Vaccine Info

mRNA-1608 Herpes Vaccine

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Last reviewed
May 3, 2024
Fact checked by
Robert Carlson, MD

mRNA-1608 Herpes Vaccine Candidate Clinical Trials, Dosage, Indication, News, Side Effects

Moderna Inc.'s herpes simplex virus (HSV) vaccine candidate (mRNA-1608) is a Messenger RNA (mRNA) vaccine targeted against HSV-2 disease. On February 18, 2022, Moderna Inc. stated that it expects an HSV-2 vaccine could provide cross-protection against HSV-1. With mRNA-1608, Moderna aims to induce a strong antibody response with neutralizing and effector functionality combined with cell-mediated immunity. A prophylactic genital herpes vaccine should prevent HSV-1 and HSV-2 genital lesions and infection of the dorsal root ganglia, the site of latency. In addition, vaccine immunity should be durable for decades, perhaps with booster doses. While these goals have been elusive, new efforts with nucleoside-modified mRNA-lipid nanoparticle vaccines show great promise. 

Moderna is developing mRNA-1608 to reduce the burden of HSV lesions based on mRNA technology that offers potential advantages in efficacy, speed of development, and production scalability and reliability, which may position our company as a leader in preparing for and responding to infectious disease threats that place millions of people at risk worldwide. To further characterize Moderna's IM vaccines, biodistribution studies were conducted to demonstrate where mRNA goes in the body after injection. Studies indicate that injected mRNA remains predominantly at the injection site and nearby draining lymph nodes. Furthermore, consistent with its transient nature, mRNA is undetectable in the body five days after injection, with minimal mRNA detectable after only three days.

A Phase 1 clinical study of mRNA-1608 in Healthy Adults 18 to 55 with Recurrent HSV-2 Genital Herpes began recruiting participants on September 6, 2023. On March 27, 2024, Moderna confirmed the first-in-human, fully enrolled Phase 1/2 clinical trial (NCT06033261) of mRNA-1608, which includes three hundred participants with a history of recurrent genital herpes, randomly assigned in a 1:1:1:1 ratio to receive mRNA-1608 at one of the three dose levels or control (BEXSERO) administered as two doses at 0 and 2 months (Day 1 and Day 57). This study (mRNA-1608-P101) aims to generate safety and immunogenicity data and establish a proof-of-concept of the clinical benefit of the mRNA-1608 vaccine candidate. On May 2, 2024, Moderna announced the Phase 1/2 study of mRNA-1608 was fully enrolled. The actual study Start Date was September 6, 2023, and the Estimated Primary Completion Date is June 4, 2025.

As of May 2024, there is no herpes vaccine approved by the U.S. Food and Drug Administration (FDA).

Massachusetts-based Moderna, Inc. (NASDAQ: MRNA) is a biotechnology company pioneering messenger RNA therapeutics and vaccines. Moderna now has vaccine candidates against latent viruses in development, including cytomegalovirus, Epstein-Barr virus, Human immunodeficiency virus, HSV, and VZV.

mRNA-1608 Indication

In the U.S., approximately 18.6 million adults ages 18 to 49 live with HSV-2. The U.S. CDC says herpes simplex viruses are categorized into two types: HSV-1 infects the mouth, face, and genitals, and HSV-2 primarily infects the genitals. Both herpes viruses establish lifelong latent infections within sensory neurons from which they can reactivate and re-infect the skin.

Herpes Testing 2023

The JAMA Network published on February 14, 2023, the US Preventive Services Task Force recommends against routine serologic screening for genital HSV infection in asymptomatic people. However, herpes tests can be ordered online at

mRNA-1608 Herpes Vaccine Candidate News

March 27, 2024 - Stéphane Bancel, Chief Executive Officer of Moderna, commented in a press release, "With five vaccines in Phase 3, and three more moving toward Phase 3, we have an extensively large and diverse portfolio addressing significant unmet medical needs. We are focused on execution to further build momentum across our pipeline and business deliver for patients impacted by these infectious diseases."

May 24, 2022 - Digital Journal reported: Here At Meet Positives, we are very grateful for Moderna's mRNA's progress. Wecine and can't wait for it to positively affect the lives of the millions of citizens living today under the fear of contracting herpes."

May 4, 2022 - Moderna confirmed preclinical studies are underway for the mRNA-1608 vaccine candidate.

April 2022 - NIH published a study that discusses the trivalent mRNA-lipid nanoparticle approach for a prophylactic genital herpes vaccine and the ability of the vaccine to induce higher titers of neutralizing antibodies and more durable CD4+ T follicular helper cell and memory B cell responses than protein-adjuvanted vaccines.

March — 2022 - Moderna Inc. confirmed preclinical studies are underway for VZV (mRNA-1468) and HSV (mRNA-1608) vaccine candidates, both members of the Herpesviridae family that establish life-long latent infections.

February 18, 2022 - Moderna, Inc. announced an expansion of its mRNA vaccine pipeline with three new development programs. "We are pleased to announce these new development programs, which reflect the continued productivity of our platform and the potential of our mRNA technology to impact the lives of hundreds of millions of people," said Stéphane Bancel, Chief Executive Officer of Moderna. 

December 22, 2021 - Translational Research published a Review article: An mRNA vaccine to prevent genital herpes. 

July 27, 2020 - PLOS published a study that concluded: We consider the HSV-2 trivalent mRNA vaccine a promising candidate for clinical trials to prevent HSV-1 and HSV-2 genital herpes.

mRNA-1608 Herpes Vaccine Candidate Clinical Trials

As of March 2024, Moderna publishes clinical trial updates at this weblink.

A Phase 1/2, Randomized, Observer-Blind, Controlled, Dose-Ranging Study of mRNA-1608, an HSV-2 Therapeutic Candidate Vaccine, in Healthy Adults 18 to 55 Years of Age With Recurrent HSV-2 Genit—Last updated update March 5, 2024. This study aims to generate safety and immunogenicity data and establish a proof-of-concept of the clinical benefit of the mRNA-1608 vaccine candidate.

Clinical Trials

No clinical trials found