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Moderna Announces First Participant Dosed in Phase 2/3 Study of its mRNA Respiratory Syncytial Virus (RSV) Vaccine

Moderna expects to enroll approximately 34,000 participants in multiple countries

RSV is a leading cause of severe respiratory illness in older adults (65+) and young children; there is no approved vaccine to prevent RSV

RSV illness in older adults results in an estimated $3 billion in annual medical costs in the U.S. each year

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 2/3 study of mRNA-1345, the Company’s Respiratory Syncytial Virus (RSV) vaccine candidate. This study is known as ConquerRSV.

“RSV is a respiratory virus that can result in hospitalization and death in adults over 65 years of age. Yet, RSV illness in older adults is often under-recognized and there is no vaccine against it. The start of this international Phase 2/3 study is an important milestone as we continue to advance mRNA vaccines against respiratory viruses,” said Stéphane Bancel, Moderna’s Chief Executive Officer. “We believe that vaccine candidate against RSV can have a positive impact on public health as RSV represents a significant unmet global need. In addition, we believe that combination vaccines against multiple respiratory pathogens can help ensure that people are fully vaccinated by leading to higher compliance and better uptake, which may result in a longer-term benefit to health care systems and protect people from a broader number of respiratory viruses.”

RSV is a common respiratory virus that generally causes cold-like symptoms. In the U.S. and areas with similar climates, RSV infections occur primarily during fall, winter, and spring. Most people recover in approximately one to two weeks, but RSV can be serious, especially for young children under 5 years of age and older adults over 65 years of age. RSV is a leading cause of severe respiratory illness in older adults and young children. In older adults, RSV can result in pneumonia and respiratory distress and represents a substantial burden of illness. In the U.S., RSV causes approximately 177,000 hospitalizations and 14,000 deaths in adults 65 years and older. Additionally, RSV in older adults results in an estimated $3 billion in annual medical costs in the U.S. each year. RSV is also the most common cause of bronchiolitis and pneumonia in children younger than one year of age in the U.S. RSV leads each year, on average, to approximately 58,000 hospitalizations among children younger than five years. There is no approved vaccine available today for RSV.

Moderna’s mRNA vaccine portfolio includes candidates against respiratory viruses, candidates against tropical viruses, and candidates against latent viruses. In Moderna’s respiratory virus vaccine program, in addition to its RSV vaccine candidate, the Company is advancing COVID-19 booster vaccine candidates and a seasonal flu vaccine candidate (mRNA-1010). At Moderna’s annual R&D Day in September, the Company announced that it is developing a single dose vaccine that combines a booster against COVID-19 and a booster against flu. The Company is also advancing a combination vaccine candidate against human metapneumovirus and parainfluenza virus 3 (hMPV/PIV3) and a combination vaccine candidate against both pediatric RSV and hMPV. In preclinical studies, Moderna has observed that its seasonal flu, RSV and COVID-19 booster vaccines can be combined into one dose that produces an immune response to all six antigens1. Moderna intends to explore vaccine combinations including RSV, Flu and COVID-19.

mRNA-1345 is a vaccine against RSV encoding for a prefusion F glycoprotein, which elicits a superior neutralizing antibody response compared to the postfusion state. mRNA-1345 uses the same lipid nanoparticle (LNP) as Moderna’s COVID-19 vaccine and contains optimized protein and codon sequences. The FDA has granted Fast Track designation for mRNA-1345 in adults older than 60 years of age.

The Company recently shared interim data Phase 1 study of mRNA-1345 in older adults ages 65-79 years. Neutralizing antibodies were confirmed to be present at baseline in all participants, as expected. The data showed that a single mRNA-1345 vaccination of 50 µg, 100 µg or 200 µg boosted neutralizing antibody titers against RSV-A by approximately 14-fold and against RSV-B by approximately 10-fold. Data were pooled across dose levels because there was not a significant difference between doses. A single vaccination of 50 µg, 100 µg or 200 µg was well-tolerated in older adults through month one.

The Phase 2/3, randomized, observer-blind, placebo-controlled, multicenter study will be conducted in multiple countries. Moderna is choosing study locations based on the ongoing epidemiology of RSV. The study is known as ConquerRSV. The primary purpose of the Phase 2 segment of the study is to evaluate the safety of mRNA-1345 vaccine in adults older than 60 years of age for initiation of the large‑scale Phase 3 segment of the study. The primary purpose of the Phase 3 segment of the study is to establish the safety and efficacy of mRNA-1345 vaccine in adults older than 60 years of age in support of licensure. Moderna expects to enroll approximately 34,000 participants. To learn more about eligibility, please click here.

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 seven 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 development of a vaccine candidate against respiratory syncytial virus (RSV) (mRNA-1345); the ability of mRNA-1345 to induce neutralizing antibodies against RSV in older adults; the safety profile and tolerability of mRNA-1345; the ability of mRNA-1345 to reduce RSV infections in older adults; the conduct of Phase 2/3 clinical trials for mRNA-1345; the potential for the Company to produce and commercialize combination vaccines; the disease burden and costs associated with RSV infection; and the Company’s development of vaccine candidates against other respiratory diseases, including seasonal flu and COVID-19. 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.



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