# Nirsevimab

Drug · id `maternal:nirsevimab` · Maternal & Newborn Atlas · release `c7fb95f1d15a7d13` (public)

> General information from published sources, not medical advice, and not reviewed by clinicians. Check the cited source before relying on anything here.

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Also called: MEDI8897

Browse, life stage: Newborn; Infant follow-up  
Browse, care area: The baby's first year  

## In plain language

A long-acting antibody against RSV, given to babies as an injection to help prevent severe RSV lung illness. In the MELODY trial it lowered RSV lung infections that needed medical attention in healthy babies born at 35 weeks or later. For hospital admission for RSV, a secondary outcome, the reported result was P = 0.07. The brand name is Beyfortus.

## Technical summary

Substance record (level substance): a monoclonal antibody to the RSV fusion protein with an extended half-life (MELODY abstract). RxNorm ingredient RXCUI 2642401 (RxNav properties); UNII VRN8S9CW5V (US label record in openFDA). The active ingredient is listed in the US drug approvals database as nirsevimab-alip under BLA761328. The antibody is given to the infant, so the infant is both the recipient and the person measured. The registry intervention name is MEDI8897.

## Claims, with the population each applies to

## Context: Healthy late-preterm and term infants born at 35 weeks or later, in their first RSV season (MELODY)

Recipient: Child; Population: 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.; Care setting: International, randomised, placebo-controlled phase 3 trial (many sites across Europe, the Americas, Asia, Africa and Oceania; see the study page).; Geography: 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); Life stage: 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 (245 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).

- Category: Effect
- Evidence stage: Interventional
- Certainty: Certainty not assessed
- Applies to: Recipient: Child; Population: 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.; Care setting: International, randomised, placebo-controlled phase 3 trial (many sites across Europe, the Americas, Asia, Africa and Oceania; see the study page).; Geography: 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); Life stage: 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 (245 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).
- 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.
- Last checked: 2026-10-15
- Sources:
  1. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, METHODS, sentence 3. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  2. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, RESULTS, sentence 3, fragment 1 of 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  3. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, RESULTS, sentence 3, fragment 2 of 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed 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&lt;0.001).

- Category: Effect
- Evidence stage: Interventional
- Certainty: Certainty not assessed
- Applies to: Recipient: Child; Population: 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.; Care setting: International, randomised, placebo-controlled phase 3 trial (many sites across Europe, the Americas, Asia, Africa and Oceania; see the study page).; Geography: 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); Life stage: 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 (245 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).
- 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.
- Last checked: 2026-10-15
- Sources:
  1. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, METHODS, sentence 1, fragment 1 of 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  2. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, METHODS, sentence 1, fragment 2 of 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  3. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, METHODS, sentence 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  4. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, RESULTS, sentence 1. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  5. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, RESULTS, sentence 2, fragment 1 of 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  6. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, RESULTS, sentence 2, fragment 2 of 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  7. Background: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, CONCLUSIONS, sentence 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract (context for the claim).
  8. Background: A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended Lower Respiratory Tract Infection Due to Respiratory Syncytial Virus in Healthy Late Preterm and Term Infants (MELODY) (Registry, edition ClinicalTrials.gov API v2 record, last update posted 2024-02-28.) <https://clinicaltrials.gov/study/NCT03979313>
     Locator: protocolSection.designModule.enrollmentInfo.count. Retrieved 2026-10-15T13:48:53Z. Source state: Current. Snapshot hash: e45fd93804bb04eb549cefae55382ef29c44a5e0e7777f55b68e2693cd421c82.
     How it applies: ClinicalTrials.gov record (context for the claim).
  9. Background: A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended Lower Respiratory Tract Infection Due to Respiratory Syncytial Virus in Healthy Late Preterm and Term Infants (MELODY) (Registry, edition ClinicalTrials.gov API v2 record, last update posted 2024-02-28.) <https://clinicaltrials.gov/study/NCT03979313>
     Locator: protocolSection.eligibilityModule.eligibilityCriteria. Retrieved 2026-10-15T13:48:53Z. Source state: Current. Snapshot hash: e45fd93804bb04eb549cefae55382ef29c44a5e0e7777f55b68e2693cd421c82.
     How it applies: ClinicalTrials.gov record (context for the claim).
  10. Background: A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended Lower Respiratory Tract Infection Due to Respiratory Syncytial Virus in Healthy Late Preterm and Term Infants (MELODY) (Registry, edition ClinicalTrials.gov API v2 record, last update posted 2024-02-28.) <https://clinicaltrials.gov/study/NCT03979313>
     Locator: resultsSection.participantFlowModule.periods\[0\].title. Retrieved 2026-10-15T13:48:53Z. Source state: Current. Snapshot hash: e45fd93804bb04eb549cefae55382ef29c44a5e0e7777f55b68e2693cd421c82.
     How it applies: ClinicalTrials.gov record (context for the claim).
  11. Background: A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended Lower Respiratory Tract Infection Due to Respiratory Syncytial Virus in Healthy Late Preterm and Term Infants (MELODY) (Registry, edition ClinicalTrials.gov API v2 record, last update posted 2024-02-28.) <https://clinicaltrials.gov/study/NCT03979313>
     Locator: resultsSection.participantFlowModule.periods\[1\].title. Retrieved 2026-10-15T13:48:53Z. Source state: Current. Snapshot hash: e45fd93804bb04eb549cefae55382ef29c44a5e0e7777f55b68e2693cd421c82.
     How it applies: ClinicalTrials.gov record (context for the claim).
  12. Background: A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended Lower Respiratory Tract Infection Due to Respiratory Syncytial Virus in Healthy Late Preterm and Term Infants (MELODY) (Registry, edition ClinicalTrials.gov API v2 record, last update posted 2024-02-28.) <https://clinicaltrials.gov/study/NCT03979313>
     Locator: resultsSection.participantFlowModule.periods\[1\].milestones\[0\].achievements\[0\].numSubjects. Retrieved 2026-10-15T13:48:53Z. Source state: Current. Snapshot hash: e45fd93804bb04eb549cefae55382ef29c44a5e0e7777f55b68e2693cd421c82.
     How it applies: ClinicalTrials.gov record (context for the claim).
  13. Background: A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended Lower Respiratory Tract Infection Due to Respiratory Syncytial Virus in Healthy Late Preterm and Term Infants (MELODY) (Registry, edition ClinicalTrials.gov API v2 record, last update posted 2024-02-28.) <https://clinicaltrials.gov/study/NCT03979313>
     Locator: resultsSection.participantFlowModule.periods\[1\].milestones\[0\].achievements\[1\].numSubjects. Retrieved 2026-10-15T13:48:53Z. Source state: Current. Snapshot hash: e45fd93804bb04eb549cefae55382ef29c44a5e0e7777f55b68e2693cd421c82.
     How it applies: ClinicalTrials.gov record (context for the claim).
  14. Background: A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended Lower Respiratory Tract Infection Due to Respiratory Syncytial Virus in Healthy Late Preterm and Term Infants (MELODY) (Registry, edition ClinicalTrials.gov API v2 record, last update posted 2024-02-28.) <https://clinicaltrials.gov/study/NCT03979313>
     Locator: resultsSection.participantFlowModule.periods\[0\].milestones\[0\].achievements\[0\].numSubjects. Retrieved 2026-10-15T13:48:53Z. Source state: Current. Snapshot hash: e45fd93804bb04eb549cefae55382ef29c44a5e0e7777f55b68e2693cd421c82.
     How it applies: ClinicalTrials.gov record (context for the claim).
  15. Background: A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended Lower Respiratory Tract Infection Due to Respiratory Syncytial Virus in Healthy Late Preterm and Term Infants (MELODY) (Registry, edition ClinicalTrials.gov API v2 record, last update posted 2024-02-28.) <https://clinicaltrials.gov/study/NCT03979313>
     Locator: resultsSection.participantFlowModule.periods\[0\].milestones\[0\].achievements\[1\].numSubjects. Retrieved 2026-10-15T13:48:53Z. Source state: Current. Snapshot hash: e45fd93804bb04eb549cefae55382ef29c44a5e0e7777f55b68e2693cd421c82.
     How it applies: ClinicalTrials.gov record (context for the claim).

