Respiratory Syncytial Virus (RSV)

Advisory Committee on Immunization Practices (ACIP) Recommendations

Infants

• Infants 0-8 months of age entering or born during their first Respiratory Syncytial Virus (RSV) season (October-March) should receive 1 dose of nirsevimab (trade name: Beyfortus^TM)¹, unless their mother received RSV vaccine during pregnancy at least two weeks before birth, in which case nirsevimab is not needed for most infants (though it can still be considered in the rare circumstances when its potential incremental benefit is warranted, such as for infants at increased risk of severe RSV disease).²

Children

• Children 8-19 months of age entering their second RSV season and at increased risk of severe RSV disease should receive 1 dose of nirsevimab.⁴  

Adults

• All adults at least 75 years of age should receive a single dose of RSV vaccine (trade names: Arexvy, Abrysvo™).
• Adults 60-74 years of age at increased risk of severe RSV disease should also receive a single dose of RSV vaccine.⁵

For More Information

• ACIP Recommendations: https://www.cdc.gov/acip-recs/hcp/vaccine-specific/rotavirus.html
• Immunization Schedules: http://www.cdc.gov/vaccines/schedules/index.html 

Important Information for Obstetric Providers

• RSVpreF vaccine (Abrysvo^TM) is routinely recommended during weeks 32-36 of pregnancy using seasonal administration (September-January in most of the continental US; in jurisdictions with differing seasonality, follow local guidance).²

Disease

Respiratory syncytial virus (RSV) is an RNA virus of the genus Orthopneumovirus. There are two main types of human RSV (Type A and Type B). Most subtypes are determined by antigenic drift and duplications in RSV-G sequences, but may also have genome-wide sequence divergence. This makes RSV relatively adept at evading immunity induced by prior infection or vaccination.³

RSV is a common cause of lower respiratory tract disease (LRTD), with symptoms such as runny nose, coughing, sneezing, wheezing, fever, and decreased appetite. Although RSV is usually mild, it can cause severe illness, including pneumonia and bronchiolitis, and may also lead to worsening of existing conditions, such as asthma, chronic obstructive pulmonary disease (COPD), and congestive heart failure. Symptoms typically appear within 4-6 days after infection, and infected persons may become contagious a day or two before showing any symptoms. RSV spreads through droplets from coughing and sneezing, but also can survive for hours on hard surfaces and spread by touching one’s face after touching a contaminated surface.

Premature infants, young children with congenital heart or chronic lung disease, children with neuromuscular disorders, persons with compromised immune systems, and older adults (especially those with pre-existing heart or lung disease) are at the highest risk for severe disease. Every year in the US, RSV is estimated to cause 58,000-80,000 hospitalizations and 100–300 deaths among children less than 5 years old, and 60,000-160,000 hospitalizations and 6,000-10,000 deaths among adults 65 years and older.⁷

Vaccine

Two RSV vaccines are licensed for use among adults at least 60 years of age in the United States: RSVPreF3 (Arexvy) and RSVpreF (Abrysvo™). Both vaccines contain 120µg of antigen and are administered as a single 0.5mL dose via intramuscular injection. RSVPreF3 includes an AS01 adjuvant, and RSVpreF is bivalent.^5,8,9 RSVpreF is also licensed for use among pregnant individuals between 32 and 36 weeks gestational age.^8,10 One passive immunization (monoclonal antibody) against RSV, nirsevimab (trade name: Beyfortus^TM), is licensed for use among children up to 2 years of age.¹¹ It is administered as a single intramuscular injection of: 50 mg for infants less than 5 kg, 100 mg for infants more than 5 kg, and 200 mg for children at least 8 months of age.¹²

Contraindications and Precautions

Severe allergic reaction (e.g. anaphylaxis) to a previous dose or vaccine component is a contraindication to immunization with RSV vaccines or monoclonal antibody.^8,9,10 Current moderate to severe acute illness is a precaution to any vaccination.¹³

Vaccine Effectiveness

Clinical trials found RSVPreF3 to be 83% effective against RSV-associated LRTD and 94% effective against severe RSV-associated LRTD among adults at least 60 years of age.¹⁴ Clinical trials among adults at least 60 years of age found RSVpreF to be 62% effective against RSV-associated acute respiratory illness, 67% effective against RSV-associated LRTD with at least two symptoms, and 86% effective against RSV-associated LRTD with at least three symptoms.¹⁵ Clinical trials among pregnant individuals found RSVpreF to be 82% effective within 90 days after birth and 69% effective within 180 days after birth against RSV-associated severe LRTD; and among the subgroup vaccinated between 32 and 36 weeks gestational age, trials found RSVpreF to be 91% effective within 90 days after birth and 77% effective within 180 days after birth against RSV-associated severe LRTD.¹⁰ Clinical trials found nirsevimab to reduce medically attended RSV-associated LRTD by 79% and RSV-associated hospitalization by 81% among infants in their first RSV season.^1,11

Vaccine Safety

The most commonly reported side effects among RSVPreF3 vaccine recipients in the clinical trial were injection site pain (61%), fatigue (34%), myalgia (29%), headache (27%), and arthralgia (18%). Ten RSVPreF3 vaccine recipients in the clinical trial experienced atrial fibrillation within 30 days of vaccination, compared to four placebo recipients. There were no other imbalances between study arms for categories of adverse events, but three other serious adverse events following immunization were noted: one participant developed GBS 9 days after RSVPreF3 vaccination, and two participants developed ADEM 7 and 22 days after concomitant RSVPreF3 and influenza vaccination, respectively.^9,14

Local reactions occurred in 12% of RSVPreF vaccine recipients (compared to 7% of placebo recipients) in the clinical trial among adults at least 60 years of age. Most local reactions were mild to moderate and transient. The most common local reaction experienced was injection site pain (11%). Systemic events (such as fatigue, headache, and fever) and severe events occurred in similar amounts among vaccine and placebo recipients. Three serious adverse events were considered related to the vaccine by the trial investigators: one participant had a delayed allergic reaction 7 hours after vaccination, one developed Miller-Fisher syndrome 8 days after vaccination, and one developed myocardial infarction 6 days after vaccination and GBS 7 days after vaccination.^8,15.

