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New RSV drug for infants in short supply, just months after landmark approval

Touted as ‘lifesaving,’ the drug reduces the risk of hospitalizations and health care visits by about 80 percent.

Uncredited/Associated Press

Just two months after public health authorities touted it as a “lifesaver” and a “powerful new tool to protect infants,” a new medication to treat respiratory syncytial virus in very young children is in short supply.

There won’t be enough of the drug to protect all infants, the Centers for Disease Control and Prevention warned health providers Monday afternoon, advising pediatricians to reserve certain doses for the most high-risk babies and to urge women in their last trimester of pregnancy to receive new RSV vaccines that would help protect their newborns.

Sanofi, the drug’s developer, blamed the shortage on higher than expected demand and said it was working to boost supply and to ensure equitable distribution. A Massachusetts official said the state expects to see shipments of one of the two types of dosages of the treatment to resume in about a month.


While anyone can contract RSV, it poses the greatest risk to infants and the elderly. Virtually every child becomes infected before age 2, and in infants the virus tends to settle in the lungs. Even babies with no underlying health problems can get sick enough to need a doctor’s visit, a trip to the emergency room, hospitalization, and sometimes intensive care, said Dr. Mary Beth Miotto, president of the Massachusetts chapter of the American Academy of Pediatrics. Each year, an estimated 58,000 to 80,000 children under age 5, most of them infants, are hospitalized with RSV infections, with some requiring oxygen, intravenous fluids, or mechanical ventilation, according to the CDC. An estimated 100 to 300 children younger than 5 die.

“It is not a mild cold. It is probably one of the worst respiratory infections we get in our lifetime when we get it that young,” Miotto said.

That’s why nirsevimab, also known as Beyfortus by its developers, was greeted with such enthusiasm by pediatricians, parents, and public health experts when the FDA approved it in July. This season was to mark the first time a preventive medication was available to all babies.


“It was very disappointing to hear about the supply chain problem,” Miotto said, but she considers it “a forced timeout” during which hospitals and medical practices can perfect the rollout of a new product that doctors and patients need time to understand.

“This is a marathon,” she said. “There’s always bumps in the road.”

Because the drug is newly available and distribution is barely underway, Dr. Aaron D. Bornstein, of Middleboro Pediatrics in Lakeville, said many parents may not even be aware of it.

“It’s still not in the public consciousness — it’s not like I’ve had families come in and ask for it,” said Bornstein. “It’s not like we’re pulling back on something we promised.”

In August, the CDC recommended that all infants under 8 months receive nirsevimab for their first RSV season. High-risk children between 8 months to 19 months, including those with chronic lung disease or who are immunocompromised, should also receive it. Children who weigh less than around 11 pounds receive a 50-milligram injection; those who weigh more receive 100 milligrams. The 100-milligram doses are in particularly short supply.

The medication, a monoclonal antibody, provides babies with synthetic antibodies designed to help them fight off disease. Vaccines, by contrast, teach the body to make its own antibodies. In clinical trials, nirsevimab reduced the risk of hospitalization and health care visits by about 80 percent.


“Based on manufacturing capacity and currently available stock, there are not sufficient 100 mg dose prefilled syringes of nirsevimab to protect all eligible infants weighing ≥5 kg during the current RSV season,” the CDC said in its advisory. “Additionally, supply of the 50mg dose prefilled syringes may be limited during the current RSV season.”

Sanofi attributed the shortage to unexpectedly high demand.

“Despite an aggressive supply plan built to outperform past pediatric vaccine launches, demand for this product, especially for the 100 mg doses used primarily for babies born before the RSV season, has been higher than anticipated,” Sanofi said in a statement on its website. It pledged to work to equitably distribute remaining doses and to work with its manufacturer to accelerate and boost supplies.

“It’s not an uncommon situation,” Dr. Rick Malley, senior physician in infectious disease at Boston Children’s Hospital, said of the shortage, because with a new product, drugmakers often have difficulty predicting demand.

Dr. Estevan Garcia, a pediatrician and chief medical officer at the state Department of Public Health, said he expects shipments of 50-milligram doses to become available in about a month, and the state will prioritize distribution of the drug to birthing hospitals to give injections to newborns. Even though nirsevimab is not technically a vaccine, the state made arrangements to purchase the drug through its childhood immunization program, which supplies vaccines for free to medical practices. The state has so far received 6,275 100-milligram doses and 5,795 50-milligram doses of nirsevimab.


Children at highest risk of severe effects will get first dibs on nirsevimab. They also will continue to have access to palivizumab, a similar monoclonal antibody intended for high risk babies including, he said. But palivizumab doesn’t last long and children need to get a new dose every month, while nirsevimab offers protection for the entire season.

In its alert, the CDC offered guidance for how to stretch supplies and reserve doses for those at highest risk. Among the CDC’s recommendations: Providers should encourage pregnant people to receive Abrysvo, a new RSV vaccine from Pfizer, between 32 weeks through 36 weeks and 6 days of pregnancy to prevent RSV in their newborns. Infants whose moms receive Abrysvo don’t need nirsevimab.

“The good news is, there’s interest, lots of interest across the state,” Garcia said.

With the doses distributed so far, plus the pregnant women who get vaccinated with Abrysvo, Garcia expects to see less severe illness even in the upcoming season. “I think we will see some protection out there in the community,” he said.

Current reports to the National Respiratory and Enteric Virus Surveillance System (NREVSS), a national laboratory-based surveillance network, indicate RSV transmission has increased to seasonal epidemic levels in the Southern regions of the United States and is expected to continue to increase in the rest of the country within the next one to two months.

Felice J. Freyer can be reached at felice.freyer@globe.com. Follow her @felicejfreyer. Anna Kuchment can be reached at anna.kuchment@globe.com. Follow her @akuchment.