Vaccinations for chlamydia, gonorrhea and syphilis — will they ever be a reality? We take a look at what’s happening the world of STI vaccination research.
We know it can be done. Vaccinations have been successfully developed for bacterial infections including cholera, tuberculosis and tetanus, and viral infections from the human papilloma virus (HPV) types 16 and 18 to hepatitis A and B.
So, is the same thing possible for STIs like chlamydia and gonorrhea, currently among the most common infections in the world?
The good news is that research is underway (and has been for decades) to develop vaccines to prevent many of these infections. Are we getting closer to the possibility of a future without these STIs?
Vaccine: in development
Chlamydia is a bacterial infection which affects 113 million people globally each year — it’s the most commonly diagnosed bacterial STI in the USA and also in Australia. Symptoms can include pain when urinating and unusual discharge from the penis or rectum, but in 50 per cent of men and 70-80 per cent of women, it has no symptoms at all. It’s passed on during condomless oral, anal or vaginal sex with someone who has acquired it.
Chlamydia is caused by Chlamydia trachomatis bacteria, and it’s currently treated very effectively with antibiotics. But chlamydia has outsmarted every attempt at a vaccine for over 30 years.
“Chlamydia is caused by Chlamydia trachomatis bacteria, and it’s currently treated very effectively with antibiotics.”
But recent developments may change the status quo. In July 2016, researchers at McMaster University in Ontario published breakthrough research in the development of a chlamydia vaccine in mice. Their work combined proteins from three variants of C. trachomatis bacteria into an antigen called BD584. In mice, BD584 reduced chlamydial ‘shedding’, a common symptom, by 95 per cent, making it a very promising candidate for a human chlamydia vaccine.
While there’s no expected date for a widespread chlamydia vaccine (human trials have not even begun yet), this is a significant step forward and the research is ongoing.
And the best part? No needles. The BD584 vaccine is given with a nasal spray.
Vaccine: research underway
Another stubbornly common bacterial infection, gonorrhea affects around 78 million people globally every year. Symptoms can include pain when urinating, unusual discharge from the penis or rectum, and a sore throat, though many men and most women don’t have any symptoms at all. Gonorrhea is spread by having condomless vaginal, anal or oral sex with a person who has acquired it.
Gonorrhea is caused by the Neisseria gonorrhoeae bacterium. N. gonorrhoeae is getting harder to treat with antibiotics, partly because it mutates faster than a Ninja Turtle and can acquire resistance from other bacteria.
Hope has arrived from across the Tasman. Researchers in New Zealand recently ran a study with 15,000 young people, with some unexpected results. Published in July 2017, their study found that gonorrhea infections were 31 per cent less likely in those who had been immunised against meningitis between 2004 and 2006. It showed that the meningococcal B vaccine provided a level of ‘cross-protection’ against gonorrhea, because of similarities between the bacteria which cause the two infections. The mechanism behind the cross-immunity is not yet understood, but protection seemed to last about two years.
“…for people who are currently on HIV treatment, STIs appear to have no or very little impact on viral load.”
Unfortunately, the meningitis vaccine in question is no longer available. But it’s the only thing close to a gonorrhea vaccine ever discovered, and further research is already underway.
Vaccine: successful animal trials, research underway
Syphilis has been the focus of eradication campaigns by both the Centre for Disease Control (CDC) in the USA, and the World Health Organisation (WHO). But it remains in circulation in most of the world, and acquisition rates have actually been growing, particularly among men who have sex with men. Syphilis has multiple stages of infection and, if left untreated long-term, can cause damage to almost any part of the body. For people living with HIV who aren’t on treatment, having an STI such as syphilis can cause an increase in viral load. However, for people who are currently on HIV treatment, STIs appear to have no or very little impact on viral load.
Syphilis has been treated with the antibiotic penicillin for over 70 years. Unlike gonorrhea, syphilis has not acquired significant resistance to first-line antibiotics. However, globally high rates of syphilis persist, making vaccination an increasingly important priority.
“Syphilis has been treated with the antibiotic penicillin for over 70 years.”
In fact, research has already produced an effective vaccine in rabbits. While the methods in the original successful animal model couldn’t be used for humans (60 injections over 37 weeks, anyone?) further research in Canada this year has produced a promising candidate for a new vaccine. Three injections at three-week intervals successfully produced immunity in rabbits.
Again, human trials haven’t started yet, but we’re a step closer than we’ve ever been.
So, can we expect any of these vaccines anytime soon?
It may come down to money. The average timeline for development of a new vaccine is 8–18.5 years, at an estimated cost of USD $200–$900 million. Securing funding for this sort of research can be difficult, as these infections are not usually life-threatening, and more serious diseases often take priority (ebola, for example).
In the meantime, knowledge is power! Get informed about ways to protect yourself and your partner against these and other STIs. And go see your doctor, even if you don’t think you need to — getting checked regularly (and treated if necessary) is still one of the best ways to stop the spread of STIs.