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FDA panel recommends injectable drug to prevent RSV in infants

The monoclonal antibody shot would be given to babies during or before their first RSV seasons, as well as to high-risk children up to age 2 entering their second RSV seasons.

An independent advisory committee to the Food and Drug Administration voted Thursday to recommend an injectable drug that can protect infants up to 2 years old from RSV.

The 21-person panel voted unanimously to recommend the shot for newborns and infants during their first months of exposure to RSV. The group also voted 19-2 in favor of giving second doses to children up to age 2 who are vulnerable to severe infections — such as those with chronic heart or lung disease — during their second RSV seasons.

The FDA must now decide whether to approve the injection; it is likely to follow the committee’s recommendation.

Respiratory syncytial virus causes lower respiratory illness and is most severe for older adults and babies under 6 months old. Among children under 5, the virus leads to up to 80,000 hospitalizations and up to 300 deaths a year in the U.S. Most people are infected by age 2.

The monoclonal antibody drug being considered is administered as a single injection, and it functions similarly to a vaccine. But instead of prompting the immune system to develop antibodies to the virus, it delivers the antibodies directly to the bloodstream. Scientists refer to that as passive immunization. Monoclonal antibodies were also used to treat Covid before new variants of the coronavirus rendered them ineffective.

“It’s a temporary shield, whereas when there’s active immunization you have memory immunity that can be called to the rescue months or years later,” said Dr. Ofer Levy, the director of the Precision Vaccines Program at Boston Children’s Hospital, who wasn't involved in Thursday’s vote.

“Active immunization” refers to the protection from vaccines, but no RSV vaccine for infants has been approved.

The new monoclonal antibody drug, called nirsevimab and sold under the name Beyfortus, is already approved in Europe, Canada and the United Kingdom. It was developed by the pharmaceutical giant AstraZeneca in partnership with Sanofi. 

In a study of nearly 1,500 infants, the shot lowered the risk of developing respiratory disease from RSV that required a doctor's visit by nearly 75% for at least five months.

In a study of more than 1,400 infants born prematurely — a group at particular risk — the injection was found to lower the risk of developing respiratory disease from RSV that required doctors’ visits by around 70% for at least five months. It lowered the risk of hospitalization from RSV by around 78% during that time.

“The studies as presented showed clear evidence of efficacy and reassuring evidence of safety across all the subgroups presented, and I think that this could be a real game changer,” said a member of the FDA panel, Dr. George Siberry, a medical officer at the U.S. Agency for International Development.

Sally Hunsberger, a biostatistician at the National Institutes of Health, was one of the two committee members who voted not to recommend the injection for high-risk children up to age 2.

“It’s a bit of a weak ‘no,’ but hopefully that will just emphasize that I feel like we do need more data,” Hunsberger said.

RSV infection rates typically rise in the fall and peak in the winter. However, last year's season started in June and peaked in November, and it resulted in a dramatic spike in severe illnesses that overwhelmed children's hospitals.

AstraZeneca said Thursday that if its drug gets approved, infants born from April to October could get immunized at their pediatricians’ offices before the coming RSV season. Infants born from November to March could get immunized after birth, before they leave the hospital.

The company estimated that its injection could prevent up to 500,000 medical visits a year, including up to 60,000 hospital admissions.

In a briefing document, the FDA determined that the injection was safe based on the results of three trials with a total of more than 3,600 participants. A small minority of healthy and preterm infants vaccinated during their first RSV seasons developed rashes as a side effect. Some infants at high risk of severe RSV developed fevers.

The FDA noted that there were more overall deaths among babies who received the shot compared to those who received placebos or different antibody injections, but it determined that the discrepancy most likely wasn't related to AstraZeneca’s drug.

The company said Thursday that it should be safe to administer the injection alongside routine childhood vaccinations, such as flu shots.

The FDA has already approved one monoclonal antibody injection to protect infants from RSV: a drug called Synagis. But it is approved only for high-risk infants and must be administered monthly during RSV season. The drug lowered the risk of hospitalization from RSV by 45% to 55% in trials.

A vaccine administered to pregnant mothers to protect infants from RSV may also get approved soon: FDA advisers voted last month to recommend the shot. The vaccine, made by Pfizer, lowered the risk of severe disease from RSV among infants by 82% within roughly three months of birth. By around six months, efficacy was around 69%.

The FDA said Thursday that it was unsure whether infants who already had protection from Pfizer's shot would get an added benefit or whether there would be new safety concerns if they also got AstraZeneca’s injection.

The FDA approved the world’s first RSV vaccine, for adults ages 60 and up, in early May. Then, last week, it approved a second vaccine for older adults, which is made by Pfizer and is the same formulation that could be given to pregnant people.