Nirsevimab in a Second RSV Season: AAP and CDC Criteria Differ
-
Click here to listen to this article - Share via
- The American Academy of Pediatrics (AAP) published a policy statement on Sept. 2, 2026, that adds four groups to its list of children aged 8 through 19 months for whom it recommends an RSV antibody in a second season, according to AAP News and the AAP’s HealthyChildren.org page.
- The Centers for Disease Control and Prevention (CDC) lists four groups for that age range, set by a 10-0 vote of its vaccine advisory committee on Aug. 3, 2023, as recorded on CDC’s own evidence page.
- CDC’s evidence page rated the certainty of the second-season evidence as very low, because efficacy was extrapolated from drug levels in a trial with no placebo group, according to the CDC work group.
- The second-season dose is 200 mg, given as two injections, and clesrovimab, the other RSV antibody, is not approved for children entering a second season, according to CDC and the AAP technical report.
- The AAP’s technical report words its chronic lung disease group more broadly than CDC’s “chronic lung disease of prematurity,” adding “other significant neonatal conditions” to the group heading, according to the report.
Table of Contents
- Nirsevimab in a Second RSV Season: The Two Lists
- How the CDC Set Its Four Groups
- Why the AAP Added Four More
- What the Evidence Shows for a Second Dose
- Research Gap: A Second Dose Rests on Indirect Evidence
- Questions Families Can Bring to a Pediatrician
Nirsevimab in a Second RSV Season: The Two Lists
Respiratory syncytial virus, or RSV, is a common virus that can cause serious lung infections in young children. Nirsevimab (Beyfortus) is a monoclonal antibody, a lab-made protein given by injection that targets the virus’s prefusion F protein, the shape of a surface protein the virus uses to enter cells [4].
Two U.S. bodies, the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP), now publish different lists of which children aged 8 through 19 months are recommended a dose as they enter a second RSV season. CDC’s guidance page recommends one 200 mg dose, given as two injections, for children in four groups [1, 2].
CDC’s four groups are:
- Children with chronic lung disease of prematurity, a long-term lung condition after preterm birth, who needed medical support (steroids, diuretics or extra oxygen) at any time in the 6 months before the season began.
- Children with severe immunocompromise, meaning a seriously weakened immune system.
- Children with cystic fibrosis who have severe lung disease or a weight-for-length below the 10th percentile.
- American Indian or Alaska Native children.
The AAP’s policy statement, published online Sept. 2, 2026, adds four groups to its second-season list, AAP News and the AAP’s HealthyChildren.org page reported [5, 8]. The added groups are:
- Children born before 32 weeks of pregnancy, whether or not they needed medication or other support.
- Children with hemodynamically significant congenital heart disease, a heart defect that can cause symptoms or enlarge a heart chamber.
- Children with anatomic pulmonary abnormalities or neuromuscular disorders that raise RSV risk.
- Children with Down syndrome or other chromosomal differences that raise risk.
The AAP’s accompanying technical report lists eight groups in all. Its entries for severe immunocompromise, cystic fibrosis with severe lung disease or low weight-for-length, and American Indian and Alaska Native children match CDC’s in substance [4].
The lung disease group is worded more broadly than CDC’s, which names chronic lung disease of prematurity. The technical report’s heading for the group reads chronic lung disease “or other significant neonatal conditions.” The Association of Immunization Managers summary of the AAP guidance words it as chronic lung disease attributed to prematurity or other significant conditions [4, 6].
Under that heading, the report describes children with chronic lung disease who needed steroids, diuretics or oxygen in the 6 months before the season [4]. The heading therefore widens CDC’s wording, while the description under it still centers on chronic lung disease needing that support.
CDC’s guidance page for infants and young children carries an Aug. 18, 2025 date stamp, and its evidence page for the second season is dated Sept. 5, 2024, both before the AAP’s 2026 statement [1, 2].
How the CDC Set Its Four Groups
CDC’s vaccine advisory panel, the Advisory Committee on Immunization Practices (ACIP), voted 10-0 on Aug. 3, 2023, to recommend a second-season dose for children at increased risk [1].
