RSV lower respiratory tract disease in infants

Overview

Recognition

In very young infants the only symptoms may be irritability, decreased activity and trouble breathing (MedlinePlus).

Assessment

MedlinePlus says a lab test of nasal fluid or another respiratory specimen can check for RSV, usually for people with severe infection.

Burden

• Burden Evidence stage not applicable Certainty not assessed

  MedlinePlus describes RSV as a common respiratory virus that usually causes mild, cold-like symptoms but can cause serious lung infections, especially in infants, and says nearly all children become infected with RSV by age 2. In very young infants the only symptoms may be irritability, decreased activity and trouble breathing. FDA's 2023 news release called RSV the most frequent cause of lower respiratory tract illness in infants worldwide and, citing the Centers for Disease Control and Prevention, the leading cause of infant hospitalisation in the United States.

  Applies to Child

  • Infants and young children, the group MedlinePlus and FDA describe as most affected by serious RSV illness. The MedlinePlus page also covers older adults and people with weakened immune systems, who are outside this context.
  • Not stated (general health information and an FDA news release).
  • General; the FDA statement about hospitalisation names the United States
  • Infants from birth, and children up to about 2 years
  • Gestational age Not reported
  • Postnatal age Not reported

  Follow-up Not applicable (descriptive statements)

  Certainty method

  Not assessed

  Limitations

  These are statements by a health information service and by FDA, not incidence studies, and neither gives numbers. The FDA statement about hospitalisation is FDA's report of a CDC statement; CDC's own source was not read.

  Last checked

  2026-10-15

  Next evidence check due

  Not scheduled

  Sources and citations (6)

  1. Supports Respiratory Syncytial Virus Infections (MedlinePlus health topic)

     Webpage · MedlinePlus, National Library of Medicine · Edition The health topic page as shown on 2026-10-15. The page carries no edition date.

     Locator

     Summary, What is RSV?, sentences 1 and 2

     How it applies

     MedlinePlus health topic summary.

     Retrieved

     2026-10-15T13:49:53Z

     Source effective date

     Not reported

     Source state

     Current

     Snapshot hash

     234a38a10cca920623a2eae8c2ac85ffb8edeb6ee17a5f6b9fe58d976db69de7

     Reuse basis

     MedlinePlus page Linking to and Using Content (fetched as ml-medlineplus-using-content.html, sha256 f70c0b8c67574e30377aab0c22b44038364a37e2e9f54a2ffa67597383b3de34) lists summaries on health topic pages as public-domain content. The page bytes are not committed. Short quotations with attribution.

  2. Supports Respiratory Syncytial Virus Infections (MedlinePlus health topic)

     Webpage · MedlinePlus, National Library of Medicine · Edition The health topic page as shown on 2026-10-15. The page carries no edition date.

     Locator

     Summary, What is RSV?, sentence 3

     How it applies

     MedlinePlus health topic summary.

     Retrieved

     2026-10-15T13:49:53Z

     Source effective date

     Not reported

     Source state

     Current

     Snapshot hash

     234a38a10cca920623a2eae8c2ac85ffb8edeb6ee17a5f6b9fe58d976db69de7

     Reuse basis

     MedlinePlus page Linking to and Using Content (fetched as ml-medlineplus-using-content.html, sha256 f70c0b8c67574e30377aab0c22b44038364a37e2e9f54a2ffa67597383b3de34) lists summaries on health topic pages as public-domain content. The page bytes are not committed. Short quotations with attribution.

  3. Supports Respiratory Syncytial Virus Infections (MedlinePlus health topic)

     Webpage · MedlinePlus, National Library of Medicine · Edition The health topic page as shown on 2026-10-15. The page carries no edition date.

     Locator

     Summary, Who is at risk?, sentence 1 (part)

     How it applies

     MedlinePlus health topic summary.

     Retrieved

     2026-10-15T13:49:53Z

     Source effective date

     Not reported

     Source state

     Current

     Snapshot hash

     234a38a10cca920623a2eae8c2ac85ffb8edeb6ee17a5f6b9fe58d976db69de7

     Reuse basis

     MedlinePlus page Linking to and Using Content (fetched as ml-medlineplus-using-content.html, sha256 f70c0b8c67574e30377aab0c22b44038364a37e2e9f54a2ffa67597383b3de34) lists summaries on health topic pages as public-domain content. The page bytes are not committed. Short quotations with attribution.

  4. Supports Respiratory Syncytial Virus Infections (MedlinePlus health topic)

     Webpage · MedlinePlus, National Library of Medicine · Edition The health topic page as shown on 2026-10-15. The page carries no edition date.

     Locator

     Summary, What are the symptoms?, paragraph 2

     How it applies

     MedlinePlus health topic summary.

     Retrieved

     2026-10-15T13:49:53Z

     Source effective date

     Not reported

     Source state

     Current

     Snapshot hash

     234a38a10cca920623a2eae8c2ac85ffb8edeb6ee17a5f6b9fe58d976db69de7

     Reuse basis

     MedlinePlus page Linking to and Using Content (fetched as ml-medlineplus-using-content.html, sha256 f70c0b8c67574e30377aab0c22b44038364a37e2e9f54a2ffa67597383b3de34) lists summaries on health topic pages as public-domain content. The page bytes are not committed. Short quotations with attribution.

