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August 22, 2023

RSV vaccine for babies, given to their mothers during pregnancy, receives FDA approval

Abrysvo reduced the risk of lower respiratory tract illnesses, like pneumonia, by nearly 82% within infants' first 3 months of life, a clinical trial found

A vaccine that protects infants from respiratory syntactical virus, known as RSV, has been approved by the U.S. Food and Drug Administration. 

Abrysvo is a single-dose shot that can be given to expectant mothers during the 32nd and 36th weeks of pregnancy. The vaccine, developed by Pfizer, spurs production of antibodies that are transferred from the mother to the baby in the placenta. It offers protection against RSV through the baby's first six months of life. 

RSV is common respiratory illness that typically causes mild, cold-like symptoms. Most children get RSV by the time they turn 2 years old, but they are at greater risk of experiencing severe complications like bronchiolitis and pneumonia. Up to 3% of infants under 12 months become hospitalized with RSV, according to the American Academy of Pediatrics. Older adults also are at increased risk for severe RSV illnesses.

In most parts of the U.S., RSV begins circulating during the fall and peaks in the winter. But last year, RSV cases began mounting in the summer. By the fall, hospitals were filling up, with doctors saying the surge was the worst they had seen in years. 

About 4 out of every 1,000 babies under 6 months had been hospitalized with RSV by November, as had more than 2 of every 1,000 babies ages 6-12 months. Those rates are not typically seen until the seasonal peak in December. 

This year, the first RSV vaccines for older adults – Alexvy and Abrysvo – already are available. So is Beyfortus, a new injectable drug designed to protect children under 2. Now, the Abrysvo vaccine will be made available to pregnant people once the U.S. Centers for Disease Control and Prevention issues a recommendation and Director Dr. Mandy K. Cohen signs off on it.

"RSV is a common cause of illness in children, and infants are among those at highest risk for severe disease, which can lead to hospitalization," said Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research. "This approval provides an option for health care providers and pregnant individuals to protect infants from potentially life-threatening disease." 

A clinical trial of 7,000 people found Abrysvo reduced infants' risk of severe lower respiratory tract illnesses by 81.8% within their first three months of life, and by 69.4% within sixth months. 

The most commonly reported side effects in pregnant people who received Abrysvo were pain at the injection site, headache, muscle pain and nausea. Preeclampsia, a dangerous hypertensive disorder, was slightly more common among people who received the vaccine, though it was not commonly reported. Also, babies born to vaccinated mothers were more likely to have a low birth weight or jaundice. 

There is not enough evidence to indicate the vaccine causes preterm births, but its label includes a warning about the imbalance in preterm births, and health care providers are advised not to administer the vaccine before the 32nd week of pregnancy. 

The FDA is requiring Pfizer to conduct more studies to evaluate the risk of preterm birth and preeclampsia in vaccine recipients. 

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