“The morning-after pill.” How one country for the first time in 15 years stopped the rise in syphilis and chlamydia cases among gay and bisexual men

For the first time in the past 15 years, the epidemiological situation for sexually transmitted infections (STIs) has begun to improve. The study, presented at the 26th International AIDS Conference (AIDS 2026) in Rio de Janeiro, showed that the widespread adoption of DoxyPEP in Australia led to a sharp decline in syphilis and chlamydia rates among gay and bisexual men.

The Australian study was the first to show how this practice works not in controlled experimental conditions, but at the national level.

What is DoxyPEP?

DoxyPEP (Doxycycline, Doxycycline Post-Exposure Prophylaxis) — a strategy for preventing bacterial STIs that involves taking a single dose of the antibiotic doxycycline (200 mg) within 72 hours after sexual contact.

The effectiveness of this method was proven in clinical trials in San Francisco and Seattle. The results were impressive:

• For people without HIV who take PrEP: the reduction in the risk of chlamydia infection was 88%, syphilis — 87%.
• For people living with HIV: the reduction in the risk of chlamydia was 74%, syphilis — 77%.

• Mechanism: Doxycycline is a broad-spectrum antibiotic from the tetracycline class. When taken within 72 hours (and preferably as soon as possible) after unprotected sex, high concentrations of the drug in the blood and body tissues suppress bacteria Treponema pallidum (the cause of syphilis) and Chlamydia trachomatis (the cause of chlamydia) before they manage to attach and cause a full-blown infection.
• Rules: In international practice, DoxyPEP means taking 200 mg of doxycycline once within three days after sexual contact that could lead to infection.

What happened?

In recent years, global public health has been sounding the alarm: STI rates have been steadily rising. However, data from Australia offer a rare reason for optimism. Researchers at the Burnet Institute in Melbourne analyzed records from a national sexual health clinic network covering tens of thousands of patients and found a direct link between the introduction of official recommendations for DoxyPEP use and a decrease in the number of diagnoses.

According to Dr. Michael Traeger, who presented the study results, this is the first time in a decade and a half that a sustained decline in rates has been achieved — if you don’t count the COVID-19 pandemic period, when social contact was artificially restricted.

Results in Australia: ACCESS data

Researchers at the Burnet Institute in Melbourne analyzed data from the national ACCESS clinic network, which covers 29 medical centers. Comparing the periods "before" (January 2022 — April 2023) and "after" (October 2023 — October 2025) the introduction of national recommendations showed:

• Syphilis: Disease incidence decreased by 55% compared with what would have been expected if the previous trend had continued. According to the researchers' estimates, about 2,973 cases of the disease were prevented.
• Chlamydia: The number of diagnoses fell by 36%, which is equivalent to about 7,604 prevented cases.

Dr. Traeger noted that syphilis began to decline earlier than chlamydia, which may indicate a "treatment as prevention" effect: taking the drug helps suppress the infection in a person more quickly, limiting its transmission to partners.

Is there a catch?

Not everything is so ideal. Scientists unfortunately note that gonorrhea DoxyPEP is much less effective. In an Australian study, gonorrhea incidence even showed a slight (statistically insignificant) increase.

The main problem lies in resistance: many strains of gonococci have already developed resistance to antibiotics, and doxycycline is losing effectiveness against them. Experts also warn that uncontrolled use of antibiotics can contribute to the growth of antibiotic resistance in the population as a whole, so the method requires medical supervision.

What's next?

Despite the successes, doctors emphasize: DoxyPEP is not a “magic pill” that replaces all other prevention methods, including barrier contraception and vaccination.

To date, Australia has become one of the leaders in implementing this strategy, and the country’s success clearly shows that modern prevention methods can turn the tide even on the most severe epidemiological trends. Nevertheless, the scientific community continues to search for more effective solutions to fight gonorrhea, which remains the main challenge in the world of “post-COVID” sexual health.

The Australian experience shows that DoxyPEP is a powerful public health tool. Despite concerns about gonorrhea and the need for further monitoring, including the issue of antibiotic resistance, this is the first example in many years of a successful reversal of the epidemiological trend for STIs, which has confirmed “clinical” expectations at the national level.

Important: the material is based on study results presented at the AIDS 2026 conference. Using antibiotics without consulting a doctor is not allowed. To choose the optimal prevention strategy, consult a sexual health specialist.