Some pregnant women and babies received the wrong RSV shots

This winter, for the first time, two vaccines were available to ward off respiratory syncytial virus, which is especially dangerous for older adults and infants. Only one of them – Abrysvo, made by Pfizer – was approved for pregnant womenand neither was for young children.

The distinction has apparently been missed by some doctors and pharmacists.

At least 128 pregnant women accidentally received the alternative vaccine – Arexvy, from GSK – and at least 25 children under the age of 2 received a shot, the Centers for Disease Control and Prevention announced. warned.

Dr. Sarah Long, a pediatric infectious disease doctor and adviser to the agency, said she was “blindsided” by the reports. “It's very disturbing that this has to happen,” she said.

Arexvy has not been tested in pregnant women or children, so information about its effects in these groups is limited. No serious damage from the errors has yet been confirmed, but in most reported cases the outcome was unknown.

Based on the available data, Dr. Long said she was more concerned about the young children who received an RSV vaccine than about the pregnant women who received Arexvy or their babies. Evidence from animal testing “strongly suggests” that Arexvy could worsen, rather than alleviate, RSV infection in children under 2 years of age. according to the Food and Drug Administration.

To prevent that, the CDC has recommended that children who accidentally receive either vaccine also receive nirsevimab (sold as Beyfortus), a monoclonal antibody that causes strong immune protectionas long as the RSV season lasts.

Up to 80,000 children In the United States, children under age 5 are hospitalized with RSV infections every year, and the virus is one of the leading causes of death among children worldwide.

In 2022, GSK halted clinical trials of a version of its vaccine in pregnant women after a safety study found there was an increased risk of premature birth. The company also noted an increase in neonatal deaths, but said these were a result of premature birth.

GSK is still monitoring participants in those studies and sharing the data with the FDA, said Alison Hunt, a company spokeswoman.

In the Pfizer study, Abrysvo also showed a slightly higher risk of preterm birth up to 37 weeks' gestation, but the increase was not statistically significant.

Still, concerned about the potential risk of premature birth, the FDA only approved Abrysvo for pregnant women between 32 and 36 weeks of gestation. (The goal is to produce antibodies in women that can be passed on to babies, protecting them immediately after birth.)

CDC advisors further narrowed the window by recommending the vaccinations only for pregnant women September to Januaryaimed at protecting babies born during peak RSV season.

“In reviewing the data, we felt somewhat conservative,” said Dr. Camille Kotton, a physician at Massachusetts General Hospital and one of the agency's scientific advisers.

“If there were a problem with preterm birth, delivery in the last eight weeks of pregnancy would probably have less impact than earlier in pregnancy,” she said.

Some babies who accidentally received an RSV vaccine were meant to receive nirsevimab. The GSK vaccine appears to have been given to some pregnant women because Pfizer's vaccine was not as widely available and pharmacists thought they were interchangeable.

Amy Gardner, 39, a former kindergarten teacher in Cleveland, Tennessee, said she tried to find Pfizer's RSV vaccine for her pregnant daughter at several pharmacies. In mid-September, on the very last day her daughter was eligible for the shot, she found a drugstore that said the vaccine was in stock, Ms. Gardner said.

But her daughter got Arexvy instead.

“We are all human, but there needs to be more checks and balances than this,” Ms Gardner said. She believes the shot led to her daughter's premature delivery a few hours later.

The errors were reported to a federal database called the Vaccine Adverse Event Reporting System. Those administering the vaccines may have been confused in part by the similarity of the two names, experts said.

“It's just terrible – why, why did they do this?” said dr. Lung. “A lot of people got paid a lot of money to come up with these names, and I don't understand them.”

Dr. Kotton urged the FDA to encourage companies to give similar products clearly distinguishable names. “If vaccines come out at the same time, it would probably be good to have different names where possible,” she said.

Dr. Long said she was stunned that young children were receiving RSV vaccines. Because they are not approved for children, pediatric practices, which typically administer vaccines, should not have stocked any.

“It's important to find out how that happened because we don't want this to happen again,” she said.