CDC’s evidence page says its work group defined risk using the groups the AAP had identified for palivizumab, an older antibody given monthly, plus American Indian and Alaska Native children [1]. CDC’s guidance page, dated Aug. 18, 2025, says palivizumab would no longer be available starting Dec. 31, 2025 [2].
The work group also looked beyond those groups. A systematic review of 3,825 abstracts found 6 studies, which showed higher RSV hospitalization risk in children with chronic lung disease, congenital heart disease and neuromuscular disease, and no studies on other conditions [1].
CDC then analyzed a national insurance claims database, MarketScan, for 2015 to 2021. The page lists the conditions studied as chronic lung disease, congenital heart disease, Down syndrome, neuromuscular disease, pulmonary malformations, immunodeficiency and cystic fibrosis, and says hospitalization rates were increased for all of them. It cautions that RSV testing may be more common in children with such conditions, which could inflate RSV-specific hospitalization rates [1].
The page describes the Medley trial, a phase 2/3 pharmacokinetics and safety study, as including palivizumab-eligible children with hemodynamically significant congenital heart disease and chronic lung disease for the second season, and no other conditions [1].
Why the AAP Added Four More
The abstract of the AAP’s policy statement says a review of evidence supports expanding the high-risk criteria, and it points to an accompanying technical report for the evidence [3].
The technical report says that, with nirsevimab costing less per dose than palivizumab and needing one administration per season, the AAP set out in 2026 to review the literature and identify the children most likely to benefit during their second season. It cites a 2025 surveillance study of 12 states in which 23.4% of children aged 12 through 23 months hospitalized with RSV had an underlying medical condition. It also says 92% of children with intensive-care-level second-season RSV hospitalizations were ineligible for second-season immunization under the guidelines in place before the 2026 expansion [4].
Sean T. O’Leary, MD, MPH, who leads the RSV immunization subgroup of the AAP Committee on Infectious Diseases, said the added groups are a relatively small population, as AAP News reported [5]. When they are hospitalized, he said, their length of stay tends to be longer.
The technical report and AAP News tie the added groups to hospital burden for specific conditions [4, 5]. CDC’s work group started from the palivizumab list and the evidence available in 2023, and also analyzed hospitalization rates [1].
Both bodies name nirsevimab as the antibody for a second season. Clesrovimab, another RSV antibody, is not approved for children entering a second season [2, 4]. The Association of Immunization Managers summary says the AAP’s second-season recommendation applies regardless of the pregnant parent’s vaccination status or the child’s earlier receipt of an RSV antibody [6].
What the Evidence Shows for a Second Dose
Most efficacy data come from a first RSV season. In infants born during or entering their first season, pooled phase 2 and 3 trials found nirsevimab was 79.0% effective against medically attended RSV lung infection and 80.6% effective against infection requiring hospitalization, measured through 150 days after injection [2].
Early real-world data showed it was at least 70% effective in keeping babies out of the hospital with RSV, according to CDC [2].
For the second season, CDC’s page says direct efficacy data are absent. In the Medley trial, no child had a medically attended RSV lung infection in the second season, which ran in 2020 during the COVID-19 pandemic. The work group used drug exposure, measured from blood levels, as a stand-in for efficacy, and more than 90% of the high-risk children in the trial had exposure above the target [1].
On safety, CDC’s page reports that about 9 to 10% of children who received nirsevimab in the second season had a serious adverse event, against none among those who received palivizumab, and the trial investigators judged none to be related to the product [1]. CDC’s page reports a relative risk of 8.4 for serious adverse events against palivizumab, meaning the rate was 8.4 times as high in the nirsevimab group [1].
The page also says the serious adverse events were not significantly different between the two groups [1]. CDC lists pain, redness or swelling at the injection site as the usual side effects, and says the antibody is contraindicated in children with a history of severe allergic reaction to any of its components [2].
Research Gap: A Second Dose Rests on Indirect Evidence
The CDC work group rated the overall certainty of the second-season evidence as very low. Its page lists four reasons for the downgrade: drug-level data stood in for efficacy, the trial population did not match the proposed indication, the study was small, and it had no placebo group [1].
