Immunization Updates from Moderna, Merck

Moderna Wins FDA Approval for its Influenza Vaccine

Yesterday, the vaccine manufacturer announced the FDA approved mRNA-1010 (mFLUSIVA) a new mRNA-based vaccine for seasonal influenza, for use in adults 50 and older. The approval marks Moderna's fourth FDA-approved product and its fifth approved product worldwide.¹ The decision follows a unanimous recommendation from the FDA's Vaccines and Related Biological Products Advisory Committee in support of mRNA-1010 for this age group.¹

For adults 50 through 64, the approval is based on a large phase 3 trial that enrolled more than 40,800 adults across 11 countries, comparing mRNA-1010's safety and relative efficacy against a standard-dose flu vaccine. For adults 65 and older, the FDA granted accelerated approval based on a separate trial of nearly 3000 US participants that measured immune response against a high-dose comparator vaccine; further confirmation of clinical benefit in this older group will come from a postmarketing study. Across the program, Moderna reported an acceptable safety profile with no new safety concerns.¹

Moderna's Chief Executive Officer Stéphane Bancel, called the approval a sign of his company's staying power in the vaccine space. "The FDA approval of mFLUSIVA... demonstrates the continued strength and versatility of our mRNA platform," he said, adding that the vaccine "provides an important new option for America's seniors."¹

Moderna said it expects mRNA-1010 to reach select US retailers within weeks, positioning it alongside the company's existing respiratory vaccine lineup — Spikevax, mRESVIA and mNEXSPIKE — in time for the 2026-2027 respiratory virus season. The vaccine is also under regulatory review in the European Union, Canada and Australia, with additional submissions planned later this year.¹

FDA, EMA Accept Applications to Expand Enflonsia’s RSV Protection to a Second Season

Merck announced today that the FDA has accepted a supplemental Biologics License Application for clesrovimab-cfor (ENFLONSIA) seeking to expand the drug's approval to cover children under two years old who face an increased risk of severe respiratory syncytial virus (RSV) disease during their second RSV season. The FDA has set a target action date of March 22, 2027, under the Prescription Drug User Fee Act.²

The European Medicines Agency accepted a similar application for the same population in July 2026.²

Clesrovimab-cfor is currently approved in the US and more than 40 other countries — including Canada, the European Union, China and Japan — to protect infants during their first RSV season. The FDA approved it in June 2025, and the European Commission followed in April 2026. Merck notes it remains the only RSV prevention option for infants that doesn't require weight-based dosing.²

The push to extend protection into a second season addresses a gap for particularly vulnerable children. Even after receiving protection in their first RSV season, some children—including those born with chronic lung disease, congenital heart disease, or early to moderate preterm birth with certain risk factors — remain susceptible to severe RSV illness the following year.²

Macaya Douoguih, MD, MPH, vice president and therapeutic area head for Global Clinical Development at Merck Research Laboratories, framed the filings as a way to close that gap. "For some children, the potentially serious impact of RSV does not stop after their first RSV season," she said, adding that the new filings "represent important opportunities to help expand protection with ENFLONSIA for vulnerable children under two years of age during their second RSV season."²

Both the US and EU applications draw on data from the phase 3 SMART trial (MK-1654-007), a randomized, partially blind, palivizumab-controlled study that tracked infants and children at heightened RSV risk over two seasons. In the first season, 502 participants received a 105 mg dose of clesrovimab-cfor and 501 received monthly palivizumab. In the second season, 276 eligible children— those with chronic lung disease, congenital heart disease, or qualifying preterm birth—received an additional 210 mg open-label dose of clesrovimab-cfor. Trial results were presented at the RSVVW'26 conference in February 2026 and published in the New England Journal of Medicine in September 2025 and in JAMA Pediatrics in July 2026.²

Merck said regulatory filings for clesrovimab-cfor are underway in additional countries, both for initial approval and for expanding existing indications.²

References
1.Moderna Receives U.S. FDA Approval for Influenza Vaccine mFLUSIVA. Moderna press release. August 5, 2026. Accessed August 6, 2026.
https://feeds.issuerdirect.com/news-release.html?newsid=4801915282452025&symbol=MRNA

2. U.S. FDA Accepts sBLA for ENFLONSIA™ (clesrovimab-cfor) to Update its Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease Indication to Include Children Under Two Years at Increased Risk for Severe RSV for Their Second Season. Merck press release. August 6, 2026. Accessed August 6, 2026.https://www.merck.com/news/u-s-fda-accepts-sbla-for-enflonsia-clesrovimab-cfor-to-update-its-respiratory-syncytial-virus-rsv-lower-respiratory-tract-disease-indication-to-include-children-under-two-years-at-increa/