Syphilis Vaccines

Authored by
Staff
Last reviewed
February 11, 2024
Content Overview
Syphilis vaccines continue to be developed, but no vaccine candidate has been US FDA approved.

Syphilis Vaccines 2024

As of February 11, 2024, the U.S. Food and Drug Administration (FDA), the United Kingdom's NHS, and the European Medicines Agency (EMA) have not approved a syphilis prevention vaccine. The U.S. National Institute of Allergy and Infectious Diseases (NIAID) funds Sexually Transmitted Infection (STI) cooperative vaccine research centers (CRCs) to advance the development of syphilis vaccine concepts. In their pursuit of a syphilis vaccine, the CRCs are investigating the structure of proteins on the outer membrane (layer) of T. pallidum bacteria as potential vaccine targets and developing the tri-antigen vaccine featured at the STI & HIV World Congress.

The continued prevalence and severity of Syphilis and Congenital Syphilis (CS) in women and infants highlights the need for an effective preventive vaccine, says the World Health Organization (WHO). The U.S. Centers for Disease Control and Prevention (CDC) reported over 3,700 CS cases in 2022, a one-year increase of 30%. On February 8, 2024, new CDC syphilis testing recommendations were issued supporting a diagnosis of syphilis, including serologic testing and methods for the identification of the causative agent Treponema pallidum.

Syphilis Vaccine Candidates

April 6, 2023 - Frontiers in Immunology published Syphilis vaccine: challenges, controversies, and opportunities. "In this review, researchers describe what is known about the Treponema pallidum subspecie pallidum (TPA) immune response and the main mechanisms this pathogen uses to evade it. They also emphasize the importance of integrating this knowledge, in conjunction with the characterization of outer membrane proteins, to expedite the development of a syphilis vaccine that can protect against TPA infection.

March 1, 2023 - The U.S. NIAID seeks applicants who can develop advanced vaccines for STI pathogens with limited product development pipeline candidates.

December 12, 2022 - A study showed that immunization with a TprC/TprK/Tp0751 tri-antigen cocktail protects animals from progressive syphilis lesions and substantially inhibits the dissemination of the infection.

July 28, 2022 - The journal Frontiers in Immunology published: Notes on syphilis vaccine development. Herein, we overview current technologies and approaches employed in syphilis vaccinology and possible directions to develop a vaccine that could be pivotal to future syphilis control and elimination initiatives.

November 25, 2021 - Original Research: Two Potential Syphilis Vaccine Candidates Inhibit Dissemination of Treponema Pallidum. These results provide novel and critical information for understanding the pathogenic mechanisms of spirochetes and the development of spirochete-specific subunit vaccines. Furthermore, these findings indicate that Tp0136 and Tp0663 are promising syphilis vaccine candidates.

National Syphilis and Congenital Syphilis Syndemic Federal Task Force

Announced in 2023, the National Syphilis and Congenital Syphilis Syndemic Federal Task Force is utilizing HHS agencies, its expertise, and its stakeholder network to respond to the U.S. syphilis and congenital syphilis epidemic. 

Syphilis Treatments

The U.S. HHS Healthy People 2030 goal focuses on reducing women with syphilis who can also pass the virus to their children during pregnancy. The CDC's Vital Signs report published on November 7, 2023, confirmed about 88% of CS cases could be prevented by timely testing and adequate treatment during pregnancy. The Syphilis in Pregnancy Study (SIPS) is monitoring the outcomes of pregnant people diagnosed with and treated for syphilis, as well as the health outcomes of their infants. 

A new study presented at IDWeek 2023 found a single dose of benzathine penicillin G (BPG) is effective against early syphilis regardless of HIV status. The U.S. CDC recommends a single injection of BPG, indicating it can cure early syphilis and primary, secondary, and latent infections. However, three BPG doses at 1-week intervals for more severe infections, including late latent syphilis and latent syphilis of unknown duration. Bicillin L-A® is the first-line recommended treatment for syphilis and the only recommended treatment option for some patients. Benzathine penicillin G is the WHO and CDC's only recommended treatment for syphilis during a woman's pregnancy.

On January 10, 2024, the FDA's website confirmed the agency would temporarily allow the importation of Laboratoires Delbert's injectable benzathine penicillin G, Extencilline, Powder, and diluent for reconstitution for injection, 1,200,000 units and 2,400,000 units with Foreign, non-U.S. Labeling to Address Supply Shortage.

The University of California, San Francisco, led a phase 4 clinical trial that concluded the combined incidence of syphilis was lower by two-thirds with doxycycline postexposure prophylaxis than with standard care.

Syphilis Outbreaks

Syphilis is a curable bacterial sexually transmitted infection (STI). If untreated, it can cause serious health issues, says the WHO. People can get syphilis by direct contact with a syphilis sore during vaginal, anal, or oral sex, and syphilis can spread from a mother with syphilis to her unborn baby. The U.S.Health Resources and Services Administration (HRSA), in partnership with the Indian Health Service (IHS), noted in July 2023 the rate of syphilis within highly impacted jurisdictions in Alaska, Arizona, Montana, Nebraska, New Mexico, Oregon, and South Dakota.

Japan's National Institute of Infectious Diseases reported 14,906 syphilis cases in 2023, a record high for the third consecutive year. Tokyo accounted for the most cases, with 3,658, followed by Osaka (1,967).

Syphilis News

January 10, 2024 - The U.S. FDA is allowing the importation of penicillin to combat increased syphilis cases in the U.S.

November 22, 2023 - The JAMA Network published - 90% of Congenital Syphilis Cases Could Have Been Prevented.

November 7, 2023 - The U.S. CDC published - Syphilis in Babies Reflects Health System Failures.

September 15, 2023 - Dr. Helen Fifer, senior author and lead microbiologist for bacterial sexually transmitted infections at the UK Health Security Agency, said in a press release, "We are seeing record levels of STIs (London), including syphilis."

April 2, 2023 - The Washington Post reported reasons syphilis is surging among the U.S.