As gonorrhea becomes untreatable, a repurposed vaccine may prevent it

An existing vaccine that prevents meningococcal disease may be up to 40 percent effective at preventing gonorrhea, which are becoming increasingly resistant to antibiotics. A series of studies and commentaries were published Tuesday in The Lancet Infectious Diseases.

Researchers reported that the vaccine could still prevent many infections. The vaccine could prevent more than 100,000 gonorrhea infections in the UK over the course of 10 years. The effectiveness of the vaccine could provide clues for the development of a more effective gonorrhea-specific shot.

There is a clear need for such a vaccine. Gonorrhea is on the rise in the US and other countries. More than 80 million gonorrhea cases are estimated by the World Health Organization. The US Centers for Disease Control and Prevention estimates there were over 680,000 cases in the US in 2020.

Jonathan Mermin, director of the CDC's National Center for HIV, Viral Hepatitis, STD, and Tuberculosis Prevention, highlighted the optimism around using 4C MenB to prevent gonorrhea.

The effectiveness of a meningococcal vaccine against gonorrhea is due to the fact that the two diseases are caused by the same bacterium. The vaccine may be able to provide cross-reactive immune responses due to the fact that the two microbes share significant amounts of their genetic code.

Multipurpose vaccine

Two of the studies published Tuesday looked at the effectiveness of 4C MenB against gonorrhea infections in specific populations in the US and Australia.

In the US-based study, researchers used health records of gonorrhea cases in people ages 16 to 23 in New York City and Philadelphia. The cases were compared to others in the same age group who had the disease.

The researchers had records of over 168,000 infections among teens and young adults. About 4,000 had one dose, and 3,600 had two. 40 percent protection against gonorrhea was provided by two doses, and 26 percent by one dose, according to the researchers.

More than 53,000 teens and young adults received one dose and 46,000 received two in South Australia as part of a statewide program in the second study. The researchers estimated that the 4C MenB vaccine was 33 percent effective at preventing gonorrhea, based on the vaccination status of gonorrhea cases and the use of chlamydia cases as controls.

There are several limitations to the studies. The researchers can't say how long the protection will last against gonorrhea. The estimates may not be generalizable because the studies looked at specific populations. The impact of disease spread in high-risk groups, such as young adults and men-who-have-sex-with-men, could be significantly impacted by any modest benefits.

Researchers in the UK modeled the cost-effectiveness of using the meningococcal vaccine 4C MenB to prevent gonorrhea infections. Over the next 10 years, they estimated that the vaccine could prevent over 100,000 MSM cases in the UK. The estimates are conservative. The vaccine does not provide any protection, according to the researchers. Extra costs that may be associated with drug-resistant gonorrhea were not included in the study.

With a gonorrhea-specific vaccine likely to take years to develop, a key question for policymakers is whether the 4C MenB vaccine should be used against gonorrhea.