(The Hill) — A supply shortage means a drug that can prevent respiratory syncytial virus (RSV) in infants won’t have a major immediate impact, children’s hospitals said, and they are preparing for a surge in admissions this respiratory disease season.

“Widespread access [to the new antibody drug] will take time across many sectors of the pediatric population and won’t have as great an impact on volumes this immediate respiratory season,” the Children’s Hospital Association said in a statement.

Nirsevimab, marketed as Beyfortus, was approved in August. It’s a single shot that can be given to infants up to 8 months old, and high-risk babies up to 19 months old. 

The drug is a monoclonal antibody, rather than a traditional vaccine, meaning babies will be able to directly receive antibodies to prevent severe RSV disease, rather than prompting the immune system to develop them. It cuts the risk of hospitalizations in infants by about 80 percent and has been hailed as a game changer.

Those include American Indian and Alaska Native children younger than 8 months who live in remote areas, as well as infants born before 29 weeks of gestation and those who are severely immunocompromised.

But the Centers for Disease Control and Prevention (CDC) last week urged pediatricians to ration the drug due to supply constraints and prioritize infants at highest risk of complications. 

The agency’s Vaccines for Children program, which covers the cost of the shots for uninsured and underinsured kids, paused orders for the 100-milligram dose earlier this month. The 100mg dose is recommended for babies 11 pounds and over until they’re 8 months old.

The agency only recently resumed orders for the 50-milligram dose for babies who weigh less than 11 pounds. Sanofi said it was temporarily not accepting new orders for 100-milligram doses but is fulfilling current deliveries.

According to Sanofi, which markets the drug, demand has been much higher than anticipated, and it is working with manufacturer AstraZeneca to deliver available doses quickly. 

A Sanofi spokesman told The Hill the company did not have any updates.

Drug shortage experts said they’re puzzled.

Unlike other generic drugs, there aren’t any known manufacturing disruptions or shortages of raw materials needed to make the drug. The manufacturer just underestimated demand.

“I’m not sure what market research they did, but it’s fairly easy to look at statistics on how many births are a year and to know the timing … I think it’d be reasonable to use those statistics to understand what the demand is,” said Mike Ganio, senior director of pharmacy practice and quality at the American Society for Health-System Pharmacists.

“Hopefully, this shortage doesn’t lead to another kind of surge in respiratory infections over the winter,” Ganio said. 

In its October update, CDC said it “continues to anticipate that the upcoming fall and winter respiratory disease season will likely result in a similar number of hospitalizations as last season,” which will be more than in seasons before the pandemic. 

Current RSV levels are low nationally, but “sustained increases in RSV activity in the southern U.S. indicate the start of the 2023-2024 RSV season, with the mid-Atlantic and Northeastern regions also now experiencing elevated activity,” CDC said.

Last year saw scores of young children infected by RSV much earlier than in past years, overwhelming children’s hospitals and emergency rooms across the country. 

“Children’s hospitals are working with community hospitals and other health systems to help manage pediatric beds, equipment and medicine supplies as well as pediatric workforce staffing, but undoubtedly there will be capacity challenges this fall and winter,” Children’s Hospital Association CEO Matt Cook said in a statement.

Prior to this year, there’s never been a drug that can prevent RSV in all infants. But it wasn’t approved by federal regulators until late summer, and public health experts and pediatricians have questioned the wisdom of such a condensed timeline in making sure there were enough doses on the market before the start of RSV season.

Early rollout of the shot has also been marred by a lack of insurance coverage.

Pediatricians often have to buy the drug directly from suppliers or the manufacturer, and it costs $495 per dose in the private sector. According to pediatricians, it’s unclear if insurance companies will reimburse them for buying and administering it. 

The federally funded Vaccines for Children program pays $395 per dose.

Sanofi said that as of October 1, coverage is in place for more than 90 percent of infant lives.

The company is also offering extended payment terms for doctors who purchase directly from Sanofi, meaning providers can order and receive Beyfortus to administer right away but they don’t have to pay back Sanofi until later this year, towards the end of RSV season.

In the meantime, the CDC advised expectant parents to consider a new maternal RSV vaccine Abrysvo, which is recommended for pregnant people to confer protection to newborns through their first 6 months of life. But it can only be administered in weeks 32 through 36 of pregnancy.

Joseph Choi contributed.