug concentrations in vaginal/cervical tissue vs rectal tissue, low adherence, or antimicrobial resistance.

About CROI

CROI is an annual scientific meeting that brings together leading researchers and clinical investigators from around the world to present, discuss, and critique the latest studies that can help accelerate global progress in the response to HIV and AIDS and other infectious diseases, including viral hepatitis, COVID-19, and mpox. More than 3,400 HIV and infectious disease researchers from 72 countries are gathered in Seattle and virtually this year for this forum. Among the studies that are being presented are many that were conducted or supported by NIH, CDC, and other federal agencies. Visit the conference websiteExit Disclaimer for more information; abstracts, session webcasts, and e-posters will be published there for public access in 30 days.

More HIV Research Updates to Follow on HIV.gov

HIV.gov is sharing additional video interviews from CROI 2023 with Dr. Dieffenbach as well as with HRSA’s Dr. Laura Cheever and CDC’s Dr. Jono Mermin and Dr. John Brooks. You can find them on our social media channels and re-capped here on the blog. Be sure to watch, comment, and share!