Beyfortus® (nirsevimab-alip) is the first long-acting antibody that helps protect infants for the full respiratory syncytial virus (RSV) season, typically 5 months1,2
ACOG does not recommend repeating the maternal RSV vaccination if an expecting mother has received one in a previous pregnancy.3*
Maternal RSV immunization is not recommended after January 31. Advise your patients to ask their pediatricians about Beyfortus.4
*Clinicians should review the patient's medical records to confirm vaccination status. For patients vaccinated in a previous pregnancy, their infants should receive a monoclonal antibody such as Beyfortus.3,4
On this page
About Beyfortus
Beyfortus is the first long-acting antibody indicated for the prevention of RSV lower respiratory tract disease in1:
- Neonates and infants born during or entering their first RSV season
- Children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season
Fast-acting, passive immunization
Beyfortus is an antibody, not a vaccine, that helps prevent RSV disease in neonates and infants born during or entering their first RSV season.1,2
Protection through the RSV season
Beyfortus provides RSV disease protection through 5 months, the length of a typical RSV season, based on clinical data.1,2*
Administered in the hospital or clinic after birth
Beyfortus can be given in the hospital after birth and prior to discharge to help protect against RSV disease.4,5
Although most of the time RSV will cause mild cold-like symptoms, we cannot predict which infants will develop RSV lower respiratory tract disease.6,7
*Time to maximum concentration is 6 days in adults, and uptake half-life is 1.7 days in infants.1,8
ACOG recommendations
Maternal immunization guidance
ACOG guidelines state that clinicians should counsel patients about both the maternal RSV vaccine and monoclonal antibodies like Beyfortus.3*
Maternal RSV immunization is not recommended for infant protection under the following circumstances3:
- After January 31 during an RSV season in most of the continental United States
- If an expectant mother has already received maternal immunization during a previous pregnancy
- If expectant mothers are not within 32-36 weeks of gestation
If maternal RSV immunization is not provided, ACOG recommends that the infant receive a monoclonal antibody, such as Beyfortus, shortly after birth to protect an infant entering or born during the RSV season.3
Infants <34 weeks
Infants born at <34 weeks should receive Beyfortus, regardless of maternal vaccination status.3
Infants at risk
Infants born to mothers who have received RSV vaccination >14 days before birth may still receive Beyfortus based on clinical judgment.3
*Patient preferences for maternal vs infant immunization against RSV should be considered when deciding to administer Beyfortus.3
Timing of administration3
Timing of RSV vaccine administration for infant protection can vary in different jurisdictions within and outside the continental United States.
In areas with RSV seasonality differing from most of the United States, follow state, local, or territorial RSV epidemiology and guidance for the timing of immunization against RSV.
Maternal immunization guidance
ACOG guidelines state that clinicians should counsel patients about both the maternal RSV vaccine and monoclonal antibodies like Beyfortus.3*
Maternal RSV immunization is not recommended for infant protection under the following circumstances3:
- After January 31 during an RSV season in most of the continental United States
- If an expectant mother has already received maternal immunization during a previous pregnancy
- If expectant mothers are not within 32-36 weeks of gestation
If maternal RSV immunization is not provided, ACOG recommends that the infant receive a monoclonal antibody, such as Beyfortus, shortly after birth to protect an infant entering or born during the RSV season.3
Infants <34 weeks
Infants born at <34 weeks should receive Beyfortus, regardless of maternal vaccination status.3
Infants at risk
Infants born to mothers who have received RSV vaccination >14 days before birth may still receive Beyfortus based on clinical judgment.3
*Patient preferences for maternal vs infant immunization against RSV should be considered when deciding to administer Beyfortus.3
Timing of administration3
Timing of RSV vaccine administration for infant protection can vary in different jurisdictions within and outside the continental United States.
In areas with RSV seasonality differing from most of the United States, follow state, local, or territorial RSV epidemiology and guidance for the timing of immunization against RSV.
CDC and AAP recommendations
First RSV season1,5,9,10
Infants aged <8 months born during or entering their first RSV season are recommended to receive 1 dose of Beyfortus (50 mg for infants <5 kg and 100 mg for infants ≥5 kg) based on maternal vaccine status.
