RSV Immunization: What Parents Should Know About Protecting Newborns

Updated November 2025

Recent approvals for new RSV immunization strategies have parents wondering whether the maternal RSV vaccine given during pregnancy or the monoclonal RSV antibody shot given at birth is right for their families.

Respiratory Syncytial Virus (RSV) is a common respiratory infection that peaks in the fall and winter months, and for some infants, it can lead to severe illness. This post provides an overview of RSV and the available immunization options so you can make informed decisions about protecting your infant.

Personal note from Dr. Ashley: Many parents in my community have had questions about these two new RSV immunizations. This information is presented to help you make an informed choice along with your healthcare provider. I support all parents regardless of vaccine choices.

What Is RSV?

RSV is a highly contagious virus that usually causes mild cold-like symptoms in healthy individuals, such as a runny nose, cough, or low-grade fever. However, for certain at-risk groups, including infants under 12 months, RSV may develop into a serious condition, like bronchiolitis or pneumonia, which may require hospital care. 

Read more about RSV: RSV (Respiratory Syncytial Virus) – Treatment & Prevention.

How RSV Spreads

RSV spreads through:

• Respiratory droplets (from coughs or sneezes)
• Direct contact (e.g., handshakes or kisses)
• Contaminated surfaces (e.g., toys or countertops)

Anyone of any age can get an RSV infection, and repeat infections are possible. People are contagious for 1-2 days before symptoms appear and usually stop being contagious after symptoms disappear. An exception is infants and those with weakened immune systems who may spread RSV for up to 4 weeks after symptoms have disappeared (1,2). 

The incubation period (the time between coming in contact with the virus and showing symptoms) is 2-8 days (2). 

Serious RSV Outcomes

RSV is the leading cause of hospitalization in infants under 1 year old in the United States (3). 

For every 1,000 infants:

• 0–2 months old: 24 are hospitalized (4)
• 3–5 months old: 13 are hospitalized (4)
• 6–11 months old: 8 are hospitalized (4)

Such hospitalizations can be distressing, but most infants recover within 2-4 days with appropriate hospital care (2). 

Whether or not there are long term negative impacts from RSV, infection is a subject of much research. At present, the consensus is that serious RSV infections may increase the chances of wheezing but not asthma later in life (2). 

The RSV related mortality rate is quite low in infants in high income countries like the United States, but unfortunately there are still RSV-related deaths every year (5). Globally, RSV is responsible for an estimated 100,000 deaths per year in children under 5 years old. 97% of these deaths occur in low and middle income countries (6).  

RSV Immunization Options for Newborns

In 2023, two new immunization options for infants were approved by the FDA. The first is a vaccine given during pregnancy (Abrysvo) so that the mother produces RSV-antibodies that are passed to the child through the placenta. The second is a monoclonal antibody (Nirsevimab/Beyfortus) given after birth that directly supplies monoclonal antibodies to the child. 

In 2025 another monoclonal antibody, Clesrovimab (Enflonsia) was approved by the FDA, while the older monoclonal antibody (Palivizumab/Synagis) which had been approved for over two decades was discontinued.

For more information, see this webpage: RSV (Respiratory Syncytial Virus) Immunizations | CDC

1. Maternal RSV Vaccine (Abrysvo – FDA Approved in 2023) 

Who it’s for: 

• Pregnant people at 32–36 weeks gestation between the months of September – January

How it works: 

• Administered during pregnancy, it prompts the mother’s immune system to create RSV antibodies, which are passed to the baby via the placenta.

Protection window: 

• Covers the infant’s first 6 months of life, when RSV risks are highest.

Efficacy:

• Reduces hospitalization risk by 68% at 3 months and 57% at 6 months.
• Lowers severe RSV outcomes (e.g., ICU admission) by 82% at 3 months and 69% at 6 months.

Considerations:

• Not recommended before 32 weeks or after 36 weeks and 6 days of pregnancy
• Immunocompromised people may have a diminished response to the RSV vaccine
• Discuss with your healthcare provider, especially if you have a high-risk pregnancy
• Still in post-marketing clinical trials; early post-marketing information contributes to suspicions of increased risk of premature birth and lists other adverse events. The FDA is monitoring this closely. See the results here: Safety of RSV Vaccine among Pregnant Individuals: A Real-World Pharmacovigilance Study Using Vaccine Adverse Event Reporting System | medRxiv

2. Infant RSV Antibody Injection (Beyfortus/Nirsevimab – FDA Approved in 2023)

Who it’s for: 

• Infants whose mothers didn’t get maternal RSV vaccination or were vaccinated less than two weeks before giving birth, or for those whose mother’s RSV vaccination status is unknown
• Infants born during non-peak RSV seasons
• Beyfortus covers both first season and second season (for high risk children under 19 months of age entering their second RSV season)

How it works: 

• A one-time weight-dependent injection provides immediate passive immunity by delivering pre-made RSV antibodies.

