Sexually Transmitted Disease Vaccine Development Remain Underwhelming

The U.S. Sexually Transmitted Infections (STI) National Strategic Plan includes, but is not limited to, vaccine and treatment research focused on chlamydia, gonorrhea, and Mpox.

According to recent STI reports, additional clinical evaluations and research are needed for these diseases.

For example, the U.S. Centers for Disease Control and Prevention (CDC) today announced a report describing New York City patients with Mpox who developed new lesions after completing oral treatment.

This CDC report suggests that post-treatment lesions might occur more commonly than previously reported.

During the 2022 Mpox outbreak in the U.S., TPOXX® (tecovirimat), an antiviral medication approved for the treatment of smallpox, was used as an investigational treatment for severe mpox.

However, efficacy and optimal treatment duration are still being investigated in 2023.

All ten patients received outpatient treatment from their healthcare provider with oral dosing of TPOXX, and all completed the recommended 14-day course.

Unfortunately, new Mpox lesions appeared a median of 13 days after completion of TPOXX treatment (range = 2–30 days).

In eight patients, the provider rated post-treatment lesions as less severe than initial lesions (median severity score = 3 [range = 3–7]).

One received a positive result among six patients for whom orthopoxvirus testing of post-treatment lesions was conducted.

One possibility to explain this analysis is that the Mpox virus, like other viruses, can recur, but the recurrent viral load might be too low for test detection.

And the proportions of patients not tested for STIs at initial Mpox diagnosis and the assessment of post-treatment lesions represent missed opportunities to identify potential coinfections or alternative diagnoses.

Two patients received repeat STI testing; one received a positive syphilis test result.

The immunocompromised patient with untreated HIV received positive post-treatment orthopoxvirus and positive syphilis test results.

TPOXX was restarted for two patients (one treated for seven additional days and one treated for 14 additional days), both of whom had resolved their lesions.

Among the seven patients who did not receive a second course of tecovirimat, six had a resolution of lesions.

Furthermore, Mpox vaccine breakthrough cases have been confirmed in 2023.

Public Health France published an update on March 23, 2023, confirming multiple cases of Mpox in previously JYNNEOS® (MVA-BN) vaccinated men in the Centre-Val de Loire region. 

And The Lancet published a clinical episode of a second Mpox virus infection in a fully vaccinated man. 

Recently, a study published in February 2023 concluded that chlamydia and gonorrhea cause substantial lifetime quality-adjusted life-years lost among infected women. 

As of April 27, 2023, no U.S. Food and Drug Administration vaccines are approved to prevent chlamydia or gonorrhea infection. But researchers are evaluating vaccine candidates in development.

Blue Water Vaccines Inc. announced the signing of a Sponsored Research Agreement with The University of Texas Health Science Center at San Antonio on April 12, 2023, to fund a non-human primate study to evaluate the efficacy of BWV-401, a live attenuated, orally delivered chlamydia vaccine candidate.

And regarding gonorrhea, the NEJM journal published Original Research on April 6, 2023, that found the incidence of gonorrhea was low with doxycycline postexposure prophylaxis.

And a study published in Clinical Infectious Diseases on June 1, 2022, suggests that a meningococcal serogroup B vaccine may offer cross-protection against gonorrhea infection. In France, MenB-4C vaccination is currently recommended against gonorrhea.

In summary, STI cases increased between 2020 and 2021, impacting millions.

To reverse this trend, the CDC calls for more local, healthcare, industry, and public health groups to contribute to STI prevention and treatment efforts.

Updated: Corrected headline, trademark, and related links on May 11, 2023.