The US FDA has approved an expanded age indication for Arexvy (respiratory syncytial virus vaccine, adjuvanted), GSK's recombinant protein-based RSV vaccine, extending its use to adults aged 18 to 49 years at increased risk for lower respiratory tract disease caused by RSV. The decision, announced on 13 March 2025, makes Arexvy the third RSV vaccine to receive US FDA approval for at-risk adults under 50, following earlier label expansions for Pfizer's Abrysvo in October 2024 and Moderna's mRESVIA in 2025. Arexvy was previously approved in the US for adults aged 60 and older, and for those aged 50 to 59 at increased risk. An estimated 21 million US adults under 50 have at least one risk factor for severe RSV infection, the company said.
The expanded indication covers adults aged 18 to 49 with chronic conditions that elevate RSV risk, including cardiopulmonary, kidney, and metabolic diseases such as diabetes and obesity. The vaccine is not approved for use in pregnant individuals. Arexvy contains a recombinant RSV glycoprotein F stabilized in the prefusion conformation (RSVPreF3), combined with GSK's proprietary AS01E adjuvant system. It is administered as a single dose. The vaccine is now approved for adults 18 and older in the European Economic Area and across more than 60 countries for various adult age groups.
The FDA's decision was supported by data from a Phase IIIb open-label trial (NCT06389487) enrolling 1,458 participants across 52 sites in six countries. The study evaluated the immune response in 426 at-risk adults aged 18 to 49 compared with 429 adults aged 60 and above after a single dose. Primary endpoints were RSV-A and RSV-B neutralization titres at one month post-vaccination. The trial met its non-inferiority endpoints, demonstrating that the immune response in the younger at-risk cohort was non-inferior to that observed in older adults. Vaccine efficacy against RSV-associated lower respiratory tract disease had been established in the earlier Phase III trial (NCT04886596), which enrolled over 26,000 adults aged 60 and above. The safety profile in the expanded population was consistent with the broader Phase III programme, with injection site pain, fatigue, myalgia, headache, and arthralgia the most commonly reported adverse events.
The approval places Arexvy alongside two other vaccines now available for younger at-risk adults, forming a competitive landscape that includes protein subunit, mRNA, and bivalent approaches. Pfizer's Abrysvo, a non-adjuvanted bivalent prefusion F protein vaccine, received its 18-to-59 expansion in October 2024. Moderna's mRESVIA, the only mRNA-based RSV vaccine, also gained approval for adults 18 to 59 at increased risk in 2025. All three approvals in younger adults relied on immunobridging strategies rather than direct efficacy endpoints in the target population. RSV accounts for approximately 17,000 hospitalisations, 277,000 emergency department visits, and nearly two million outpatient visits annually among US adults aged 18 to 49, with most hospitalisations occurring in those with chronic medical conditions. Prior to these vaccine approvals, no specific prophylactic or therapeutic intervention existed for RSV prevention in this age group. GSK continues to pursue regulatory submissions globally, and the company is conducting additional studies, including a Phase III trial in Chinese adults aged 18 to 59 at increased risk.
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