The most commonly reported side effects among RSVPreF vaccine recipients in the clinical trial among pregnant individuals were pain at the injection site (41%), headache (31%), muscle pain (27%), and nausea (20%). Slightly higher rates of pre-eclampsia (1.8% vs 1.4%), low birth weight (5.1% vs 4.4%), preterm birth (5.7% vs 4.7%), and neonatal jaundice (7.2% vs 6.7%) were found in pregnant individuals receiving the vaccination (or their infants) compared to those receiving placebo.^8,10.

The most common adverse reactions to nirsevimab in clinical trials were rash (0.9%) and injection site reactions (0.3%).¹²

Preliminary safety surveillance data presented to ACIP on February 29th, 2024, suggested a potential increased risk for GBS after RSV vaccination among adults at least 60 years of age, but estimated that the benefits of RSV vaccination outweighed potential risks such as GBS.¹⁶ Updated safety surveillance data presented to ACIP on June 26th, 2024, supported this interpretation, as the estimated numbers of avertable deaths, hospitalizations, and ICU admissions were much larger than potential GBS cases for both RSV vaccines among all age groups.¹⁷ Further studies are ongoing to confirm and more accurately quantify this suspected association. See the Do Vaccines Cause Guillain-Barré Syndrome? summary for more details.

Considerations in Pregnancy

RSVPreF is licensed for use among pregnant individuals between 32 and 36 weeks gestational age,^8,10 and routinely recommended for those individuals whose weeks 32-36 of pregnancy overlap with RSV season (which is September-January in most of the continental US; in other jurisdictions with differing seasonality, follow local guidance).¹⁸

References

1.         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 Morbidity and mortality weekly report. Aug 25 2023;72(34):920-925. doi:10.15585/mmwr.mm7234a4

2.         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 Morbidity and mortality weekly report. Oct 13 2023;72(41):1115-1122. doi:10.15585/mmwr.mm7241e1

3.         World Health Organization. Respiratory Syncytial Virus (RSV) disease. Accessed June 29, 2023. https://www.who.int/teams/health-product-policy-and-standards/standards-and-specifications/vaccine-standardization/respiratory-syncytial-virus-disease

4.         CDC Recommends a Powerful New Tool to Protect Infants from the Leading Cause of Hospitalization. August 3, 2023. https://www.cdc.gov/media/releases/2023/p-0803-new-tool-prevent-infant-hospitalization-.html

5.         Melgar M, Britton A, Roper LE, et al. Use of Respiratory Syncytial Virus Vaccines in Older Adults: Recommendations of the Advisory Committee on Immunization Practices – United States, 2023. MMWR Morbidity and mortality weekly report. Jul 21 2023;72(29):793-801. doi:10.15585/mmwr.mm7229a4

6.         Britton A, Roper LE, Kotton CN, et al. Use of Respiratory Syncytial Virus Vaccines in Adults Aged ≥60 Years: Updated Recommendations of the Advisory Committee on Immunization Practices – United States, 2024. MMWR Morbidity and mortality weekly report. Aug 15 2024;73(32):696-702. doi:10.15585/mmwr.mm7332e1

7.         Centers for Disease Control and Prevention. Respiratory Syncytial Virus Infection (RSV). Updated October 28, 2022. Accessed June 29, 2023. https://www.cdc.gov/rsv/index.html

8.         Food and Drug Administration. Package Insert – ABRYSVO. Accessed June 29, 2023. https://www.fda.gov/media/168889/download

9.         Food and Drug Administration. Package Insert – AREXVY. Accessed June 29, 2023. https://www.fda.gov/media/167805/download

10.       FDA Approves First Vaccine for Pregnant Individuals to Prevent RSV in Infants. August 21, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-first-vaccine-pregnant-individuals-prevent-rsv-infants

11.       FDA Approves New Drug to Prevent RSV in Babies and Toddlers. July 17, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-new-drug-prevent-rsv-babies-and-toddlers

12.       Food and Drug Administration. Package Insert – BEYFORTUS. Updated July 2023. Accessed August 4, 2023. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/761328s000lbl.pdf

13.       Epidemiology and Prevention of Vaccine-Preventable Diseases. 2015.

14.       FDA Approves First Respiratory Syncytial Virus (RSV) Vaccine. May 3, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-first-respiratory-syncytial-virus-rsv-vaccine

15.       Walsh EE, Pérez Marc G, Zareba AM, et al. Efficacy and Safety of a Bivalent RSV Prefusion F Vaccine in Older Adults. The New England journal of medicine. Apr 20 2023;388(16):1465-1477. doi:10.1056/NEJMoa2213836

16.       Centers for Disease Control and Prevention. February 2024 ACIP Meeting. 2024:

17.       Centers for Disease Control and Prevention. June 2024 ACIP Meeting. 2024:

18.       CDC recommends new vaccine to help protect babies against severe respiratory syncytial virus (RSV) illness after birth. September 22, 2023. https://www.cdc.gov/media/releases/2023/p0922-RSV-maternal-vaccine.html