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State of the evidence: October 2026

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A plain-language look at where herpes vaccine research stands, as of 21 October 2026. No tracked trial changed status this month, the trial that is furthest along is still a small early safety study in people, and two university vaccines that have only been tested in mice were added to the tracker.

This is a monthly look at the whole field. It reports what changed and what did not. It does not rank vaccines, and it does not guess when, or whether, any of them will work. Herpes simplex virus (HSV) comes in two types: HSV-1, which most often causes cold sores, and HSV-2, which most often causes genital herpes. Both can cause either. We say which type each item is about.

What changed this month

  • No tracked trial changed status. We checked the 18 trials in ClinicalTrials.gov (the US government’s public list of clinical trials) that belong to the vaccines we follow. None moved to a new phase, stopped, or posted results. One record had only its “last edited” date change, which tells us nothing new. The search for new HSV vaccine trials found none.
  • We re-checked our three most-read pages. These cover BNT163, mRNA-1608 and the University of Pennsylvania mRNA vaccine. The mRNA-1608 page needed no corrections. The BNT163 page had the trial design incomplete: it left out a part of the trial for people who already have recurrent genital herpes. We fixed that. The Penn page gained two 2026 studies in mice (see below).
  • We added two vaccines that have only been tested in animals. ΔgD-2 (from Albert Einstein College of Medicine) and the gG-2 vaccine (from the University of Gothenburg) have published results in mice only. We found no registered human trial for either.
  • The candidates table now shows whether a registered trial is ongoing. This comes straight from the trial registry and is dated. It is separate from our own description of each vaccine’s stage.

What we now know

  • BNT163 is still in an early trial, and the results so far are small. BNT163 is a vaccine from BioNTech, designed to prevent genital herpes (HSV-2, and possibly HSV-1) before someone is infected. Its trial is “phase 1” (a small first safety test in people). The registry lists 318 participants and says the trial is active but no longer recruiting. The only results published so far are a short conference summary of early safety and immune-response findings. A conference summary has not been through the full review that a journal paper goes through. It does not show whether the vaccine prevents herpes.
  • mRNA-1608 has stopped, and the reason given is a business one. This was Moderna’s vaccine for people who already have HSV-2 infection. Its phase 1/2 trial (a first safety test that also looks at early signs of whether it works) finished in April 2025. In November 2025 Moderna said it would not take the program forward. The reporting we have describes this as a company-wide decision about priorities, not a reported safety problem or a failed trial. A program that stopped is not the same as one that failed, and neither is the same as one that worked.
  • The Penn vaccine works in animals. That is all we know. Two 2026 papers report that mice were protected. One tested one part of the vaccine against HSV-2. The other tested the full three-part vaccine against an HSV-1 eye infection. BioNTech’s BNT163 is the version of this approach being tested in people. Mouse results do not show what will happen in people.
  • The two new additions are mouse studies. The ΔgD-2 vaccine uses a weakened HSV-2 virus that can enter cells once but cannot spread. Mouse studies report protection against both HSV-1 and HSV-2 disease. The gG-2 vaccine uses a surface protein found only on HSV-2, and mouse studies report protection against HSV-2. Neither has safety data in people.

What we still don’t know

  • Whether any herpes vaccine prevents or treats herpes in people. No tracked vaccine has published results from a large trial that tests this.
  • Whether BNT163’s trial is on schedule. Its registry record has not been edited since October 2025, so the dates on it may be out of date. We could not check BioNTech’s own announcements this month because the company’s site was not reachable from the tools we use.
  • Whether Moderna’s decision was only about priorities. Our source for the mRNA-1608 stop is a news report. We could not reach Moderna’s own announcement to confirm its wording. A news report alone is not enough for a status claim under our rules, and the company’s own statement is not yet on the page.
  • Whether a vaccine has been approved anywhere. We saw an unconfirmed report that an HSV-2 vaccine had been approved in China. We could not find a regulator record, a trial registry entry or a company filing to back it up, so we do not list it. Our rules require one of those before a status claim goes on this site.
  • Whether the two new mouse vaccines have a developer or any plan for human testing. We found no primary source for either.

What to watch next

Only items that already have a date on a public record:

  • BNT163 trial: registry estimate of October 2026 for “primary completion.” That is the date the registry estimates the last participant will finish the part of the trial that measures the main goal. It is a registry estimate, not a promise, and the record has not been updated since October 2025. It does not mean results will be published then. We will report if the record changes.

Nothing else we track has a scheduled date.

Every source for this update is listed below. If you spot an error, see the About page for how to tell us.

Sources

  1. A Clinical Trial in Healthy Volunteers and Volunteers With Recurrent Genital Herpes to Study the Safety, Tolerability, and Immune Responses After Vaccination With an Investigational Vaccine Designed to Prevent Genital Herpes Lesions (NCT05432583) — ClinicalTrials.gov , Active, not recruiting; record last updated 2025-10-20; checked 2026-10-21
  2. A Study of mRNA-1608, a Herpes Simplex Virus-2 (HSV-2) Therapeutic Candidate Vaccine, in Healthy Adults With Recurrent HSV-2 Genital Herpes (NCT06033261) — ClinicalTrials.gov , Completed April 2025
  3. Safety and Immunogenicity of BNT163, a Trivalent mRNA HSV Vaccine Candidate for Genital Herpes (abstract P-105) — Open Forum Infectious Diseases (IDWeek 2025) , October 2025
  4. HSV-2 gC2 mRNA immunization in mice protects by producing antibodies that bind immune evasion epitopes — PLoS Pathogens (Hook et al.) , 2026
  5. Immunogenicity and Efficacy of a Trivalent HSV-2 gC2, gD2, gE2 Nucleoside-Modified mRNA-LNP Vaccine Against HSV-1 Eye Infection and Neuroinvasion in Mice — Vaccines (Chalmin Katz et al.) , 2026
  6. Greater Durability and Protection against Herpes Simplex Viral Disease following Immunization of Mice with Single-Cycle ΔgD-2 Compared to an Adjuvanted Glycoprotein D Protein Vaccine — Vaccines (Mahant et al.) , 2023
  7. Glycoprotein G enables HSV-2 neuroinvasion and provides protection as a glycosylated vaccine antigen — PLoS Pathogens (Könighofer et al.) , 2026
  8. ClinicalTrials.gov registry searches for ΔgD-2, deltagD-2 and X-Vax Technology (searched 2026-10-21) — ClinicalTrials.gov , searched 2026-10-21
  9. ClinicalTrials.gov registry searches for EXCT4, Simplexia and glycoprotein G HSV-2 vaccine (searched 2026-10-21) — ClinicalTrials.gov , searched 2026-10-21
  10. Methodology: our sourcing hierarchy — HerpesVaccinations.com , 2026-10-21