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Respiratory syncytial virus infection

Last reviewed: 8 Nov 2023
Last updated: 04 Oct 2023
04 Oct 2023

FDA and EMA approve first vaccine for pregnant women to prevent RSV infection in infants, as well as new drug to prevent RSV infection in infants

In July/August 2023, the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) approved Abrysvo®, the first respiratory syncytial virus (RSV) vaccine to gain approval for use in pregnant women to prevent RSV infection in infants. It is a bivalent RSV prefusion F (RSVpreF) protein-based vaccine for use at 32 to 36 weeks' gestational age of pregnancy, to prevent RSV in infants up to 6 months of age. It was proven to be effective with a favorable safety profile in large randomized controlled trials. The vaccine had previously also been recently approved for the prevention of lower respiratory tract diseases caused by RSV in individuals 60 years and older.

This comes after the approval of the immunoprophylactic drug nirsevimab to prevent RSV infection in infants and children. Nirsevimab is an RSV F protein-directed fusion inhibitor monoclonal antibody and has an advantage over current immunoprophylaxis options because it is longer acting and only requires one dose. The safety and efficacy of nirsevimab were supported by three clinical trials. In July 2023, the Center for Disease Control and Prevention's Advisory Committee on Immunization Practices (ACIP) recommended that infants ages <8 months born during or entering their first RSV season, and infants and children ages 8-19 months who are at increased risk of severe RSV disease and entering their second RSV season, receive one intramuscular dose of nirsevimab.

Together, these medications represent a breakthrough in preventing RSV infection. The Center for Disease Control and Prevention (CDC) estimates that 2% to 3% of children under 12 months of age in the US are hospitalized each year due to RSV. The CDC also estimates that 60,000 to 160,000 older adults in the US are hospitalized each year due to RSV infections, and approximately 6000 to 10,000 older adults die each year from RSV-related illness.

See Management: prevention

Original source of update



History and exam

Key diagnostic factors

  • exposure to RSV
  • infants at high risk for RSV infection
  • winter season
  • older adult age
  • immune deficit
  • rhinorrhea/congestion
  • tachypnea
  • increased work of breathing
  • cough
  • wheeze
  • poor feeding
  • cyanosis
  • rales
  • apnea
More key diagnostic factors

Other diagnostic factors

  • fever
Other diagnostic factors

Risk factors

  • exposure to RSV
  • hemodynamically significant congenital heart disease
  • history of prematurity
  • immune deficit
  • chronic lung disease
  • high-risk infants with no recent immunoprophylaxis against RSV
  • infants aged <6 months
  • winter season
  • older adult age
  • smoke exposure
  • family history of asthma
  • Down syndrome
More risk factors

Diagnostic investigations

1st investigations to order

  • pulse oximetry
More 1st investigations to order

Investigations to consider

  • chest x-ray
  • hydration status
  • direct fluorescent antibody staining of respiratory specimen (e.g., nasopharyngeal aspirate)
  • reverse transcriptase polymerase chain reaction of respiratory specimen (e.g., nasopharyngeal aspirate)
  • viral culture of respiratory specimen (e.g., nasopharyngeal aspirate)
More investigations to consider

Treatment algorithm


mild or self-limited illness

moderate illness

severe illness



Giovanni Piedimonte, MD, FAAP, FCCP

Vice President for Research

Professor of Pediatrics, Biochemistry, & Molecular Biology

Tulane University School of Medicine

New Orleans



GP declares that he has no competing interests.

Margot Anderson, MD

Assistant Professor of Clinical Pediatrics

Section of Infectious Diseases and Hospital Medicine

Tulane University School of Medicine

Tulane University

New Orleans



MA will be the principal investigator for a phase 3 trial to evaluate the safety, efficacy, and pharmacokinetics of MK-1654 in infants and children at increased risk for severe respiratory syncytial virus disease, based at Tulane University School of Medicine. Merck will reimburse Tulane University for participation.


Dr Giovanni Piedimonte and Dr Margot Anderson would like to gratefully acknowledge Dr Frank Esper and Dr Melvin L. Wright, previous contributors to this topic.


FE is on an advisory board for Procter and Gamble. MLW declares that he has no competing interests.

Peer reviewers

Leonard R. Krilov, MD


Pediatric Infectious Disease

Vice Chairman

Department of Pediatrics

Children's Medical Center

Winthrop University Medical Center


Professor of Pediatrics

School of Medicine

Stony Brook University Medical Center

Stony Brook



LRK has participated as an investigator in multiple clinical research trials supported by grants from MedImmune. LRK has also served as a consultant to MedImmune on medical advisory boards and is a member of their speakers' bureau.

Robert Welliver, MD

Professor of Pediatrics

Women and Children's Hospital




RW declares that he has no competing interests.

Jennifer Handforth, MB ChB, MRCPCH, DTM&H

Consultant Paediatrician

Croydon University Hospital




JH declares that she has no competing interests.

  • Respiratory syncytial virus infection images
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