Herpes simplex virus (HSV) belong to the family of herpesviruses. They are very common — they affect around 90% of adults globally. And they can lead to painful sores anywhere in or around the mouth and genital area.
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There is no cure for HSV infections, and people have to manage their outbreaks by taking antiviral medications. A number of HSV vaccines have been studied. But none have yet come to market.
But companies are already struggling to work out how to avoid these infections through vaccination, and with good reason. A vaccine to protect people from becoming infected with the virus that most commonly causes genital herpes is being tested in humans. Modelling shows that such a vaccine could prevent about 350,000 new infections per year.
There are a number of these pending HSV vaccine candidates. The theory is that they’ll show potential where other promising specimens haven’t. We will cover recent and continuing research in this area and whether we can anticipate the availability of a vaccine anytime soon.
What is the Herpes Simplex Virus (HSV)?
HSV is a virus that can cause sores (”lesions”) in your mouth or in the genital area, as well as a painful infection around the mouth (“cold sores”). The two primary herpes simplex viruses are HSV-1 and HSV-2. HSV-1 infections typically occur around your mouth, but they can cause sores in your genitals. HSV-2, on the other hand, is most often found on or around your genitals.
After you get infected with HSV, the virus remains in your body for your entire life. This can cause sores or blisters to form from time to time (outbreaks). In very rare instances, it can lead to life-threatening infections, including meningitis and encephalitis.
When you think of herpesviruses, you probably think of HSV. But both types of HSV are actually members of a larger family of herpesviruses, which are:
- Varicella-zoster (causes chickenpox and shingles)
- Epstein-Barr virus (causes mononucleosis)
- Cytomegalovirus
Is There a Cure for Herpes?
The bad news: There’s no cure for herpes right now. Scientists hope that gene therapy could lead to a breakthrough in curing herpes. Thus far, the results in animal models look promising.
In the meantime, treatment for HSV infections is addressed with prescription antiviral drugs, such as Valtrex (valacyclovir) or Zovirax (acyclovir). There are medications to clear up blisters when and if they occur. And some people also take them daily to prevent outbreaks.
But some people could discover that existing medications don’t go far enough in alleviating those symptoms. And condoms may not cover all sites of genital blisters, since they can show up in the genital area not covered by a condom, where the condom may not completely cover the affected area, preventing transmission to your partner. This has led to investigations regarding the development of a vaccine for these viruses.
Why is Creating an HSV Vaccine so Difficult?
Herpesviruses can reside in your body without being recognised. This is why your immune system doesn’t respond to them right away. The later one detects the virus, the harder it is to make an effective vaccine.” We have vaccines for other diseases caused by herpesviruses, like chickenpox and shingles, but HSV is more effective at hiding from the immune system.
When scientists create vaccines, they take aim at the part of your immune system that tells an intruder — a virus or bacteria — that it doesn’t belong in your body. The vaccine then trains your body to kill the invader before it renders you ill. No amount of vaccine magic can train your body to defend itself if the immune system is not going to respond to HSV in the first place.
Animal studies have yielded promising results in trials of HSV vaccines. But when tested in humans, these vaccines didn’t perform as well. Pharmaceutical companies—if they wanted to try again—then had to restart their research efforts.
Has there Ever Been an HSV Vaccine Tested on Humans?
Yes. There have been human trials of multiple vaccines in recent years. Vaccine trial participants didn’t experience very many side effects.
But they didn’t reap much reward, either. While prior studies fared badly, several vaccines remain under testing.
Is There a Vaccine in Research for Herpes (HSV)?
Yes, there are vaccines in development for both HSV-1 and HSV-2. Most are being studied in HSV-2. But because the viruses are so similar, a vaccine against HSV-2 would likely also work against HSV-1, Marquez said.
Two different vaccines that are being studied for HSV are:
Therapeutic vaccines: These would help people who have already been infected with HSV. They might improve symptoms, contribute to faster healing of blisters and reduce the risk of passing the virus on to others.
Preventative vaccines: These would help those who do not have HSV exposure yet. They would teach your immune system to fend off an HSV infection if you were exposed to the virus in the future.
Like all vaccines, any HSV vaccine will have to pass three kinds of clinical trials — phase 1, 2, and 3 — before the F.D.A. gives it the all clear.
This is so that we can ensure that they are safe and effective for humans. This process can take years. Which means a HSV vaccine is likely a long way off.
Here are some HSV vaccine candidates in development today:
1. mRNA-1608
Utu recognizer Messenger RNA (mRNA) technology also has potential for vaccines against certain kinds of infections — including HSV. Moderna is working on an HSV-2 aptamer-complexed mRNA therapeutic vaccine called “mRNA-1608.”
The mRNA-1608 vaccine is currently being investigated in a phase 1/2 clinical trial in 18-to 55-year-old adults with a history of recurrent HSV-2 genital herpes. Scientists are trying several doses to see whether they are safe and induce an immune response. The trial is due to be finished in June 2025.
2. BNT163
BioNTech’s HSV-2 vaccine (BNT163) is also moving forward. It is based on mRNA technology to prevent infection. The company began a phase 1 clinical trial in December 2022 for the vaccine in adults 18 to 55 years with no known history of symptomatic genital herpes. The trial is due to finish in December five years later.
3. RVx-201
RVx-201 is a therapeutic vaccine candidate that was created by Rational Vaccines. In an animal study, it was found to reduce the frequency of symptomatic days by 45%, compared with only 24% for another HSV vaccine. It also decreased recurring genital herpes sores.
The company began a vaccine candidate trial in 2022. The goal of the study is to assist researchers as they seek to establish the baseline attributes of a participant and their willingness to enroll in a clinical trial.
The research has already been concluded, but no new release has been provided. The company is also developing prophylactic vaccines for HSV-2 (RVx-2001) and HSV-1 (RVx-1001).
The Bottom Line
Efforts are in progress to discover vaccines that can be used in therapy or prophylaxis against herpes simplex virus (HSV) infection. Millions of people would use HSV vaccines. For vaccines to be safe and effective, they need to go through a series of steps before they are approved.
Previous vaccines have failed in humans, but researchers keep searching in other corners for something that works. Because we are getting better at understanding HSV infections and how they function, an eventual vaccine is foreseeable.
