What to know
- To prevent severe RSV disease in infants, either maternal RSV vaccination or infant immunization with the RSV monoclonal antibody (nirsevimab) is recommended. Most infants will not need both.
- Administration of nirsevimab is recommended during October through March in most of the U.S. The optimal timing for nirsevimab administration is shortly before the RSV season begins (e.g., October–November), or within a baby's first week of life if born October through March (ideally during the birth hospitalization.)
- Nirsevimab is highly effective in preventing RSV-associated hospitalization.
- Side effects are usually mild, such as pain, redness, or swelling where the injection was given, and resolve quickly. Hypersensitivity reactions are uncommon but have been reported with nirsevimab and similar antibody products.
Overview
Nirsevimab is a monoclonal antibody that prevents severe RSV disease and is recommended for infants and some young children.
Monoclonal antibodies are not vaccines. They do not activate the immune system. Rather, the antibodies themselves protect against disease.
Healthcare providers should discuss both the RSV maternal vaccine (Pfizer’s Abrysvo) and nirsevimab with parents and consider patient preferences when deciding which product is best for their family.
Recommendations
Recommendation for infants
Nirsevimab is recommended for infants younger than 8 months of age who are born during or are entering their first RSV season (typically fall through spring) if:
- The mother did not receive RSV vaccine during pregnancy, or
- The mother’s RSV vaccination status is unknown, or
- The infant was born within 14 days of maternal RSV vaccination.
The child's age on the day nirsevimab is administered should be used to determine if the child is eligible for immunization. Except in rare circumstances, nirsevimab is not needed for most infants who are born 14 or more days after their mother received RSV vaccine.
Providers should talk to parents and recommend nirsevimab for eligible babies. Ideally, babies born during October through March receive nirsevimab during their birth hospitalization. However, administration can occur during any visit to a healthcare setting, including well-child visits.
Recommendation for some young children
Nirsevimab is recommended for some children (ages 8 through 19 months) who are at increased risk for severe RSV disease and entering their second RSV season. The following children ages 8 through 19 months are recommended to get nirsevimab shortly before or as early as possible during their second RSV season:
- Children with chronic lung disease of prematurity who required medical support (chronic corticosteroid therapy, diuretic therapy, or supplemental oxygen) any time during the 6-month period before the start of the second RSV season
- Children with severe immunocompromise
- Children with cystic fibrosis who have either 1) manifestations of severe lung disease (previous hospitalization for pulmonary exacerbation in the first year of life or abnormalities on chest imaging that persist when stable), or 2) weight-for-length <10th percentile
- American Indian or Alaska Native children
Children ages 8 months and older who are not at increased risk of severe RSV disease should not receive nirsevimab. CDC does not currently recommend nirsevimab for anyone aged 20 months or older.
American Academy of Pediatrics (AAP) publishes recommendations for palivizumab, including considerations for use of palivizumab in the setting of nirsevimab recommendations.
Additional considerations
Seasonal administration
Nirsevimab should be administered October through the end of March in most of the continental United States.
Infants born during the seasonal administration window (October 1 through March 31) should get nirsevimab within one week after birth - ideally during the birth hospitalization. Throughout March, any eligible infant or young child who has not yet received a recommended dose should receive nirsevimab at the earliest opportunity.
For infants born outside of the seasonal administration window (April through September) and for young children who are at increased risk for severe RSV disease and entering their second RSV season, the optimal timing for nirsevimab administration is shortly before the RSV season begins (e.g., October or November).
Because the timing of the onset, peak, and decline of RSV activity varies geographically, public health authorities (e.g., CDC, health departments) or regional medical centers may provide additional guidance for nirsevimab administration for their jurisdictions.