Risk falls for most children after 12 months, the AAP technical report says, though some stay at increased risk [4]. In CDC’s surveillance data, the RSV hospitalization rate in infants aged 6 to 11 months was 1.9 times the rate in children aged 12 to 23 months [1].
Questions Families Can Bring to a Pediatrician
Whether a particular child falls on either list is a decision for that child’s pediatrician. Questions a family can raise with the pediatrician include:
- Whether the child’s condition is named on the CDC list, the AAP list or both.
- Whether a time-limited condition, such as chronic lung disease needing support in the 6 months before the season, applies.
- Whether an earlier RSV antibody dose changes anything, since the Association of Immunization Managers summary says the AAP recommendation applies regardless of earlier receipt [6].
- How the dose would be handled by the child’s insurer if the condition appears only on the AAP list.
For children for whom CDC recommends a dose, CDC says the best timing is shortly before the season, typically October or November. Antibody is given October through March in most of the country [2]. CDC’s guidance page also says CDC does not currently recommend nirsevimab for anyone aged 20 months or older [2].
Coverage is a separate question. ACIP voted to include nirsevimab in the Vaccines for Children program as part of its 2023 recommendation process, and the program provides immunizations at no cost to children who might not otherwise be immunized because of inability to pay [1].
KFF reports that the Affordable Care Act’s no-cost-sharing requirement for private plans applies to immunizations that have an ACIP recommendation adopted by the CDC Director [9]. Medical Daily reported that recommendations from medical societies do not automatically trigger these coverage requirements [7].
CDC’s cost analysis used a dose cost of $890. It estimated about $1.5 million per quality-adjusted life year, a standard measure of health gained, for the general population. At 10 times the baseline hospitalization risk, it estimated about $300,000 per quality-adjusted life year if only hospitalization rates rose, and about $25,000 if the death rate per hospitalization rose as well [1].
References
1. Centers for Disease Control and Prevention. (2024, September 5). ACIP evidence to recommendations for use of nirsevimab in children 8-19 months of age at increased risk of severe disease entering their second RSV season. https://www.cdc.gov/acip/evidence-to-recommendations/nirsevimab-season2-rsv-infants-children-etr.html
2. Centers for Disease Control and Prevention. (2025, August 18). RSV immunization guidance for infants and young children. https://www.cdc.gov/rsv/hcp/vaccine-clinical-guidance/infants-young-children.html
3. American Academy of Pediatrics, Committee on Infectious Diseases. (2026). Recommendations for the prevention of respiratory syncytial virus disease in infants and children: Policy statement. Pediatrics. Advance online publication. https://doi.org/10.1542/peds.2026-079047
4. American Academy of Pediatrics, Committee on Infectious Diseases. (2026). Recommendations for the prevention of respiratory syncytial virus disease in infants and children: Technical report. Pediatrics. Advance online publication. https://doi.org/10.1542/peds.2026-079049
5. Jenco, M. (2026, September 2). AAP expands high-risk groups recommended for RSV immunization in second season. AAP News. https://publications.aap.org/aapnews/news/35919/AAP-expands-high-risk-groups-recommended-for-RSV
6. Association of Immunization Managers. (2026, September 2). Summary of 2026-2027 respiratory syncytial virus vaccine and monoclonal antibody product indications and recommendations. https://www.immunizationmanagers.org/content/uploads/2026/09/This-Just-In_RSVGuidance-Updates_090226.pdf
7. Vega, E. (2026, September 3). Pediatricians widen the RSV high risk list and more toddlers now qualify for a second season dose. Medical Daily. https://www.medicaldaily.com/aap-rsv-immunization-guidance-2026-expanded-high-risk-toddlers-478159
8. American Academy of Pediatrics. (2026, September 2). AAP releases RSV immunization recommendations for 2026-2027 season. HealthyChildren.org. https://www.healthychildren.org/English/news/Pages/aap-updates-rsv-immunization-recommendations-for-2026-2027-season.aspx
9. Kates, J. (2025, June 13). ACIP, CDC, and insurance coverage of vaccines in the United States. KFF. https://www.kff.org/other-health/acip-cdc-and-insurance-coverage-of-vaccines-in-the-united-states/