Protection window: 

• Up to 5 months of immunity.

Efficacy:

• Pooled efficacy from Phase II and III clinical trials in preventing medically attended RSV-associated lower respiratory tract infection (LRTI) was 79.0% and efficacy in preventing RSV-associated LRTI with hospitalization was 80.6% (7).

Considerations:

• May be used as a complement to maternal vaccination (rarely) or as an alternative for infants who didn’t receive antibody protection via their mother
• Still in post-marketing clinical trials
• At Dr. Green Mom, we prefer Beyfortus/Nirsevimab over maternal RSV vaccination due to slightly more favorable efficacy and safety data.

3. Infant RSV Antibody Injection (Clesrovimab/Enflonsia – FDA Approved in 2025)

Who it’s for: 

• Infants whose mothers didn’t get maternal RSV vaccination or were vaccinated less than two weeks before giving birth, or for those whose mother’s RSV vaccination status is unknown
• Infants aged <8 months born during or entering their first RSV season who are not already protected through maternal RSV vaccination.
• Enflonsia is not indicated for children entering second RSV (7).

How it works: 

• A one-time, non-weight dependent injection provides immediate passive immunity by delivering pre-made RSV antibodies.

Protection window: 

• Up to 5 months of immunity.

Efficacy:

• Among infants who were born during or entering their first RSV season, efficacy for preventing medically attended RSV-associated LRTI was 60.4%, and efficacy for preventing RSV-associated LRTI with hospitalization was 90.9% through 150 days after injection (7).

Considerations:

• May be used as a complement to maternal vaccination (rarely) or as an alternative for infants who didn’t receive antibody protection via their mother

Both Nirsevimab and Clesrovimab are contraindicated in infants and children with a history of severe allergic reactions (e.g., anaphylaxis) to any components or excipients in the product. 

4. Infant RSV Antibody Injection (Palivizumab/Synagis – FDA Approved in 1998)

• Discontinued Dec. 2025

Timing of RSV Immunizations

The timing of RSV immunizations and the immunization that you’re offered depends on the month your infant is born in and whether you live in an area with predictable RSV patterns.* The following schedules may not apply to you; discuss with your healthcare provider. 

1. Abrysvo – RSV Vaccine

• Offered to people who give birth from September – January

2. Beyfortus/Nirsevimab and Enflonsia/Clesrovimab RSV Monoclonal Antibody

• Offered at birth to infants born October – March
• Offered in October to infants born April – September

See this page and speak with your doctor for more information: Immunizations to Protect Infants | RSV | CDC

*Applies to most of the continental United States. Timing of administration for RSV immunization may differ in certain areas.

Other Protective Measures

• Breastfeeding: Offers natural immunity, reducing RSV-related hospitalization and the need for oxygen therapy. Even partial breastfeeding provides some protection (7). Estimates of the protection offered by breastfeeding have a wide range, see this article for more details: Impact of breastfeeding on the incidence and severity of respiratory syncytial virus (RSV)-associated acute lower respiratory infections in infants: a systematic review highlighting the global relevance of primary prevention
• Hygiene Practices: Wash hands frequently, clean surfaces, don’t let people hold and kiss your baby, and limit exposure to crowded places during RSV season (8).

Making an Informed Decision

RSV immunization options—maternal vaccine and infant antibodies—are tools to help parents reduce the risks of severe RSV infections. None of the RSV protection options offer 100% protection against RSV, and the majority of hospitalizations occur in otherwise healthy infants with no known risk factors. Therefore, it is important to remain vigilant about hygiene and distancing measures during RSV season regardless of underlying risk factors, breastfeeding practices, or immunization status. 

For a deeper dive into the risks and benefits of all three immunization options, download our free RSV eBook. It goes into finer detail about immunization efficacy and known adverse events. It also unpacks some of the controversy you may have heard around these vaccines to help you make confident decisions. 

Download your free eBook here. 