  5. Supports FDA Approves First Vaccine for Pregnant Individuals to Prevent RSV in Infants (FDA news release)

     Regulator · U.S. Food and Drug Administration · Edition Press announcement dated August 21, 2023. The page says its content was current as of 08/22/2023. · Published 2023-08-21

     Locator

     Paragraph 3, sentence 2

     How it applies

     FDA news release.

     Retrieved

     2026-10-15T13:49:54Z

     Source effective date

     2023-08-22

     Source state

     Current

     Snapshot hash

     a9e38eeb5dbd394c4f249e8b4d31fc3c3355e93cb9f55b6dfe2607eb460623d9

     Reuse basis

     FDA website policies page (fetched as ml-fda-website-policies.html, sha256 55a5b4fce88a043c5ae9dfb1f0ce276b5bd3cef79755ca246907c70272b848a1) says that, unless otherwise noted, the contents of www.fda.gov are not copyrighted, are in the public domain, and may be republished without permission. The bytes are not committed. Short quotations with attribution.

  6. Supports FDA Approves First Vaccine for Pregnant Individuals to Prevent RSV in Infants (FDA news release)

     Regulator · U.S. Food and Drug Administration · Edition Press announcement dated August 21, 2023. The page says its content was current as of 08/22/2023. · Published 2023-08-21

     Locator

     Paragraph 3, sentence 7

     How it applies

     FDA news release.

     Retrieved

     2026-10-15T13:49:54Z

     Source effective date

     2023-08-22

     Source state

     Current

     Snapshot hash

     a9e38eeb5dbd394c4f249e8b4d31fc3c3355e93cb9f55b6dfe2607eb460623d9

     Reuse basis

     FDA website policies page (fetched as ml-fda-website-policies.html, sha256 55a5b4fce88a043c5ae9dfb1f0ce276b5bd3cef79755ca246907c70272b848a1) says that, unless otherwise noted, the contents of www.fda.gov are not copyrighted, are in the public domain, and may be republished without permission. The bytes are not committed. Short quotations with attribution.

Claims and evidence

Clinical links

Each link reports what one cited claim says about one population. "Evaluated for" means studied, not shown to work. These links do not show that anything is effective or right for you.

• Claim, not a settled fact Evaluated for this: Nirsevimab (Evaluated for, seen from the other side)

  Applies to Child

  • Healthy infants in their first year of life, born at or after 35 weeks 0 days of gestation, who were entering their first RSV season at screening. Infants who met national or local criteria for palivizumab were excluded. The abstract randomised 1490 infants in the primary cohort.
  • International, randomised, placebo-controlled phase 3 trial (many sites across Europe, the Americas, Asia, Africa and Oceania; see the study page).
  • Argentina, Australia, Austria, Belgium, Bulgaria, Canada, Chile, Colombia, Czechia, Estonia, Finland, France, Germany, Israel, Italy, Japan, Latvia, Lithuania, Mexico, New Zealand, Panama, Poland, Russia, South Africa, South Korea, Spain, Sweden, Turkey (Türkiye), Ukraine, the United Kingdom and the United States (ClinicalTrials.gov locations)
  • Infants from birth to 1 year of age, dosed before or at the start of their first RSV season
  • Gestational age at least 35 weeks 0 days, measured at birth
  • Postnatal age Not reported

  Follow-up 150 days after the injection for the efficacy end points; follow-up to day 361 for safety and antidrug antibodies (abstract).
  In the MELODY trial, infants born at a gestational age of at least 35 weeks were randomly assigned 2:1 to a single intramuscular injection of nirsevimab or placebo before the start of an RSV season. Medically attended RSV-associated lower respiratory tract infection through 150 days after the injection occurred in 12 infants (1.2%) in the nirsevimab group and in 25 infants (5.0%) in the placebo group, an efficacy of 74.5% (95% confidence interval 49.6 to 87.1; P<0.001).

  Limitations. Only the PubMed abstract was read; the full text was not. The abstract counts 1490 infants randomised: 994 to nirsevimab and 496 to placebo. ClinicalTrials.gov lists 3012 enrolled; its participant flow lists the Primary Cohort of 496 placebo and 994 nirsevimab infants (the 1490 the abstract randomised) and, for All Subjects, 1003 placebo and 2009 nirsevimab infants. The trial was funded by MedImmune/AstraZeneca and Sanofi. The trial studied healthy late-preterm and term infants; it says nothing about infants born before 35 weeks.