- Providers should target administration shortly before the start of the season for infants aged <8 months born before their first RSV season
- For infants born shortly before or entering their first RSV season, Beyfortus should be administered within 1 week of birth, which can be during the birth hospitalization or in the outpatient setting
CDC recommends administering Beyfortus to infants in specific months during their first RSV season based on RSV seasonality.4
Second RSV season1,9,10
Beyfortus is the only CDC-recommended option for infants and children aged 8 to 19 months at an increased risk of severe RSV disease who are entering their second RSV season (1 dose of Beyfortus [200 mg administered as 2 IM injections 2 x 100 mg]).
- Providers should target administration shortly before the start of the season for children aged 8 to 19 months who are at an increased risk of severe RSV disease
Refer to the most current CDC immunization schedule for additional immunization considerations.
Beyfortus is recommended for infants aged <8 months born during or entering their first RSV season11,12 :
- Whose mother did not receive RSV maternal vaccine or if vaccination status is unknown
- Who were born <14 days after maternal vaccination was administered
- Beyfortus may be considered for infants whose mother received the RSV maternal vaccine if, based on the clinical judgment of the healthcare provider, the potential incremental benefit of administration is warranted
- Current recommendations are if a pregnant woman has received a maternal RSV vaccine during a previous pregnancy, another dose of RSV vaccine is not recommended for subsequent pregnancies. Instead, the baby should receive a monoclonal antibody such as Beyfortus
CDC recommends administering Beyfortus to infants in specific months during their first RSV season based on RSV seasonality.4
Refer to the most current CDC immunization schedule for additional immunization considerations.
Considerations
While CDC guidance states that all infants should receive immune protection during RSV season, maternal immunization is not recommended in the following cases4,5:
- After the month of January in most of the continental United States4
- If an expectant mother has already received maternal immunization during a previous pregnancy4
- If expectant mothers are not within 32-36 weeks of gestation4
- Providers can adjust administration schedule based on local epidemiology because the timing of the onset, peak, and decline of RSV activity might vary geographically9
- RSV seasonality in tropical climates (including Southern Florida, Guam, Hawaii, Puerto Rico, US-affiliated Pacific Islands, and US Virgin Islands) might differ
- In Alaska, RSV seasonality is less predictable, and the duration of RSV activity is often longer than the national average duration
- Providers in these jurisdictions should consult state, local, or territorial guidance on the timing of Beyfortus administration
First RSV season1,5,9,10
Infants aged <8 months born during or entering their first RSV season are recommended to receive 1 dose of Beyfortus (50 mg for infants <5 kg and 100 mg for infants ≥5 kg) based on maternal vaccine status.
- Providers should target administration shortly before the start of the season for infants aged <8 months born before their first RSV season
- For infants born shortly before or entering their first RSV season, Beyfortus should be administered within 1 week of birth, which can be during the birth hospitalization or in the outpatient setting
CDC recommends administering Beyfortus to infants in specific months during their first RSV season based on RSV seasonality.4
Second RSV season1,9,10
Beyfortus is the only CDC-recommended option for infants and children aged 8 to 19 months at an increased risk of severe RSV disease who are entering their second RSV season (1 dose of Beyfortus [200 mg administered as 2 IM injections 2 x 100 mg]).
- Providers should target administration shortly before the start of the season for children aged 8 to 19 months who are at an increased risk of severe RSV disease
Refer to the most current CDC immunization schedule for additional immunization considerations.
Beyfortus is recommended for infants aged <8 months born during or entering their first RSV season11,12 :
- Whose mother did not receive RSV maternal vaccine or if vaccination status is unknown
- Who were born <14 days after maternal vaccination was administered
- Beyfortus may be considered for infants whose mother received the RSV maternal vaccine if, based on the clinical judgment of the healthcare provider, the potential incremental benefit of administration is warranted
- Current recommendations are if a pregnant woman has received a maternal RSV vaccine during a previous pregnancy, another dose of RSV vaccine is not recommended for subsequent pregnancies. Instead, the baby should receive a monoclonal antibody such as Beyfortus
CDC recommends administering Beyfortus to infants in specific months during their first RSV season based on RSV seasonality.4
Refer to the most current CDC immunization schedule for additional immunization considerations.
