Healthcare Providers: RSV Prevention Information

RSV Immunization for Infants and Young Children

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Respiratory syncytial virus (RSV) is the most common cause of hospitalization in infants and can cause serious illness and death in infants and young children.

Severe RSV lower respiratory tract infection  in infants can be prevented either by administering monoclonal antibody products to infants and young children, or by administering RSV vaccine during pregnancy.

There are two injectable monoclonal antibody products that help protect infants and young children from lower respiratory tract infection caused by RSV.

  • Nirsevimab (Beyfortus)
  • Palivizumab (Synagis)

There is one RSV vaccine (Abrysvo, Pfizer) recommended for pregnant persons to prevent severe RSV lower respiratory tract infection in their infants.

Recommendations for Using Nirsevimab

One dose of nirsevimab is recommended for infants younger than 8 months of age who were born shortly before or are entering their first RSV season (typically fall through spring) if

  • The mother did not receive RSV vaccine during pregnancy.
  • The mother’s RSV vaccination status is unknown.
  • The infant was born within 14 days of maternal RSV vaccination.

Except in rare circumstances, nirsevimab is not needed for most infants younger than age 8 months who are born 14 or more days after their mother received RSV vaccine. For additional details, see section on special situations and populations.

Additionally, a dose of nirsevimab is recommended for some children aged 8 through 19 months old who are at increased risk for severe RSV disease and entering their second RSV season. The following children aged 8 through 19 months are recommended to get a dose shortly before or during their second RSV season:

  • American Indian/Alaska Native children
  • Children with chronic lung disease of prematurity who require medical support during the six months before the start of their second RSV season
  • Children with severe immunocompromise
  • Children with severe cystic fibrosis

Children ages 8 months and older who are not at increased risk of severe RSV disease should not receive nirsevimab.

Considerations for the use of nirsevimab or palivizumab in infants and young children at increased risk for severe RSV disease are available at ACIP and AAP Recommendations for the Use of the Monoclonal Antibody Nirsevimab for the Prevention of RSV Disease.

Timing of Nirsevimab Administration

While the timing of the onset and duration of RSV season may vary, nirsevimab may be administered October through the end of March in most of the continental United States. The timing of the onset, peak, and decline of RSV activity vary geographically, and providers may adjust timing of administration based on guidance from public health authorities (e.g., CDC, health departments) or regional medical centers.

Although optimal timing of administration is just before the start of the RSV season, nirsevimab may also be administered during the RSV season to infants and children who are age-eligible..

Contraindications and Precautions

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.

It should be given with caution to infants and children with bleeding disorders. See General Best Practice Guidelines for Immunization for details on vaccinating persons with increased risk for bleeding.

Children who have a moderate or severe acute illness should usually wait until they recover before getting nirsevimab.

About Nirsevimab

Nirsevimab is an injectable monoclonal antibody that prevents severe RSV disease in infants and young children.  Monoclonal antibodies do not activate the immune system, as would occur with infection or vaccination (active immunization). Rather, the antibodies themselves protect against disease (i.e., passive immunization).

Because nirsevimab does not activate the immune system, protection is likely most effective the weeks after nirsevimab is given and wanes over time. Nirsevimab does not provide long-term immunity to RSV disease but provides protection to infants when they are most at risk of getting severe RSV disease. As children get older, they are less likely to get severe symptoms from RSV infection.

Nirsevimab Efficacy

In infants younger than age 8 months 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%, efficacy in preventing RSV-associated LRTI with hospitalization was 80.6%, and efficacy in preventing RSV-associated LRTI with admission to an intensive care unit (ICU) was 90.0%.

Nirsevimab Safety

Among all participants in the phase 2 and 3 clinical trials, adverse events were reported within 360 days of the injection in 1.2% of participants who received nirsevimab. Most (97%) of these were mild to moderate in intensity. Adverse reactions that were more common among infants who received nirsevimab than placebo was rash occurring within 14 days of injection (0.9% of nirsevimab recipients versus 0.6% of placebo recipients) and injection site reactions occurring within 7 days of injection (0.3% of nirsevimab recipients versus 0% of placebo recipients).

