RSV Immunization in the United States: A Primer to Help Prepare Patients for the Upcoming Season

Respiratory syncytial virus (RSV) is a common cause of viral upper respiratory tract infection that can lead to pneumonia in some adults and children, particularly infants, the elderly, and immunocompromised patients. RSV “season” in the Northern hemisphere runs from September through February and sometimes into early spring. Fortunately, RSV can be prevented with the recent approval of several new RSV vaccines and monoclonal antibodies for patients at risk for RSV infection. Here, we highlight best practice immunization options and recommendations developed over the past few years as the United States enters a new RSV season.

What are the immunization options to prevent RSV in adults?

Three RSV vaccines are available in the United States. Arexvy (a monovalent vaccine, adjuvanted), Abrysvo (a bivalent vaccine), and MResvia (an mRNA vaccine) are all FDA approved for adults ≥ 60 years old. They are also approved for adults at increased risk for lower respiratory tract infection, with some notable differences: Abrysvo and MResvia are approved for adults aged 18 to 59 years and Arexvy is approved for those aged 50 to 59 years. Abrysvo is the only FDA-approved RSV vaccine for use in pregnant persons, to prevent infections in newborns and infants.

CDC recommendations for RSV immunization in adults currently include a single dose of any RSV vaccine for adults ≥ 75 years old and for adults aged 50 to 74 years who are at an increased risk of severe RSV. Examples of factors that may increase the risk of severe RSV disease include:

Chronic cardiovascular disease
Chronic hematologic conditions
Chronic lung or respiratory disease
Diabetes with chronic kidney disease, neuropathy, retinopathy, end-organ damage, or insulin or sodium-glucose cotransporter-2 (SGLT2) inhibitor treatment
End-stage kidney disease or use of hemodialysis or other renal replacement therapy
Moderate-to-severe immunocompromise, particularly lung transplant and hematopoietic cell (aka bone marrow) transplant patients
Neurologic or neuromuscular condition leading to respiratory weakness or impaired airway clearance
Residence in a nursing home
Severe obesity (body mass index ≥ 40 kg/m^2)
Other chronic conditions or risk factors that may be deemed to predispose to more severe disease with a respiratory infection (such as frailty, concerns for undiagnosed conditions, or living in a remote or rural area where escalation of care may be challenging)

RSV vaccination can be administered at any time but is best given in late summer or early fall, before RSV season is in full swing. As of now, RSV vaccination is a single one-time dose and is not an annual vaccination, like the influenza vaccine.

While Abrysvo and Arexvia are approved for ages younger than the CDC recommendations (adults aged 18-49 years), the CDC has not incorporated this population into vaccine recommendations due to insufficient evidence for effectiveness. Recommendations may be updated as more evidence becomes available on the duration of protection, response after revaccination, immunogenicity in adults with immunocompromise, and cost effectiveness.

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RSV Infection in Adults

What are the immunization options to prevent RSV in pediatric populations?

For the prevention of RSV in infants, the CDC and American Academy of Pediatrics (AAP) recommend either maternal RSV vaccination with Abrysvo or infant immunization with a monoclonal antibody. Available monoclonal antibodies recommended for RSV prophylaxis include nirsevimab and clesrovimab. Nirsevimab and clesrovimab are FDA approved for neonates and infants who were born during or are entering their first RSV season. Nirsevimab is also approved for children ≤ 24 months old who remain vulnerable to severe RSV disease through their second RSV season, such as those with chronic lung disease or hemodynamically significant chronic heart disease. Palivizumab is another humanized monoclonal antibody approved for RSV prevention; however, it is no longer recommended by AAP and will be discontinued as of December 31, 2025.

Vaccination using Abrysvo is recommended from September through January in pregnant people during weeks 32-36 of pregnancy to prevent RSV in the newborn infant. When maternal vaccination is not given (including in cases of unknown vaccination status or if birth was within 14 days of vaccination), administration of nirsevimab or clesrovimab is recommended in infants < eight months old who are born in or entering their first RSV season.

CDC and AAP also recommend nirsevimab for children aged eight-19 months of age who are at increased risk for severe RSV going into their second RSV season. Increased risk is characterized as: (1) having chronic lung disease of prematurity that required medical support such as chronic corticosteroid therapy, diuretic therapy, or oxygen at any time during the six-month period before the start of the second RSV season (2) severe immunosuppression; (3) having cystic fibrosis with either severe lung disease or weight-to-length less than the tenth percentile; or (4) being American Indian or Alaska Native due to the increased incidence reported in these populations.

RSV typically causes mild, cold-like symptoms that resolve in one-two weeks. But for those at increased risk for severe illness, prevention is worth a pound of cure.