• Claim, not a settled fact Evaluated for this: Nirsevimab (Evaluated for, seen from the other side)

  Applies to Child

  • Healthy infants in their first year of life, born at or after 35 weeks 0 days of gestation, who were entering their first RSV season at screening. Infants who met national or local criteria for palivizumab were excluded. The abstract randomised 1490 infants in the primary cohort.
  • International, randomised, placebo-controlled phase 3 trial (many sites across Europe, the Americas, Asia, Africa and Oceania; see the study page).
  • Argentina, Australia, Austria, Belgium, Bulgaria, Canada, Chile, Colombia, Czechia, Estonia, Finland, France, Germany, Israel, Italy, Japan, Latvia, Lithuania, Mexico, New Zealand, Panama, Poland, Russia, South Africa, South Korea, Spain, Sweden, Turkey (Türkiye), Ukraine, the United Kingdom and the United States (ClinicalTrials.gov locations)
  • Infants from birth to 1 year of age, dosed before or at the start of their first RSV season
  • Gestational age at least 35 weeks 0 days, measured at birth
  • Postnatal age Not reported

  Follow-up 150 days after the injection for the efficacy end points; follow-up to day 361 for safety and antidrug antibodies (abstract).
  In MELODY, hospitalisation for RSV-associated lower respiratory tract infection through 150 days after the injection, the secondary efficacy end point, occurred in 6 infants (0.6%) in the nirsevimab group and in 8 infants (1.6%) in the placebo group (efficacy 62.1%; 95% confidence interval -8.6 to 86.8; P = 0.07).

  Limitations. Only the PubMed abstract was read; the full text was not. This is a secondary end point, and the abstract reports P = 0.07 for it. The abstract does not describe it as meeting or missing a prespecified criterion. The trial was funded by MedImmune/AstraZeneca and Sanofi.

• Claim, not a settled fact Evaluated for this: RSV vaccination in pregnancy to protect the infant (Evaluated for, seen from the other side)

  Applies to Newborn

  • Infants of the women randomised in MATISSE. The 24 to 36 week window is the mother's gestational age at vaccination; it is not a limit on the infant's gestational age at birth, which the abstract does not restrict. The abstract evaluated 3570 infants of vaccinated women and 3558 infants of placebo recipients.
  • Prenatal and paediatric care settings in 18 countries (international, placebo-controlled trial).
  • 18 countries listed in ClinicalTrials.gov (see the MATISSE study page)
  • Infants from birth, with RSV illness counted within 90, 120, 150 and 180 days after birth
  • Gestational age Not reported
  • Postnatal age Not reported

  Follow-up RSV-associated illness within 90, 120, 150 and 180 days after birth; safety follow-up of infants and toddlers up to 24 months of age (abstract).
  In the phase 3, double-blind MATISSE trial, pregnant women at 24 through 36 weeks' gestation were randomly assigned 1:1 to a single intramuscular injection of 120 micrograms of a bivalent RSV prefusion F protein vaccine (RSVpreF) or placebo. At a prespecified interim analysis the success criterion was met for one primary end point. Medically attended severe RSV-associated lower respiratory tract illness within 90 days after birth occurred in 6 infants of women in the vaccine group and 33 infants of women in the placebo group (vaccine efficacy 81.8%; 99.5% confidence interval 40.6 to 96.3); 19 cases and 62 cases, respectively, occurred within 180 days after birth (vaccine efficacy 69.4%; 97.58% confidence interval 44.3 to 84.1).

  Limitations. Only the PubMed abstract was read; the full text was not. The result is from an interim analysis, and only one of the two primary end points met the statistical success criterion (see the separate claim on illness of any severity). The abstract gives 99.5% intervals at 90 days and 97.58% intervals at later time points. Women were vaccinated at 24 through 36 weeks in the trial, a wider window than the 32 through 36 weeks FDA approved. The trial was funded by Pfizer.

• Claim, not a settled fact Evaluated for this: RSV vaccination in pregnancy to protect the infant (Evaluated for, seen from the other side)

  Applies to Newborn

  • Infants of the women randomised in MATISSE. The 24 to 36 week window is the mother's gestational age at vaccination; it is not a limit on the infant's gestational age at birth, which the abstract does not restrict. The abstract evaluated 3570 infants of vaccinated women and 3558 infants of placebo recipients.
  • Prenatal and paediatric care settings in 18 countries (international, placebo-controlled trial).
  • 18 countries listed in ClinicalTrials.gov (see the MATISSE study page)
  • Infants from birth, with RSV illness counted within 90, 120, 150 and 180 days after birth
  • Gestational age Not reported
  • Postnatal age Not reported

  Follow-up RSV-associated illness within 90, 120, 150 and 180 days after birth; safety follow-up of infants and toddlers up to 24 months of age (abstract).
  In MATISSE, medically attended RSV-associated lower respiratory tract illness of any severity within 90 days after birth occurred in 24 infants of women in the vaccine group and 56 infants of women in the placebo group (vaccine efficacy 57.1%; 99.5% confidence interval 14.7 to 79.8). The authors state that these results did not meet the statistical success criterion.

  Limitations. Only the PubMed abstract was read; the full text was not. This is one of the trial's two primary end points, reported at the interim analysis, and the statistical success criterion was not met for it. The abstract does not say whether later analyses changed this result. The trial was funded by Pfizer.

Record details

Record id

maternal:infant-rsv-disease

Content hash

6ba87e682433602738a8e77130749c05fa763ee2e128318d6a94062e7559680f