There is no vaccine available for trichomoniasis in humans. No candidate has reached FDA approval or advanced to late-stage clinical trials, despite trichomoniasis being the most common curable sexually transmitted infection worldwide, with roughly 156 million new cases each year. Research into a human vaccine is active but still in early stages, and the parasite’s biology makes development unusually difficult.
Why a Vaccine Has Been So Hard to Develop
Trichomonas vaginalis is a parasite, not a virus or bacterium, and that distinction matters enormously for vaccine design. Parasites are larger, more complex organisms with sophisticated ways of dodging the immune system. T. vaginalis uses a diverse and constantly shifting set of surface proteins to attach to vaginal tissue, destroy cells, and evade immune detection. The parasite essentially changes its appearance depending on what it encounters, making it a moving target for any immune response a vaccine might generate.
Another challenge is location. The infection lives on mucosal surfaces, the moist tissue lining the genital tract. Generating a strong, lasting immune response at mucosal sites is harder than in the bloodstream, which is where most traditional vaccines work best. Researchers still don’t fully understand how the human immune system naturally responds to trichomoniasis, and that basic knowledge gap slows vaccine design. A grant from the National Institutes of Health, led by researcher Frances Mercer at Cal Poly Pomona, is specifically studying how immune cells interact with the parasite, including whether a vaccine should aim to trigger antibody production or activate a different arm of immunity entirely.
What Researchers Are Studying
Several parasite proteins have been identified as potential vaccine targets. One of the most studied is a protein called TvAP65, which helps the parasite attach to human cells. In lab experiments, animals given antibodies against TvAP65 showed reduced infection severity, and the protein has been tested as a candidate vaccine antigen in early research. Another protein, TvCP39, plays a role in how the parasite causes damage during infection and is being explored as both a drug target and a vaccine component.
These are promising leads, but all of them remain in preclinical stages, meaning they’ve been tested in lab settings or animal models rather than in human trials. The jump from identifying a target protein to producing a safe, effective vaccine that works in people typically takes many years, even when funding is strong.
A Cattle Vaccine Exists, but It’s Different
Interestingly, there is a licensed vaccine for a closely related infection in cattle. TrichGuard is a killed whole-cell vaccine used to protect cows against Tritrichomonas foetus, a parasite that causes infertility and pregnancy loss in herds. In a controlled study, 95% of vaccinated heifers became pregnant after exposure to the parasite, compared with 70% of unvaccinated animals. Among those that carried to term, 50% of vaccinated heifers delivered a live calf versus just 20% of unvaccinated ones.
The cattle vaccine doesn’t prevent infection entirely. Instead, it reduces the severity of reproductive complications. This is a useful model for human researchers because it shows that even partial immune protection can have meaningful health benefits. However, the bovine parasite is a different species, cattle reproductive tracts differ from human ones, and regulatory standards for human vaccines are far more stringent, so TrichGuard can’t simply be adapted for people.
Why a Vaccine Would Matter
Trichomoniasis is treatable with antibiotics, but treatment alone hasn’t controlled the epidemic. The CDC notes a high rate of reinfection among treated women and recommends retesting three months after treatment regardless of whether a partner was also treated. Reinfection happens frequently because treatment doesn’t create lasting immunity: you can catch it again immediately.
The scale of the problem is staggering. The World Health Organization estimated 156 million new infections globally in 2020, split nearly evenly between women (73.7 million) and men (82.6 million). About a third of cases occur in Africa, followed by the Americas. Beyond the infection itself, trichomoniasis increases susceptibility to HIV, can cause complications during pregnancy, and contributes to chronic inflammation in the reproductive tract. A vaccine, even one that reduced severity rather than preventing infection outright, could have outsized public health impact.
Current Prevention Options
Without a vaccine, prevention relies on the same strategies used for other sexually transmitted infections. Consistent condom use significantly reduces transmission risk, though it doesn’t eliminate it entirely because the parasite can infect areas not covered by a condom. Limiting the number of sexual partners and ensuring both partners are tested and treated when an infection is found are the most effective approaches available.
If you’ve been treated for trichomoniasis before, the CDC’s recommendation to get retested at three months is worth following even if you’re confident your partner was treated. Reinfection is common enough that it’s considered routine rather than exceptional. Testing is simple, typically a swab or urine sample, and treatment with oral antibiotics usually clears the infection within a week.