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Why the Progress of STI Vaccines Is Still So Maddeningly Slow

The bleak and horrifying truth? Science can’t seem to evolve faster than the infections

As of 2018, STI rates in the U.S. were on the rise for the fourth year in a row. According to a report released by the Centers for Disease Control and Prevention (CDC) last August, gonorrhea transmission increased 67 percent, syphilis cases almost doubled and the overall rate of STD transmission reached an all-time high. 

“We’re really getting a little desperate. We need a vaccine that would prevent those illnesses,” says William Schaffner, professor of preventive medicine at the Vanderbilt University School of Medicine. Especially because, he adds, “many patients have minimal or no symptoms. That means those individuals are capable of passing on these infections to others undetected. That’s part of what maintains these infections in our population and makes them so easy to spread.” 

Obviously, a lack of vaccines isn’t because of a lack of effort. Science just can’t seem to evolve faster than the infections, which is why, for example, antibiotics aren’t treating gonorrhea as effectively anymore. Basically, researchers are playing a constant game of catch-up and failing more often than not. Or as Schaffner puts it, “We’ve had many attempts at creating vaccines for [STIs], but none of them have consummated in a successful vaccine yet.”

To find out exactly how far away the science is, I recently spoke to Schaffner about the state of vaccine development for the most common STIs and the challenges facing each. Here’s what he had to say… 

Hepatitis B

Let’s first start with the positive. Hepatitis B vaccines originally emerged in the 1980s, with a trio of options becoming commercially available in 1982, 1986 and 1989, respectively. “We don’t think of hepatitis B in the category of STDs, but it’s most commonly transmitted through sexual intimacy,” Schaffner explains. However we classify it, though, he adds, “we have several very effective vaccines against it that are safe, effective and widely implemented. As such, we’ve made a huge impact on the occurrence of hepatitis B.” In fact, infants often receive their first dose of the Hepatitis B vaccine at birth.


Schaffner prefers referring to the human papillomavirus (HPV) vaccine as an anti-cancer vaccine — more because of the conservatism of parents than necessarily the science. “When we think about STIs, we think about illnesses in the genital tract at the reproductive organs, but HPV causes cancers in a different anatomic location,” Schaffner explains. “Presenting it as an anti-cancer vaccine is the truest way of looking at it. When that vaccine was originally introduced, it evoked a lot of resistance on the part of parents. I think we put the focus on the wrong thing by emphasizing how the virus is acquired rather than saying, ‘We’ve been looking for an anti-cancer vaccine for decades, and now we have one.’” 

Either way, like the hepatitis B vaccine, the HPV vaccine has greatly minimized cases of HPV and its related precancerous lesions since it was first introduced in 2006.


Every time you get gonorrhea, you run the risk of it getting into the bloodstream and producing a serious illness throughout the whole body. Plus, Schaffner says, “You can get gonorrhea, have it treated, get it again, treat that and get it again. That means that the body’s immune system in the natural state doesn’t effectively create a natural protection once you’ve had the gonorrhea infection. It’s not like measles where you get it once, and you’ll never get it again — no matter how often you’re exposed throughout your life. And so, for a gonorrhea vaccine to be effective, we have to do something different than what happens in nature. That’s always a much larger challenge.” 

Ann Jerse, a professor in the Department of Microbiology & Immunology at the Uniformed Services University of the Health Sciences, is currently confronting that challenge head-on — with the help of a $10.7 million National Institutes of Health (NIH) grant and researchers from Duke University, the University of Virginia, the University of North Carolina, Emory University and the University of New Mexico. In particular, they’re collaborating to establish the Gonorrhea Vaccine Cooperative Research Center, where they hope to create a gonorrhea vaccine safe for human trials by late 2024. 

Chlamydia and Herpes

Chlamydia is the most common bacterial STI in the world. While it can be treated with antibiotics, untreated chlamydia can have negative health consequences such as reactive arthritis and infertility. And though herpes is a virus, not a bacterial infection, a successful vaccine will have to share certain functionality with a chlamydia vaccine. “The trick for chlamydia and herpes is to create a vaccine that’s sprayed on mucus membrane surfaces that will engage with the virus and prevent it from establishing an infection. And that’s very, very hard to do scientifically because of the nature of the mucus membrane,” Schaffner explains. 

So hard that we’ve been attempting to do so for 70 years with no luck. Per one academic overview: “This review has identified that, in over 70 years of vaccine research, with many advances in techniques and knowledge of the target species, no single antigen type or target, adjuvant or route of administration has been established as a clear frontrunner for effective vaccination. Extensive mouse model trials indicate that whole cell antigenic targets induce an effective response, protecting from disease and reducing shedding rates. However, replication of these results using more commercially acceptable antigenic preparations has proven difficult.”

Not that we’ve stopped trying. In May, the University of North Carolina and its partners received nearly $11 million from the NIH and National Institute of Allergy and Infectious Diseases to create a Chlamydia Vaccine Initiative research center. The hope, of course, is that it won’t take another 70 years before we develop some better answers.


The search for an HIV cure has been ongoing since the disease’s initial outbreak in the early 1980s. “The major problem is that the virus keeps changing,” Schaffner explains. “It mutates at an extraordinarily rapid rate, and so, we haven’t yet created a formula. Although we think we’re getting closer scientifically to being able to create a protection against the virus.” 

This kind of vaccine would work differently than pre-exposure prophylaxis (or PrEP), the antiviral medicine that’s been effective in preventing people from becoming HIV positive. “A vaccine is designed to stimulate the immune system to prevent an infection from actually occurring; antivirals are more akin to an antibiotic used to treat an infection after you’ve got it,” Schaffner tells me. “PrEP provides firewall substance in the tissue so that the moment the virus encounters PrEP, it gets killed. But you have to have that drug on board, in your system in a sufficient dose, in order for it to encounter the virus and prevent transmission of the disease.” 

In terms of a vaccine, there are at least 22 ongoing studies currently active. And Johnson & Johnson is set to begin testing an HIV vaccine in Europe and the U.S. later this year. Results are expected by 2023, with the intention of creating a vaccine ready for a clinical, human trial within five years of that. 

Overall, for any of the aforementioned vaccines, the road may be weary, but Schaffner vows, “I’m more excited about the potential for the next decade of developing vaccines against STIs than I’ve ever been before. So now is the time to invest that research money, because the science may actually be ready to help with this sort of breakthrough.”