The FDA has extended approval of GSK's Arexvy vaccine to adults aged 18 to 49 years at higher risk of lower respiratory tract disease (LRTD) caused by RSV.[1][2][3] The vaccine was previously approved to prevent RSV-LRTD in adults 60 years of age and older and in those 50–59 years of age at higher risk.[1][2][3] The expansion affects an estimated 21 million Americans under the age of 50 with at least one risk factor, such as heart failure, coronary heart disease, diabetes, or chronic lung disease.[1][2][4] The approval is based on data from a phase IIIb study (NCT06389487) that showed a comparable immune response to that seen in people over 60 years of age.[2][3] The efficacy of the vaccine was demonstrated in a previous phase III study (NCT04886596).[2] The safety profile is consistent with previous data, with the most common adverse effects including injection site pain, fatigue, muscle, headache, and joint pain within four days of vaccination.[2] Arexvy thus competes with Pfizer's Abrysvo and Moderna's mRESVIA vaccines in the same population.[1]