Considerations
While CDC guidance states that all infants should receive immune protection during RSV season, maternal immunization is not recommended in the following cases4,5:
- After the month of January in most of the continental United States4
- If an expectant mother has already received maternal immunization during a previous pregnancy4
- If expectant mothers are not within 32-36 weeks of gestation4
- Providers can adjust administration schedule based on local epidemiology because the timing of the onset, peak, and decline of RSV activity might vary geographically9
- RSV seasonality in tropical climates (including Southern Florida, Guam, Hawaii, Puerto Rico, US-affiliated Pacific Islands, and US Virgin Islands) might differ
- In Alaska, RSV seasonality is less predictable, and the duration of RSV activity is often longer than the national average duration
- Providers in these jurisdictions should consult state, local, or territorial guidance on the timing of Beyfortus administration
AAP, American Academy of Pediatrics; ACOG, American College of Obstetricians and Gynecologists; CDC, Centers for Disease Control and Prevention; IM, intramuscular.
Resources
Important Safety Information
References: 1. Beyfortus (nirsevimab-alip). Prescribing Information. Sanofi. 2. Obando-Pacheco P, Justicia-Grande AJ, Rivero-Calle I, et al. Respiratory syncytial virus seasonality: a global overview. J Infect Dis. 2018;217(9):1356-1364. 3. Maternal respiratory syncytial virus vaccination. American College of Obstetricians and Gynecologists. Updated October 2025. Accessed January 14, 2026. https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2023/09/maternal-respiratory-syncytial-virus-vaccination 4. Immunizations to protect infants. Centers for Disease Control and Prevention. Updated August 18, 2025. Accessed February 2, 2026. https://www.cdc.gov/rsv/vaccines/protect-infants.html 5. RSV immunization guidance for infants and young children. Centers for Disease Control and Prevention. Updated August 18, 2025. Accessed February 2, 2026. https://www.cdc.gov/rsv/hcp/vaccine-clinical-guidance/infants-young-children.html 6. Arriola CS, Kim L, Langley G, et al. Estimated burden of community-onset respiratory syncytial virus-associated hospitalizations among children aged <2 years in the United States, 2014-15. J Pediatric Infect Dis Soc. 2020;9(5):587-595. 7. RSV in infants and young children. Centers for Disease Control and Prevention. Updated August 30, 2024. Accessed January 14, 2026. https://www.cdc.gov/rsv/infants-young-children/index.html 8. Clegg L, Freshwater E, Leach A, et al. Population pharmacokinetics of nirsevimab in preterm and term infants. J Clin Pharmacol. 2024;64(5):555-567. 9. Jones JM, Fleming-Dutra KE, Prill MM, et al. Use of nirsevimab for the prevention of respiratory syncytial virus disease among infants and young children: recommendations of the Advisory Committee on Immunization Practices—United States, 2023. MMWR Morb Mortal Wkly Rep. 2023;72(34):920-925. 10. Recommended child and adolescent immunization schedule for ages 18 years or younger. American Academy of Pediatrics. Updated January 26, 2026. Accessed February 4, 2026. https://downloads.aap.org/AAP/PDF/AAP-Immunization-Schedule.pdf 11. Fleming-Dutra KE, Jones JM, Roper LE, et al. Use of the Pfizer respiratory syncytial virus vaccine during pregnancy for the prevention of respiratory syncytial virus–associated lower respiratory tract disease in infants: recommendations of the Advisory Committee on Immunization Practices—United States, 2023. MMWR Morb Mortal Wkly Rep. 2023;72(41):1115-1122. 12. RSV vaccine guidance for pregnant women. Centers for Disease Control and Prevention. Updated August 30, 2024. Accessed January 14, 2026. https://www.cdc.gov/rsv/hcp/vaccine-clinical-guidance/pregnant-people.html