Administration in locations with different or unpredictable RSV circulation patterns
ACIP recommendations allow for nirsevimab to be administered before October or after March. Tropical climates may have RSV circulation patterns that differ from most of the continental United States or are unpredictable. Locations with tropical climates include but are not limited to southern Florida, Guam, Hawaii, Puerto Rico, US-Affiliated Pacific Islands, and the US Virgin Islands. In Alaska, RSV circulation patterns are less predictable, and the duration of RSV season is often longer than the national average. Public health authorities or regional medical centers may elect to provide revised clinical and public health guidance regarding the ideal timing of nirsevimab administration based on local epidemiology and feasibility of implementation, including local supply considerations.
Administration using clinical judgement
Healthcare providers may use clinical judgement in determining when to give nirsevimab and give nirsevimab outside of October through March. Special circumstances may also need to be considered, such as travel to areas with increased RSV activity or concerns that the infant or child may not return for a visit when nirsevimab should ideally be administered.
Flexibilities in the ACIP recommendations on the timing of nirsevimab administration should be considered to optimize patient access, including reimbursement of nirsevimab.
When nirsevimab can be considered for infants born to vaccinated mothers
Nirsevimab may be considered for infants born to vaccinated mothers in rare circumstances when, based on the clinical judgment of the healthcare provider, the potential incremental benefit of administration is warranted. These circumstances may include, but are not limited to:
- Infants born to mothers who may not mount an adequate immune response to RSV vaccination (e.g., people with immunocompromising conditions)
- Infants born to mothers who have medical conditions associated with reduced transplacental antibody transfer (e.g., people living with HIV infection)
- Infants who have undergone cardiopulmonary bypass (see nirsevimab FDA package insert) or extracorporeal membrane oxygenation (ECMO), leading to loss of maternal antibodies
- Infants with substantial increased risk for severe RSV disease (e.g., hemodynamically significant congenital heart disease, intensive care admission with a requirement of oxygen at discharge)
Dosage
- Age less than 8 months
- 50 mg for infants weighing <5 kg [<11 lb]
- 100 mg for infants weighing ≥5 kg [≥11 lb]
- Age 8 through 19 months:
- 200 mg, administered as two 100 mg injections
Coadministration with vaccines
There are limited data with administering nirsevimab with other childhood vaccines. However, nirsevimab is not expected to interfere with the immune response to vaccine products.
Nirsevimab and routine childhood vaccines can be administered during the same visit. No interval between nirsevimab and live vaccines (such as measles, mumps, and rubella [MMR] and varicella) is necessary.
Effectiveness
Early real-world data show that nirsevimab was at least 80–90% effective in preventing babies from being hospitalized with RSV.
In clinical studies in infants who were born during or entering their first RSV season, efficacy was evaluated through 150 days after injection. Pooled efficacy from phase 2 and 3 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%.
Safety
Contraindications
Nirsevimab is contraindicated in infants and children with a history of severe allergic reactions (e.g., anaphylaxis) to nirsevimab or to any of its components. See nirsevimab FDA package insert.
Precautions
Nirsevimab should be given with caution to infants and children with bleeding disorders. See General Best Practice Guidelines for Immunization for details on immunizing persons with increased risk for bleeding.
In accordance with CDC's General Best Practice Guidelines for Immunization, children who have a moderate or severe acute illness should usually wait until they recover before getting nirsevimab.
Reporting adverse events
Adverse reactions might occur after administration of nirsevimab alone; these reactions may be reported to MedWatch online, by fax, by mail, or by contacting FDA at 1-800-FDA-1088.
Adverse reactions might occur after the coadministration of nirsevimab with a vaccine; these reactions should be reported to the Vaccine Adverse Event Reporting System (VAERS), and reports should specify that the patient received nirsevimab on the VAERS form in Section 9: "Prescriptions, over-the-counter medications, dietary supplements, or herbal remedies being taken at the time of vaccination." Reports can be submitted to VAERS online, by fax, or by mail. Additional information about VAERS is available by telephone (1-800-822- 7967) or online. When adverse reactions that occur after the coadministration of nirsevimab with a vaccine are reported to VAERS, additional reporting of the same adverse reactions to MedWatch is not necessary.
To learn more about RSV vaccine safety, go to the following page:
