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Moderna Announces First Participant Dosed in Phase 3 Pivotal Registration Study of Its mRNA Cytomegalovirus (CMV) Vaccine

CMV is the most common infectious cause of birth defects in the U.S.; there is no approved vaccine to prevent CMV

CMV is a latent virus that remains in the body for life after infection and can lead to lifelong medical conditions

mRNA-1647 combines six mRNAs in one vaccine, which encode for proteins for the prevention of CMV infection

Moderna, Inc. (Nasdaq: MRNA), a biotechnology company pioneering messenger RNA (mRNA) therapeutics and vaccines, today announced the first participant has been dosed in the Phase 3 pivotal registration study of mRNA-1647, the Company’s cytomegalovirus (CMV) vaccine candidate. This study is known as CMVictory.

“CMV is a complex, latent virus and represents a significant unmet medical need. The CDC estimates that 1 in 200 babies are born with CMV, and approximately 1 in 5 of them will have devastating sequelae such as hearing loss, seizures, and blindness. We believe that our mRNA vaccine technology is well-suited to provide protection against this latent virus,” said Stéphane Bancel, Moderna’s Chief Executive Officer. “The start of the second Phase 3 study in our company’s history is an exciting milestone for Moderna and I would like to thank the Moderna team as well as our partners at clinical trial sites. This study will allow us to get closer to our goal of addressing this unmet need with a preventative mRNA vaccine against primary CMV infection.”

CMV is a latent virus that remains in the body for life after infection. In adults, initial infection with CMV often goes undetected. The CDC estimates that over half of adults are infected by age 40. For most healthy individuals, CMV does not pose a long-term health risk, but it can lead to lifelong medical conditions. For some, including those with weakened immune systems or infants born with CMV infection, it can have serious consequences. A pregnant mother with an active CMV infection may pass the virus to her unborn child, resulting in congenital CMV infection. Although most infants with congenital CMV appear normal at birth, approximately 1 in 5 will have long-term health problems such as hearing loss, vision impairment, learning disabilities and decreased muscle strength and coordination.1,2 Some newborns with congenital CMV appear very ill at birth with jaundice, rash, liver and spleen enlargement, and seizures. Congenital CMV is the leading infectious cause of birth defects in the United States.3

Moderna’s mRNA vaccine portfolio includes candidates against respiratory viruses, candidates against tropical viruses, and candidates against latent viruses. Latent viruses remain in the body for life after infection. mRNA-1647 is the Company’s first attempt to help protect people from latent virus infection with a vaccine. Moderna is also advancing vaccine candidates against other latent viruses including Epsten-Barr virus (EBV) and human immunodeficiency virus (HIV). EBV is a member of the herpesvirus family that includes CMV, herpes simplex virus (HSV), and varicella-zoster virus (VZV). EBV is spread through bodily fluids (e.g., saliva) and contracted primarily by young children and adolescents. It is a major cause of infectious mononucleosis (IM) and associated risks to other long-term medical conditions including an increased risk of developing multiple sclerosis by approximately 4 to 10-fold, certain lymphoproliferative disorders and cancers and autoimmune diseases4,5. HIV is the virus responsible for acquired immunodeficiency syndrome (AIDS), a lifelong, progressive illness with no effective cure. Worldwide, approximately 38 million are currently living with HIV6 ; including approximately 1.2 million in the U.S.7 Approximately 2 million new infections are acquired worldwide each year, and approximately 690,000 of those people die.

Moderna’s vaccine candidate against CMV, mRNA-1647, combines six mRNAs in one vaccine, which encode for two proteins located on the surface of CMV: five mRNAs encoding the subunits that form the membrane-bound pentamer complex and one mRNA encoding the full-length membrane-bound glycoprotein B (gB). Both the pentamer and gB are essential for CMV to infect barrier epithelial surfaces and gain access to the body, which is the first step in CMV infection. mRNA-1647 is designed to produce an immune response against both the pentamer and gB for the prevention of CMV infection. Currently, there is no approved vaccine to prevent CMV.

Phase 1 and 2 studies of mRNA-1647 demonstrated functional antigen-specific responses that support the vaccine candidate’s potential to prevent CMV infection. Interim, seven-month data from the Phase 2 study of mRNA-1647 at the 50 μg, 100 μg and 150 μg dose levels showed that mRNA-1647 was generally well tolerated. Based on the interim analysis of the Phase 2 study, the 100 μg dose was chosen for the Phase 3 study.

The Phase 3 study, known as CMVictory, will evaluate the safety and efficacy of mRNA-1647 against primary CMV infection in women ages 16-40 years. The Company will seek to enroll approximately 8,000 participants in the study, including 6,900 women of childbearing age, from approximately 150 sites globally, beginning in the U.S. Moderna has set a goal of enrolling a diverse group of U.S. participants into the study, including approximately 42% of participants who are Persons of Color. The identifier is NCT05085366. To learn more about eligibility, please click here.

To find additional information on CMV, please visit Moderna’s resource page,

About Moderna

In 10 years since its inception, Moderna has transformed from a science research-stage company advancing programs in the field of messenger RNA (mRNA), to an enterprise with a diverse clinical portfolio of vaccines and therapeutics across six modalities, a broad intellectual property portfolio in areas including mRNA and lipid nanoparticle formulation, and an integrated manufacturing plant that allows for both clinical and commercial production at scale and at unprecedented speed. Moderna maintains alliances with a broad range of domestic and overseas government and commercial collaborators, which has allowed for the pursuit of both groundbreaking science and rapid scaling of manufacturing. Most recently, Moderna’s capabilities have come together to allow the authorized use of one of the earliest and most-effective vaccines against the COVID-19 pandemic.

Moderna’s mRNA platform builds on continuous advances in basic and applied mRNA science, delivery technology and manufacturing, and has allowed the development of therapeutics and vaccines for infectious diseases, immuno-oncology, rare diseases, cardiovascular diseases and autoimmune diseases. Moderna has been named a top biopharmaceutical employer by Science for the past six years. To learn more, visit

Forward Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including regarding: the Company’s efforts to develop a vaccine against cytomegalovirus, or CMV (mRNA-1647); and the conduct of the Phase 3 clinical study of mRNA-1647. The forward-looking statements in this press release are neither promises nor guarantees, and you should not place undue reliance on these forward-looking statements because they involve known and unknown risks, uncertainties, and other factors, many of which are beyond Moderna’s control and which could cause actual results to differ materially from those expressed or implied by these forward-looking statements. These risks, uncertainties, and other factors include those other risks and uncertainties described under the heading “Risk Factors” in Moderna’s most recent Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission (SEC) and in subsequent filings made by Moderna with the SEC, which are available on the SEC’s website at Except as required by law, Moderna disclaims any intention or responsibility for updating or revising any forward-looking statements contained in this press release in the event of new information, future developments or otherwise. These forward-looking statements are based on Moderna’s current expectations and speak only as of the date hereof.




4 Saade A et al, Infect Dis Now (2021),

5 Jacobs M et al, Mult Scler. (2020),

6 HIV Global Statistics.

7 Centers for Disease Control and Prevention. HIV Surveillance Report, 2018 (Updated); vol.31. Published May 2020


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