Herpes Vaccine Candidates in 2027: Where Every Trial Stands

No herpes vaccine is approved, and none will reach the public in 2027. The field shrank over the past three years. GSK dropped its candidate in 2024, and Moderna stopped its mRNA vaccine in November 2025 even though early data showed it was safe and triggered immune responses.

That leaves BioNTech's BNT163 as the only herpes vaccine in clinical trials at a large drug company. A handful of smaller programs, mostly live-attenuated vaccines, are trying to reach their first human trials.

The nearer-term progress is in drugs rather than vaccines. A new antiviral, pritelivir, has an FDA decision due by the end of 2026, and Gilead plans to start a Phase 2 trial of a once-weekly herpes pill by the same date.

Below is the status of each candidate based on company announcements, trial registries and published data as of October 2026. For the broader picture, including why herpes is so hard to cure, see our 2027 herpes cure research overview.

BioNTech's BNT163 is the last big-pharma herpes vaccine in trials

BNT163 is an mRNA vaccine designed to prevent genital herpes (HSV-2) in people who have never been infected. It was developed with the University of Pennsylvania, building on years of work by Dr. Harvey Friedman's lab.

How BNT163 works

The vaccine encodes three HSV-2 surface proteins:

• gD, which the virus uses to enter cells
• gC, which helps the virus attach and blocks part of the immune response called complement
• gE, which the virus uses to disable antibodies

Older vaccines targeted gD alone and failed. The idea behind BNT163 is that blocking the virus's immune-evasion proteins as well as its entry protein gives antibodies a better chance to work. In lab studies in animals, the three-protein vaccine gave strong protection against genital infection.

What the trial has shown so far

The Phase 1 trial (NCT05432583) started in December 2022 and enrolled roughly 300 participants, including healthy volunteers and people with a history of recurrent genital herpes. Results presented at IDWeek in October 2025 and published in 2026 showed that BNT163 was well tolerated with an acceptable safety profile and produced binding and neutralizing antibodies against HSV-2.

The trial is scheduled to finish in October 2026. Phase 1 does not test whether a vaccine prevents infection. That needs a much larger efficacy trial, and BioNTech has not announced one.

Realistic timeline

If BioNTech moves forward, a Phase 2 or combined Phase 2/3 efficacy trial would likely take three to five years, since researchers need to wait for enough new infections among participants to compare groups. A preventive vaccine reaching the market before 2030 is unlikely.

The first people to benefit would be those who have never had HSV-2, such as young adults before they become sexually active and partners of people with HSV-2. A preventive vaccine would do little for people who already carry the virus.

Moderna stopped mRNA-1608 despite encouraging early data

mRNA-1608 was Moderna's therapeutic vaccine, meant to reduce outbreaks in people who already have HSV-2. Its Phase 1/2 trial (NCT06033261) enrolled about 300 adults with recurrent genital herpes and finished in April 2025.

Interim results, later published in Open Forum Infectious Diseases, showed:

• no major safety concerns, with most side effects mild or moderate
• increased binding and neutralizing antibodies against HSV-2 in every vaccine group
• exploratory trends toward a longer time to the next outbreak and fewer recurrences

On November 20, 2025, Moderna announced it would not take mRNA-1608 into Phase 3. The company framed it as part of a wider cut to research spending rather than a safety or efficacy failure.

For people with herpes, this was a real loss. The data suggested the vaccine might help, but without a Phase 3 trial it will not reach patients unless another company or funder picks it up. No buyer or partner has been announced.

GSK's vaccine failed because antibodies alone weren't enough

GSK's candidate, GSK3943104, was also a therapeutic vaccine for people with recurrent genital herpes. It used purified viral proteins with an adjuvant, the same approach behind GSK's highly successful shingles vaccine, Shingrix.

In September 2024, GSK announced that the Phase 2 part of its trial did not meet its efficacy objective and ended the program. The vaccine produced antibodies but did not reduce recurrences enough. Our report on the GSK decision has the details.

Many researchers see this as more evidence that controlling a virus that hides in nerve cells needs strong T-cell responses, especially tissue-resident T-cells in the genital skin, not just circulating antibodies. Protein-only vaccines are generally weaker at producing those T-cells than mRNA or live-attenuated vaccines.

Earlier protein vaccines failed for similar reasons. GSK's Herpevac (gD2) did not protect women against HSV-2 in a 2012 trial, and Genocea's GEN-003 was shelved in 2017 for commercial reasons despite modest benefits.

Live-attenuated vaccines are still trying to reach human trials

Live-attenuated vaccines use a weakened version of the herpes virus that can't cause disease. They expose the immune system to dozens of viral proteins instead of two or three, which tends to produce broader T-cell and mucosal immunity.

Rational Vaccines' RVx201

RVx201 is a live HSV-2 strain with a key gene (ICP0) disabled so it can't reactivate normally. It is based on research by Dr. William Halford, who died in 2017.

In February 2026, Rational Vaccines began collecting interest from volunteers for a planned Phase 1 trial in the UK. The trial has not been confirmed as enrolling or dosing participants. The main regulatory hurdle for any live herpes vaccine is showing that the weakened strain can't revert or cause harm in people with weak immune systems.