The incidence of serious adverse events was not increased in the nirsevimab arm compared with that in the placebo arm. No adverse events of anaphylaxis or immune complex disease were reported.

Among the initially enrolled 1,490 infants in the phase 3 trial, the incidence of medically attended RSV-associated LRTI 351–510 days after injection was not significantly different in the nirsevimab (0.7%) and control (0.2%) arms, suggesting that protection provided from nirsevimab does not result in a shift in the RSV burden to the second year of life.

Storage and Handling of Nirsevimab

Proper storage and handling of nirsevimab is essential to ensure it is effective in preventing RSV disease.

Nirsevimab is supplied as pre-filled syringes for one time use only. It comes in two doses:

  • 50 mg/0.5 ml
  • 100 mg/ml

The pre-filled syringes should be stored refrigerated between 36°F to 46°F (2°C to 8°C) and may be kept at room temperature 68°F to 77°F (20°C to 25°C) for a maximum of 8 hours.  They should be stored in the original carton to protect from light until time of use. Do not freeze or expose to heat.

After removal from the refrigerator, they must be used within 8 hours or discarded. Do not use nirsevimab beyond the expiration date printed on the label.

Administering Nirsevimab

This page provides a summary for administering nirsevimab, including route, number of doses, and simultaneous administration with vaccine products.

Route

Administer nirsevimab intramuscularly. The preferred site of administration is the anterolateral thigh region. Do not administer nirsevimab intravenously, intradermally, or subcutaneously. 

Number and Timing of Doses

Infants younger than 8 months of age who were born during or are entering their first RSV season should receive nirsevimab if

  • The mother did not receive RSV vaccine during pregnancy.
  • The mother’s RSV vaccination status is unknown.
  • The infant was born within 14 days of maternal RSV vaccination.

When indicated, nirsevimab should be administered shortly before or during the RSV season.

  • Infants born during the RSV season should receive a single dose of nirsevimab (50 mg for infants <5 kg and 100 mg for infants ≥5 kg) in the first week of life. The dose can be administered either in the birth hospital or outpatient clinic. Infants with prolonged hospitalization (e.g., preterm infants) should be immunized shortly before or promptly after discharge. Nirsevimab administration should be offered during the season to those who have not received a dose.
  • In infants younger than age 8 months born outside the RSV season, a single dose of nirsevimab (50 mg for infants <5 kg and 100 mg for infants ≥5 kg) is recommended. Administration should be targeted shortly before the start of their first RSV season and continued during the season for those who have not received a dose.
  • In children ages 8 through 19 months who are at increased risk of severe RSV disease, administration of a single 200 mg dose of nirsevimab should be targeted shortly before the start of their second RSV season and continued during the season for those who have not received a dose.

The onset and duration of the RSV season varies from year to year. Based on pre-pandemic patterns, this means nirsevimab could be administered in most of the continental United States from October through the end of March. Optimal timing for nirsevimab administration is shortly before the RSV season begins; however, nirsevimab may be administered to age-eligible infants and children who have not yet received a dose at any time during the season. Only a single dose of nirsevimab is recommended for an RSV season [except in children undergoing cardiac surgery with cardiopulmonary bypass (see nirsevimab FDA package insert)]. Because timing of the onset, peak, and decline of RSV activity may vary, providers can adjust administration schedules based on local epidemiology. 

Administration with Vaccine Products

Nirsevimab can be administered without regard to timing of routine childhood vaccines. This includes simultaneous administration (i.e., same clinic day) with vaccine products. No interval between nirsevimab and live vaccines (such as MMR and Varicella) is necessary.

Nirsevimab is not expected to interfere with the immune response to vaccine products. There is limited experience with administering nirsevimab with vaccine products. In clinical trials, when nirsevimab was given concomitantly with routine childhood vaccines, the safety and reactogenicity profile of the co-administered regimen was similar to the childhood vaccines given alone.

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