### In MELODY, serious adverse events were reported in 67 of 987 infants (6.8%) who received nirsevimab and in 36 of 491 infants (7.3%) who received placebo. Among infants with data available to day 361, antidrug antibodies after baseline were detected in 58 of 951 (6.1%) in the nirsevimab group and in 5 of 473 (1.1%) in the placebo group.

- Category: Safety
- Evidence stage: Interventional
- Certainty: Certainty not assessed
- Applies to: Recipient: Child; Population: 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.; Care setting: International, randomised, placebo-controlled phase 3 trial (many sites across Europe, the Americas, Asia, Africa and Oceania; see the study page).; Geography: 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); Life stage: 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 (245 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).
- Limitations: Only the PubMed abstract was read; the full text was not. The abstract does not give the types of serious adverse events or say whether the antidrug antibodies had any clinical effect.
- Last checked: 2026-10-15
- Sources:
  1. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, RESULTS, sentence 4, fragment 1 of 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  2. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, RESULTS, sentence 4, fragment 2 of 2. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.
  3. Supports: Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1056/NEJMoa2110275>
     Locator: Abstract, RESULTS, sentence 5. Retrieved 2026-10-15T13:48:54Z. Source state: Current. Snapshot hash: e10e9dacc692992614d7b67c68e0e85ab8664f8c35669e71c042127f4f51f585.
     How it applies: PubMed abstract.

## Connected pages

- MELODY: medically attended RSV lower respiratory tract infection through 150 days after the injection: RSV lower respiratory tract disease in infants (`maternal:infant-rsv-disease`) [a claim, not a settled fact; see claim `maternal:claim-melody-ma-rsv-lrti` and its context]
- MELODY: hospitalisation for RSV lower respiratory tract infection (secondary end point, P = 0.07): RSV lower respiratory tract disease in infants (`maternal:infant-rsv-disease`) [a claim, not a settled fact; see claim `maternal:claim-melody-hospitalisation` and its context]
- Filed under this front: Medicines and vaccines (`maternal:front-medicines-and-vaccines`)
- Contained in: Beyfortus (nirsevimab) (`maternal:beyfortus`)
- Investigated in: MELODY trial (nirsevimab in healthy late-preterm and term infants) (`maternal:melody-trial`)

## Provenance

Content hash: cfdd7b6175e33b0396334de3b36bb5c3f122048c2eb035018dfa1c0058016516
Last substantive edit: 2026-10-15
Evidence last checked: 2026-10-15