ΔgD-2 and other preclinical candidates

HSV-2 ΔgD-2, a strain missing the gD gene, gave strong protection in lab studies in animals, including a 2025 head-to-head comparison of three vaccine strains. Its developer, X-Vax Technology, ceased operations in late 2023, and the candidate's clinical future is unclear.

Researchers including Dr. Kening Wang at the NIH are also testing other weakened strains, such as HSV-2 gD27, in animals. None are in human trials.

New antivirals will arrive years before any vaccine

These are drugs rather than vaccines, but for most readers they matter more in the near term.

Pritelivir: FDA decision due by the end of 2026

Pritelivir, from Germany's AiCuris, is a helicase-primase inhibitor. It blocks a different viral enzyme from acyclovir and valacyclovir, so it works against resistant strains. In its key Phase 3 trial in immunocompromised patients with infections that weren't healing, 82.4% of patients on pritelivir achieved complete healing, versus 42.0% on other treatments.

The FDA granted Priority Review in April 2026, with a decision due in the fourth quarter of 2026. An approval would make it the first new herpes drug in more than 20 years, but initially only for this narrow group. Read more in our pritelivir guide.

Gilead's once-weekly pill: Phase 2 expected by the end of 2026

Assembly Biosciences developed two long-acting helicase-primase inhibitors, ABI-5366 and ABI-1179. In small 29-day Phase 1b trials in people with recurrent genital herpes, once-weekly doses cut viral shedding by 94% to 98% compared with placebo. For comparison, daily valacyclovir typically reduces shedding by about 70%.

Gilead licensed both drugs in December 2025. In August 2026 it chose GS-1179 (formerly ABI-1179) to advance, with a Phase 2 trial in recurrent genital herpes expected to start by the end of 2026. The other drug, GS-5366, remains licensed to Gilead but is not being developed for now.

Gilead's plan also considers testing GS-1179 for prevention, including alongside HIV pre-exposure prophylaxis (PrEP). In September 2026, Assembly opted to share 40% of US development costs and profits. Approval is unlikely before about 2030, and details are in our weekly herpes pill update.

Gene editing is still waiting for its first genital herpes trial

Vaccines and antivirals control the virus. Gene editing aims to remove it from nerve cells, which would be a true cure.

Dr. Keith Jerome's team at Fred Hutchinson Cancer Center in Seattle uses engineered enzymes called meganucleases, delivered by a harmless virus, to cut up dormant herpes DNA. In lab studies in mice, a single-vector version cleared about 90% of latent HSV-1 after oral infection and 97% after genital infection, with fewer side effects than earlier versions.

The team has said it hopes to begin human trials around 2026 or 2027, but no trial has been registered.

In China, BDgene's BD111 uses CRISPR to target HSV-1 in the eye, where the virus causes a serious condition called herpetic stromal keratitis. A Phase 2a trial (NCT06474442) with 40 patients began in April 2025 and compares BD111 plus standard treatment with standard treatment alone. Its primary completion date is December 2026, with final completion in March 2027.

Eye infections are a much easier target than nerve ganglia, so success there would not mean a genital herpes cure is close. Our BD111 report covers the earlier human results.

A third program, Excision BioTherapeutics' EBT-104, cut viral shedding in 92% of treated eyes in lab studies in rabbits. It has not entered human trials.

A "functional cure" is a more realistic near-term goal

Researchers increasingly talk about a functional cure rather than complete elimination of the virus. A functional cure would leave dormant viral DNA in the nerves but keep it so well controlled that a person:

• no longer gets symptomatic outbreaks
• sheds little or no virus
• has a very low chance of passing it to partners

A strong therapeutic vaccine, a long-acting antiviral, or a combination of both could achieve this. The Phase 1b shedding results for Gilead's weekly pills are the closest anything has come so far, although only over a few weeks.

Even partial protection would help millions. WHO estimates that about 3.8 billion people under 50 have HSV-1 and around 520 million people aged 15 to 49 have HSV-2, and our 2027 herpes statistics page covers the latest figures.

Natural infection shows how far partial protection can go. Having HSV-1 does not stop people catching HSV-2, but a first HSV-2 outbreak tends to be milder in people who already carry HSV-1. Our article on whether HSV-1 protects against HSV-2 explains why.

Daily suppressive therapy is the best option while research continues

If you have genital herpes and frequent outbreaks, daily suppressive therapy with valacyclovir, acyclovir or famciclovir cuts outbreaks by 70% to 80% and roughly halves the risk of passing HSV-2 to a partner. It is cheap, generic and well studied.

To join a trial, search ClinicalTrials.gov for "herpes simplex" and filter for "Recruiting." Therapeutic trials need people with confirmed HSV-2. Prevention trials need people who test negative.

Be wary of anyone selling a "herpes vaccine" or "cure" online. Nothing on this list is available outside a clinical trial or an expanded access program run by a doctor.

We review this page every six months. For a broader overview of cure research, see our herpes cure research update.