FDA Approves mRNA-1345 Vaccine for Adults Aged 18 to 59 Years

The FDA has approved mRNA-1345 (mRESVIA; Moderna, Inc), a respiratory syncytial virus (RSV) vaccine, for the prevention of RSV infection among high-risk individuals aged 18 to 59 years. The expanded indication follows the May 2024 approval for mRNA-1345 to protect adults 60 years and older from lower respiratory tract disease caused by RSV infection.^1-3

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Each year, approximately 60,000 to 160,000 older adults are hospitalized due to RSV, accounting for 6000 to 10,000 deaths. RSV can be especially dangerous for older adults and those with chronic medical conditions who are frail or live in a nursing home.⁴ In adults and older children, the infection presents mild, coldlike symptoms that appear 4 to 6 days after exposure. Symptoms may include a congested or runny nose, dry cough, low-grade fever, sore throat, sneezing, and headache. However, symptoms for severe infection include fever, severe cough, wheezing, rapid breathing or difficulty breathing, and bluish color of the skin, according to the CDC.⁵

"RSV poses a serious health risk to adults with certain chronic conditions, and today's approval marks an important step forward in our ability to protect additional populations from severe illness from RSV," Stéphane Bancel, chief executive officer of Moderna, said in a news release.¹

mRNA-1345’s Role in Protecting Against RSV

mRNA-1345 is an mRNA vaccine designed to protect against RSV. It works by delivering an mRNA sequence that codes for a stabilized prefusion F glycoprotein, which is found on the surface of the RSV virus crucial for cell entry. This prefusion form of the F protein is an effective target for neutralizing antibodies and is consistent across both RSV-A and RSV-B subtypes. Notably, the vaccine utilizes the same lipid nanoparticles as the Moderna COVID-19 delivery, according to the study authors.⁴

Phase 3 Clinical Study Results

The approval of mRNA-1345 is supported by results from a phase 3 study (NCT06067230) that investigated the immunogenicity and safety of the mRNA-1345 vaccine in targeting RSV in high-risk adults. The study was divided into 2 parts: part A, which focused on the safety and immune response to the vaccine in high-risk adults aged 18 to 60 years, and part B, which evaluated the safety and immune response of mRNA-1345 in adults who had received a solid organ transplant.²

Results from the phase 3, placebo-controlled safety and efficacy study demonstrated that the immune responses against RSV-A and RSV-B met noninferiority immunobridging criteria when compared with responses in individuals 60 years and older. Further results displayed comparable levels of neutralizing antibodies across individuals aged 18 to 49 years and individuals aged 50 to 59 years. Overall, mRNA-1345 was well tolerated, with the most common adverse reactions being injection site pain, fatigue, headache, myalgia, and arthralgia.¹

The company intends to have mRNA-1345 available to the eligible populations in the upcoming RSV season in the US.¹

REFERENCES

1. Moderna receives U.S. FDA approval for RSV vaccine, mRESVIA, in adults aged 18–59 at increased risk for RSV disease. Moderna. June 12, 2025. Accessed June 13, 2025. https://investors.modernatx.com/news/news-details/2025/Moderna-Receives-U-S--FDA-Approval-for-RSV-Vaccine-mRESVIA-in-Adults-Aged-1859-at-Increased-Risk-for-RSV-Disease/default.aspx

2. A study to investigate the immunogenicity and safety of mRNA-1345 vaccine targeting respiratory syncytial virus (RSV) in high-risk adults. Clinicaltrials.gov identifier: NCT06067230. Updated November 15, 2024. Accessed June 12, 2025. https://clinicaltrials.gov/study/NCT06067230?rank=1

3. Moderna receives U.S. FDA approval for RSV vaccine mRESVIA(R). Moderna. May 31, 2024. Accessed June 12, 2025. https://investors.modernatx.com/news/news-details/2024/Moderna-Receives-U.S.-FDA-Approval-for-RSV-Vaccine-mRESVIAR/default.aspx

4. CDC. RSV in older adults. August 30, 2024. Accessed June 12, 2025. https://www.cdc.gov/rsv/older-adults/index.html#:~:text=RSV%20can%20be%20dangerous%20for,disease%20get%20an%20RSV%20vaccine.

5. Mayo Clinic. Respiratory syncytial virus (RSV). October 4, 2023. Accessed June 12. 2025. https://www.mayoclinic.org/diseases-conditions/respiratory-syncytial-virus/symptoms-causes/syc-20353098