An existing vaccine that prevents meningococcal disease may also be up to 40 percent effective at preventing gonorrhea infections, which are becoming increasingly resistant to antibiotics, with some strains completely incurable. This discovery is according to a series of studies and commentaries published Tuesday in The Lancet Infectious Diseases.
Though the estimated effectiveness is modest, shots of the vaccine—4CMenB aka Bexsero—could still prevent many infections, researchers reported. The vaccine could prevent more than 100,000 gonorrhea infections over 10 years in the UK, saving an estimated $10.4 million. In the meantime, the vaccine’s effectiveness could provide significant clues for vaccine developers to make a more effective gonorrhea-specific shot.
The need for such a vaccine is clear. Not only is gonorrhea quickly becoming more drug-resistant, but it also is on the rise in the US and other countries. The World Health Organization estimates there were more than 82 million gonorrhea cases worldwide in 2020. The US Centers for Disease Control and Prevention estimates there were nearly 680,000 cases in the US in 2020, up 10 percent from 2019 and up 45 percent from 2016.
In a press conference Tuesday, Jonathan Mermin, director of the CDC’s National Center for HIV, Viral Hepatitis, STD, and TB Prevention, highlighted the optimism around using 4CMenB to prevent gonorrhea. “There’s more research going into that,” Mermin noted, “But it does show at least some hope that in the future we could be developing effective and safe vaccines against gonorrhea, which would help us more successfully reverse some of the trends that we’ve been seeing over the past ten years.”
The effectiveness of a meningococcal vaccine against gonorrhea stems from the fact that the two diseases are caused by related bacteria—Neisseria meningitidis and Neisseria gonorrhoeae, respectively. Previous research has suggested that the vaccine could provide cross-reactive immune responses, given that the two microbes share significant amounts of their genetic code and key proteins targeted by the vaccines.
In the series of studies published Tuesday, two were case-controlled observational studies looking at the real-world effectiveness of 4CMenB against gonorrhea infections in specific populations in the US and Australia.
In the US-based study, led by the CDC’s Winston Abara, researchers used health records of gonorrhea cases in people ages 16 to 23 in New York City and Philadelphia from 2016 to 2018. The cases were matched to others in the same age group who had chlamydia — the control group.
The researchers had records of nearly 168,000 infections (approximately 18,000 gonorrhea infections, 125,000 chlamydia infections, and 25,000 co-infections) among almost 110,000 teens and young adults. Of those, nearly 7,700 were vaccinated with at least one dose—about 4,000 had one dose, and 3,600 had two doses. The researchers estimated that having two doses provided 40 percent protection against gonorrhea, and one dose was 26 percent effective.
In the second study, Australian researchers tapped into data on more than 53,000 teens and young adults who received one dose and 46,000 who received two doses in South Australia as part of a statewide program. Looking at the vaccination status of gonorrhea cases and using chlamydia cases as controls, the researchers estimated that the 4CMenB vaccine was 33 percent effective at preventing gonorrhea.
The studies have several limitations. For instance, the researchers cannot determine how long such protection may last against gonorrhea after vaccination. The studies looked at specific populations, so the estimates may not be generalizable. Still, any modest benefits could significantly impact disease spread, especially in high-risk groups, such as young adults and men-who-have-sex-with-men (MSM).
In a third study released Tuesday, researchers in the UK modeled the cost-effectiveness of using the meningococcal vaccine 4CMenB to prevent gonorrhea infections. They estimated that vaccinating at-risk MSM could prevent 110,000 cases in the UK over the next 10 years, saving $10.4 million in testing and treatment costs. And those estimates are conservative. The researchers assumed that one dose of the vaccine does not provide any protection. The study also didn’t account for extra costs that may be associated with drug-resistant gonorrhea infections.
“With a gonorrhea-specific vaccine likely to take years to develop, a key question for policymakers is whether the meningitis vaccine 4CMenB should be used against gonorrhea infection,” lead author of the modeling study, Peter White, of Imperial College London said in a statement. “Our analysis suggests that giving the vaccine to those at the greatest risk of infection is the most cost-effective way to avert large numbers of cases.”