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The CDC's Advisory Committee on Immunization Practices (ACIP) voted unanimously -- 10 to 0 -- in favor of nirsevimab (Beyfortus) for protecting a wide swath of at-risk infants from respiratory syncytial virus (RSV).

At a meeting on Thursday, ACIP recommended that all infants younger than 8 months who are born during or approaching their first RSV season receive one dose of nirsevimab.

The advisory committee also voted 10-0 to recommend that children 8 to 19 months who are at increased risk of severe RSV and approaching their second RSV season receive one dose of the monoclonal antibody against RSV.

RSV is the most common cause of hospitalization among infants in the U.S.

"This is a milestone," said Sarah Long, MD, chair of ACIP's Maternal Pediatric RSV Work Group and a pediatric infectious diseases expert at Drexel University College of Medicine in Philadelphia. "This is the very first antibody protection against a remaining burden of disease in children. So, parents should be very, very much relieved that they won't have to be concerned about the likelihood that their child could be hospitalized with the RSV disease."

Following the meeting, CDC Director Mandy Cohen, MD, MPH, .

Importantly, the ACIP recommendation defined the increased-risk group of infants 8 to 19

Importantly, the ACIP recommendation defined the increased-risk group of infants 8 to 19 months along the lines of the American Academy of Pediatrics' (AAP) recommendation for another anti-RSV monoclonal antibody, palivizumab (Synagis):

• Chronic lung disease of prematurity requiring medical support in the 6 months before the second RSV season

• Severe immunocompromise

• Cystic fibrosis with pulmonary exacerbation hospitalization by age 1 year or persistent abnormalities on chest imaging when stable or weight-for-length <10th percentile

The committee also added Alaska Native and Native American toddlers to this at-risk group, given multiple studies documenting the increased incidence of RSV-associated hospitalizations in this demographic. While this group represents much less than 1% of the American population of children ages 8-19 months, their risk is in the range of six to 10 times greater than the population at large, Long said.

As with every "breakthrough" there are new responsibilities, and so the work group had discussions with the members of the FDA Adverse Event Reporting System and the CDC's Vaccine Safety Datalink "to be sure that this new innovation is in fact safe," Long said.

"There was absolutely no signal that there was anything that would interfere or that there was any adverse event experienced in the small trials that were done," she added.

In discussion prior to the vote, working group members highlighted a number of implementation challenges ranging from internal provider ordering, to reporting administration of nirsevimab in immunization information systems, to obtaining reimbursement for counseling.

Most of these issues stem from the fact that nirsevimab is coded as a therapeutic and not a vaccine, explained Georgina Peacock, MD, MPH, director of the Immunization Services Division for the CDC's National Center for Immunization and Respiratory Diseases.

The first season with nirsevimab availability will be seen as a transition period, she added.

Jamie Loehr, MD, the owner of Cayuga Family Medicine in Ithaca, New York, spoke of the development of nirsevimab as a "spectacular advancement ... and 2 years from now, it'll be covered by insurances and all the implementation [will] be in place."

While fully supportive of the recommendation for infants younger than 8 months, Loehr expressed some reluctance around the proposed recommendation for children 8 to 19 months at increased risk of RSV.

"It's a very expensive proposal. It is a lot of extrapolation," he said, referring to the fact that pharmacokinetic data was used as a surrogate for efficacy data in studies of this age group.

Long explained that the proposed recommendation for the older infants includes the same population who, under the AAP's recommendations, would be receiving palivizumab (Synagis), which is "much, much more expensive."

Still, with regard to the cost of nirsevimab, Long did not hold back her frustration with the manufacturer, Sanofi, which said it anticipates pricing the drug at $495 per dose in the commercial market and $395 per dose in the CDC's program, which provides no-cost vaccines for eligible children via enrolled physicians using federal funds. (ACIP voted unanimously during the meeting to have the monoclonal antibody covered by the program.)

"We are extraordinarily disappointed with the price setting of the manufacturer," she said, adding that if a maternal vaccine is licensed, ACIP will then "address the use of this product, as well as that licensed product, should that come to fore."

In discussion, ACIP Chair Grace Lee, MD, MPH, a pediatrician at Stanford University School of Medicine in California, also spoke directly to insurers, saying that hospitals and family physicians having to pay up front for the drug without knowing whether they will be reimbursed will impact vaccine availability.

"This is a plea generally to ask for a reconsideration of where the risk is actually laid, because right now it is a huge cost and, honestly, a disincentive to be able to get people to do the right thing," Lee said.

The FDA on July 17 approved nirsevimab for all infants and high-risk children under 2 years of age for preventing RSV-related lower respiratory tract infections. In trials, the monoclonal antibody lower respiratory tract infection by between 70-75%.

The most common adverse events seen with nirsevimab included rash and injection site reactions. The FDA also flagged the potential for serious hypersensitivity reactions, including anaphylaxis, which has been observed with other immunoglobulin G1 monoclonal antibodies.

The agency also warned that the drug "should be given with caution to infants and children with clinically significant bleeding disorders."

In the U.S., RSV usually begins circulating in the fall and peaks in the winter months, although the pandemic has altered trends in this and other illnesses. Administration of the therapeutic is recommended from October through March; however, providers should defer to local epidemiologists on timing due to seasonality differences in different parts of the country.

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