Vaccine Info

mRNA-1345 Respiratory Syncytial Virus (RSV) Vaccine

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Last reviewed
August 9, 2021
Fact checked by
Robert Carlson, MD

mRNA-1345 Respiratory Syncytial Virus (RSV) Vaccine Description

Moderna Inc.'s mRNA-1345 Respiratory Syncytial Virus (RSV) vaccine candidate encodes for a prefusion F glycoprotein, which elicits a superior neutralizing antibody response. mRNA-1345 uses the same lipid nanoparticle (LNP) as Moderna’s U.S. FDA Authorized SpikeVax Covid-19 vaccine and contains optimized protein and codon sequences.

There is no U.S. FDA-approved vaccine for RSV as of August 3, 2021.

The Phase 1 study of mRNA-1345 to evaluate the tolerability and reactogenicity of mRNA-1345 in younger adults, older adults, and children is ongoing. All four cohorts of younger adults (ages 18-49 years) are fully enrolled. Dosing in the older adult cohort (ages 65-79 years) is ongoing. The age range of toddlers in this de-escalation Phase 1 study is 12-59 months. The Company shared the first interim analysis of the Phase 1 study of mRNA-1345, through 1-month post-vaccination, of the younger adult cohorts at its annual Vaccines Day on April 14, 2021. Results showed the vaccine candidate generated a geometric mean rise in neutralizing antibodies relative to a baseline of at least 11-fold.

“We are pursuing an mRNA RSV vaccine to protect the most vulnerable populations – young children and older adults,” said Stéphane Bancel, CEO of Moderna, in a press statement issued on August 3, 2021. “We are studying mRNA-1345 in these populations in an ongoing clinical trial and we look forward to sharing data when available. The Fast Track designation for older adults underscores the urgent need for a vaccine against RSV. With our investments in science and manufacturing, we have taken eleven infectious disease vaccines into human clinical trials. We have accelerated research and development of our infectious disease therapeutic area and we will continue to advance our mRNA vaccines into new areas of high unmet need.”

Moderna also intends to evaluate the potential of combinations of mRNA-1345 with its vaccines against other respiratory pathogens in children and separately in older adults. Massachusetts-based 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. Today, 24 development programs are underway with 16 programs having entered the clinic. To learn more, visit

mRNA-1345 Respiratory Syncytial Virus (RSV) Vaccine Indication

The mRNA-1345 Respiratory Syncytial Virus (RSV) Vaccine candidate is indicated to prevent illness from the RSV. RSV is the leading cause of respiratory illness in young children. Older adults (65+) are at high risk for severe RSV infections.

RSV is the leading cause of respiratory illness in young children. RSV is the most common cause of bronchiolitis (inflammation of the small airways in the lung) and pneumonia (infection of the lungs) in children younger than 1 year of age. According to the U.S. Centers for Disease Control and Prevention, in the USA, RSV leads each year, on average, to approximately 58,000 hospitalizations among children younger than five years old, 177,000 hospitalizations among adults 65 years and older, and 14,000 deaths among adults 65 years and older.

mRNA-1345 Respiratory Syncytial Virus (RSV) Vaccine News

August 3, 2021 - Moderna, Inc. announced that the U.S. FDA had granted Fast Track designation for mRNA-1345, its investigational single-dose mRNA vaccine against RSV in adults older than 60 years of age.

May 6, 2021 - Moderna Inc., investor presentation regarding mRNA-1345 vaccine candidate.

April 14, 2021 - Moderna shared the first interim analysis of the Phase 1 study after 1-month post-vaccination of younger adults (18-49). 'mRNA-1345 was shown to increase RSV neutralizing antibodies in seropositive younger adults. Neutralizing antibodies were confirmed to be present at baseline in all participants, as expected. A single vaccination of mRNA-1345 at the 50 or 100 μg dose level boosted neutralizing antibody titers against both serotypes of RSV-A and RSV-B with no apparent dose-response. At month 1, the geometric mean fold rise in neutralizing antibody relative to baseline was at least 20.5 for RSV-A and at least 11.7 for RSV-B.'

mRNA-1345 Respiratory Syncytial Virus (RSV) Vaccine Clinical Trials

Clinical Trial NCT04528719: A Dose Escalation Study to Evaluate Safety, Reactogenicity, and Immunogenicity of mRNA-1345 in Healthy Adults and in Children Who Are Respiratory Syncytial Virus Seropositive. Estimated Completion Date: September 30, 2023