No widely available, highly effective vaccine for herpes simplex virus (HSV) is currently on the market. Significant scientific efforts are underway to develop both preventative and therapeutic options.
Current State of Herpes Vaccine Research
Herpes vaccine development is a global endeavor, with multiple candidates progressing through various stages of research. Many potential vaccines are in preclinical studies, while others have advanced to human clinical trials, including Phase 1, Phase 2, and Phase 3. Organizations like the World Health Organization (WHO) and the U.S. National Institutes of Health (NIH) support these developments.
Notable candidates include Moderna’s mRNA-1608, an mRNA vaccine for HSV-2 disease currently in a Phase 1/2 clinical trial, which began in September 2023 and is expected to conclude in June 2025. BioNTech is also testing an mRNA-based HSV prevention vaccine, BNT163, in a Phase 1 study anticipated to finish by December 2025. Additionally, Assembly Biosciences has a helicase primase inhibitor, ABI-5366, in Phase 1a/1b trials targeting recurrent genital herpes.
Different Vaccine Strategies
Herpes vaccine development generally pursues two main objectives: preventative and therapeutic. Preventative vaccines aim to stop infection in individuals who have not yet been exposed to the virus. Therapeutic vaccines, conversely, are designed for those already infected, seeking to reduce the frequency and severity of outbreaks, as well as decrease viral shedding and transmission. Some candidates are being explored for potential dual use.
Various scientific approaches are being employed. Subunit vaccines, for instance, use specific viral proteins to stimulate an immune response. mRNA vaccines, a newer technology, deliver genetic instructions to human cells, enabling them to produce viral proteins that then trigger immunity. Other strategies include live attenuated vaccines, which use a weakened form of the virus, and viral vector vaccines, which employ a harmless virus to deliver herpes genetic material.
Major Obstacles to Development
Developing an effective herpes vaccine faces significant biological and immunological challenges. A primary hurdle is the virus’s ability to establish latency, meaning it can hide dormant within nerve cells for extended periods, effectively evading the immune system. This latent state makes it difficult for the body’s immune defenses, or a vaccine, to completely eliminate the virus.
The herpes virus also possesses sophisticated mechanisms for immune evasion, further complicating vaccine efforts. Inducing a robust and long-lasting immune response against a virus that can hide and adapt is complex. Effective vaccines need to stimulate strong T-cell responses and potentially mucosal immunity to counter both initial infection and subsequent viral reactivation. The interplay between the virus and the host’s immune system presents a barrier to developing a broadly protective vaccine.
What to Expect Regarding Availability
Bringing any vaccine to widespread availability is a lengthy and highly regulated process. Even with promising candidates, they must successfully navigate multiple phases of clinical trials to demonstrate both safety and effectiveness. Following successful trials, regulatory bodies, such as the U.S. Food and Drug Administration (FDA), must approve the vaccine. Manufacturing at a large scale further extends the timeline before a vaccine can be widely distributed. Even with strong trial results, widespread public access typically takes many years.
It is possible that initial vaccines might offer incremental progress, such as reducing the severity of outbreaks or lowering transmission rates, rather than providing complete prevention of infection. This phased improvement could precede the development of a more comprehensive vaccine. While progress is being made, patients should anticipate a realistic timeline, possibly several years, before a herpes vaccine is widely available.