State of the evidence: October 2026
Published:
A plain-language look at where herpes vaccine research stood at the end of October 2026. No tracked trial changed status this month. The two registered trials still running, for BNT163 and for an HSV-2 mRNA vaccine from Changchun BCHT, are both phase 1, small first safety tests in people. Four vaccines or vaccine approaches that have only been tested in animals 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.
First published 21 October 2026. Updated 2 November 2026 to cover the rest of October: two more animal-only vaccines were added, the BNT163 entries now reflect the registry’s 22 October 2026 edit and the passing of its October estimate, and a few older lines were corrected.
What changed this month
- No tracked trial changed status. Each week 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. Two records had only their “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.
- Later in the month we added two more. The Prime/Pull/Keep approach from the University of California, Irvine has been tested in guinea pigs (HSV-2) and rabbits (HSV-1). M6 is a weakened HSV-1 virus made at the Institute of Medical Biology in Kunming, China. It has been tested in mice and in rhesus macaques (a kind of monkey), and only against HSV-1. 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 only early results have been shared. 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 has protected mice in studies. 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 first two 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.
- Prime/Pull/Keep is meant to treat, not prevent. It is a “therapeutic” approach: it is given after infection, to reduce outbreaks. It has three steps. The first teaches T cells (immune cells that kill infected cells) to spot HSV. The second draws them to the places where the virus hides. The third helps them stay there. Studies report fewer repeat outbreaks in guinea pigs already infected with HSV-2, and less eye disease in rabbits already infected with HSV-1. The vaccine parts differ from study to study, so this is an approach rather than one fixed vaccine. There are no results in people.
- M6 has animal results for HSV-1 only. M6 is “live-attenuated”: the virus is weakened but can still multiply. In a 2020 study, mice and rhesus macaques given M6 had no disease signs after being given HSV-1, and lower levels of viral DNA than unvaccinated animals. The groups were small. The study did not test HSV-2, and there are no results in people.
What we still don’t know
- Whether any herpes vaccine prevents or treats herpes in people. The largest tracked trial, of GSK’s Herpevac (phase 3, a large late-stage test in about 8,300 women), reported in 2012. It did not prevent genital disease caused by HSV-2, its target. It unexpectedly reduced genital disease caused by HSV-1, by about 58%, but the program was not taken further. No tracked vaccine in a running trial has results that test whether it prevents or treats herpes.
- Whether BNT163’s trial has finished. Its registry record was last edited on 22 October 2026. It still estimated that the trial would finish in October 2026, and it still said the trial was active. As of 2 November the record had not changed. We could not check BioNTech’s own announcements 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 four new animal-only vaccines have any plan for human testing. We found no primary source saying so for any of them.
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. That month has now passed. The record (last updated 22 October 2026) still lists the trial as active, and no results are posted. A passed estimate does not tell us how the trial went. Even when a trial finishes, results may not be published for some time. We will report when the record changes.
- BCHT HSV-2 mRNA vaccine trial: registry estimates of 4 March 2027 for primary completion and June 2027 for overall completion. This phase 1 trial is enrolling by invitation. The record was last updated on 9 January 2026, so its dates may be out of date. These are registry estimates, not promises.
Nothing else we track has a date on a public record.
Every source for this update is listed below. If you spot an error, see the About page for how to tell us.
Sources
- 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)
- 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)
- Safety and Immunogenicity of BNT163, a Trivalent mRNA HSV Vaccine Candidate for Genital Herpes (abstract P-105)
- HSV-2 gC2 mRNA immunization in mice protects by producing antibodies that bind immune evasion epitopes
- 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
- 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
- Glycoprotein G enables HSV-2 neuroinvasion and provides protection as a glycosylated vaccine antigen
- A Phase I, Dose-escalation Study to Evaluate the Safety, Tolerability, and Immunogenicity of an mRNA Vaccine Against Herpes Simplex Virus Type 2 (HSV-2) in Healthy Participants Aged 18-55 Years, Stratified by Serostatus (NCT07330440)
- Phase III Study to Assess the Prophylactic Efficacy and Safety of gD-Alum/MPL Vaccine in Young Women Seronegative for HSV-1 and HSV-2 (NCT00057330)
- Efficacy Results of a Trial of a Herpes Simplex Vaccine (Belshe et al.)
- Therapeutic prime/pull vaccination of HSV-2-infected guinea pigs with the ribonucleotide reductase 2 (RR2) protein and CXCL11 chemokine boosts antiviral local tissue-resident and effector memory CD4+ and CD8+ T cells and protects against recurrent genital herpes
- A tissue-targeted prime/pull/keep therapeutic herpes simplex virus vaccine protects against recurrent ocular herpes infection and disease in HLA-A*0201 transgenic rabbits
- ClinicalTrials.gov registry searches for BenMohamed, prime pull keep herpes and rAd-RR2 (searched 2026-10-22)
- A HSV1 mutant leads to an attenuated phenotype and induces immunity with a protective effect
- ClinicalTrials.gov registry searches for attenuated HSV-1, M6 herpes, Institute of Medical Biology herpes, Qihan Li and Kunming (searched 2026-10-26)
- ClinicalTrials.gov registry searches for ΔgD-2, deltagD-2 and X-Vax Technology (searched 2026-10-21)
- ClinicalTrials.gov registry searches for EXCT4, Simplexia and glycoprotein G HSV-2 vaccine (searched 2026-10-21)
- Methodology: our sourcing hierarchy
Each quarter: our Frontier Analysis looks across the whole record for patterns and AI-written questions. It is analysis, not news, and is checked by a Critic AI.