Clinical Overview of RSV

A new RSV vaccine is recommended for pregnant people who are 32–36 weeks pregnant with seasonal administration during September–January in most of the continental United States. In jurisdictions with seasonality that differs from most of the continental United States (e.g., Alaska, jurisdictions with tropical climates), providers should follow state, local, or territorial guidance on timing of administration.

This vaccine provides protection against severe RSV illness to the recipient's baby for up to 6 months of age. However, the infant's protection will wane over time.

Healthcare providers of pregnant people should provide information on maternal vaccines and infant monoclonal antibody products and consider patient preferences when determining whether to vaccinate the pregnant patient or to not vaccinate and rely on administration of nirsevimab to the infant after birth.

Nirsevimab (Beyfortus) is a monoclonal antibody product that can protect infants and some young children from severe RSV disease. It is recommended for:

• Infants under 8 months old born during – or entering – their first RSV season (typically fall through spring) if their mother did not receive an RSV vaccine, it is unknown whether their mother received an RSV vaccine, or the mother received a vaccine but the infant was born <14 days after vaccination
• Some children between the ages of 8 and 19 months who are at increased risk of severe RSV disease before their second RSV season. These include:
  • Children who have chronic lung disease of prematurity who required medical support (chronic corticosteroid therapy, diuretic therapy, or supplemental oxygen) any time during the 6-month period before the start of the second RSV season
  • Children with severe immunocompromise
  • Children with cystic fibrosis who have severe disease
  • American Indian and Alaska Native children

Nirsevimab can be considered in rare circumstances even though the mother received an RSV vaccine when, per the clinical judgment of the healthcare provider, the potential incremental benefit of administration is warranted:

• Pregnant people who may not mount an adequate immune response to vaccination (e.g., people with immunocompromising conditions) or have conditions associated with reduced transplacental antibody transfer (e.g., people living with HIV)
• Infants who have had cardiopulmonary bypass leading to loss of RSV antibodies
• Infants with substantially increased risk for severe RSV disease (e.g., hemodynamically significant congenital heart disease, intensive care admission, and requiring oxygen at discharge)

Nirsevimab is administered by intramuscular injection. It is long-acting, providing protection for at least 5 months (the average length of one season), and only one dose is recommended for an RSV season. However, immune protection will wane over time. Another monoclonal antibody, Palivizumab (Synagis), is recommended by the American Academy of Pediatrics (AAP) for administration to infants and young children who are at increased risk of severe RSV disease based on gestational age and certain underlying medical conditions. It is given in monthly intramuscular injections during RSV season. AAP has provided considerations for the 2023–2024 RSV season with regard to palivizumab versus nirsevimab administration for high-risk infants during the same RSV season.

RSV infection can cause a variety of respiratory illnesses and symptoms in infants and young children. It most commonly causes a cold-like illness but can also cause lower respiratory infections like bronchiolitis and pneumonia. Two to three percent of infants with RSV infection may need to be hospitalized. Severe disease most commonly occurs in very young infants. Additionally, children with any of the following underlying conditions are considered at increased risk:

• Premature infants
• Infants, especially those 6 months and younger
• Children younger than 2 years old with chronic lung disease or congenital heart disease
• Children with suppressed or weakened immune systems
• Children who have neuromuscular disorders or a congenital anomaly, including those who have difficulty swallowing or clearing mucus secretions
• Children with severe cystic fibrosis

Infants and young children with RSV infection may have rhinorrhea and a decrease in appetite before any other symptoms appear. Cough usually develops 1 to 3 days later. Soon after the cough develops, sneezing, fever, and wheezing may occur. Symptoms in very young infants can include irritability, decreased activity, and apnea.

Most otherwise healthy infants and young children who are infected with RSV do not need hospitalization. Those who are hospitalized may require oxygen, rehydration, and mechanical ventilation. Most improve with supportive care and are discharged in a few days.

Adults who get an RSV infection usually have mild or no symptoms. Symptoms are usually consistent with an upper respiratory tract infection, which can include rhinorrhea, pharyngitis, cough, headache, fatigue, and fever. Disease usually lasts less than 5 days.

Some adults, however, may have more severe symptoms consistent with a lower respiratory tract infection, such as pneumonia. Epidemiologic evidence indicates that people 60 and older who are at highest risk of severe RSV disease include those with any of the following chronic conditions:

• Lung disease (such as chronic obstructive pulmonary disease [COPD] and asthma)
• Chronic cardiovascular diseases (such as congestive heart failure and coronary artery disease)
• Diabetes mellitus
• Neurologic conditions
• Kidney disorders
• Liver disorders
• Hematologic disorders
• Immune compromise
• Other underlying conditions that a healthcare provider determines might increase the risk for severe respiratory disease

Other underlying factors that the provider determines might increase the risk of severe RSV-associated respiratory illness may include the following:

• Frailty
• Advanced age*
• Residence in a nursing home or other long-term care facility
• Other underlying factors

*The risk of severe RSV among adults increases with age, with the highest rates of hospitalization among those aged 75 years and older.

RSV can sometimes also lead to exacerbation of serious conditions such as:

• Asthma
• Chronic obstructive pulmonary disease (COPD)
• Congestive heart failure