If this is the type of information that you’d like to have for all routine childhood vaccines, consider purchasing the Vaccine Strategy Guide.

Summary

RSV awareness is essential in protecting your baby’s health. Good hygiene and reducing the number of people in close contact with your infant are needed regardless of underlying risk factors or immunization status. 

The RSV vaccine and monoclonal antibodies offer parents more choices for additional layers of protection. By understanding the benefits and risks of each option, you can make the best decision for your family. Speak with your healthcare provider to help determine the choice that is right for you.

Resources:

We have resources that go deeper into all things vaccines to help you make informed choices for your family. Check out our popular Vaccine Strategy Guide. 

For further information, you may find these links helpful:

• CDC RSV information
• Statement on the prevention of respiratory syncytial virus disease in infants – Canada.ca
• Abrysvo (Maternal RSV Vaccine) package insert
• Abrysvo Monograph
• Abrysvo FDA approval letter
• Beyfortus/Nirsevimab (Infant Monoclonal Antibodies) package insert
• Beyfortus Monograph
• Beyfortus/Nirsevimab FDA approval letter
• Enflonsia/Clevorsimab(Monoclonal Antibodies) package insert
• Enflonsia/Clevorsimab approval letter
• Synagis/Palivizumab (High Risk Infant Monoclonal Antibodies) package insert
• Synagis Monograph
• Synagis first FDA approval letter 

References:

1. CDC. (2024). How RSV Spreads. https://www.cdc.gov/rsv/causes/index.html
2. Jain H, Schweitzer JW, & Justice NA. (2024). Respiratory Syncytial Virus Infection in Children. [Updated 2023 Jun 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. https://www.ncbi.nlm.nih.gov/books/NBK459215/
3. Suh, M., Movva, N., Jiang, X., Bylsma, L. C., Reichert, H., Fryzek, J.P., & Nelson, C.B. (2022). Respiratory Syncytial Virus Is the Leading Cause of United States Infant Hospitalizations, 2009-2019: A Study of the National (Nationwide) Inpatient Sample. The Journal of infectious diseases, 226(Suppl 2), S154–S163. https://doi.org/10.b1093/infdis/jiac120
4. Curns, A.T., Rha, B., Lively, J.Y., Sahni, L.C., Englund, J.A., Weinberg, G.A., Halasa, N.B., Staat, M.A., Selvarangan, R., Michaels, M., Moline, H., Zhou, Y., Perez, A., Rohlfs, C., Hickey, R., Lacombe, K., McHenry, R., Whitaker, b., Schuster, J., Pulido, C.G., Strelitz, B., Quigley, C., Weddle DNP, G., Avadhanula, V., Harrison, C.J., Stewart, L.S., Schlaudecker, E., Szilagyi, P.G., Klein, E.J., Boom, J., Williams, J.V., Langley, G., Gerber, S.I., Hall, A.J., McMorrow, M.L.. (2024). Respiratory Syncytial Virus-Associated Hospitalizations Among Children <5 Years Old: 2016 to 2020. Pediatrics March 2024; 153 (3): e2023062574. 10.1542/peds.2023-062574
5. Byington, C.L., Wilkes, J., Korgenski, K., & Sheng, X. (2015). Respiratory syncytial virus-associated mortality in hospitalized infants and young children. Pediatrics, 135(1), e24–e31. https://doi.org/10.1542/peds.2014-2151
6. Munro, A.P.S., Martinón-Torres, F., Drysdale, S.B., & Faust, S.N. (2023). The disease burden of respiratory syncytial virus in Infants. Current opinion in infectious diseases, 36(5), 379–384. https://doi.org/10.1097/QCO.0000000000000952
7. CDC. (2025). RSV Immunization Guidance for Infants and Young Children. https://www.cdc.gov/rsv/hcp/vaccine-clinical-guidance/infants-young-children.html
8. Mineva GM, Purtill H, Dunne CP, et al. (2023). Impact of breastfeeding on the incidence and severity of respiratory syncytial virus (RSV)-associated acute lower respiratory infections in infants: a systematic review highlighting the global relevance of primary prevention. BMJ Global Health 2023;8:e009693.
9. Gastaldi, A., Donà, D., Barbieri, E., Giaquinto, C., Bont, L. J., & Baraldi, E. (2021). COVID-19 Lesson for Respiratory Syncytial Virus (RSV): Hygiene Works. Children (Basel, Switzerland), 8(12), 1144. https://doi.org/10.3390/children8121144