The Federal Drug Administration on Monday approved a vaccine called Abrysvo that’s meant to protect infants against respiratory syncytial virus.

Expectant mothers take the vaccine to protect the child in gestation from the dangerous respiratory infection. RSV is most common in fall and winter, with infants most at risk from birth to 6 months of age. It’s the first maternal RSV drug approved by the FDA.

How effective is the drug? A Pfizer study of 7,400 women showed 82 percent effectiveness for protecting against severe RSV cases for infants up to three months after birth, and 69 percent effective in infants up to 6 months. Women are advised to take the vaccine in their last trimester for best results.

Maternal vaccines are already available for other viruses, including the flu and COVID-19.

This story originally appeared in WORLD. © 2023, reprinted with permission. All rights reserved.