Another Big First in RSV Protection

US regulators on Monday approved the first RSV vaccine for pregnant women so their babies will be born with protection against the scary respiratory infection, the AP reports. RSV is notorious for filling hospitals with wheezing babies every fall and winter. The Food and Drug Administration cleared Pfizer's maternal vaccination to guard against a severe case of RSV when babies are most vulnerable—from birth through 6 months of age. The next step: The Centers for Disease Control and Prevention must issue recommendations for using the vaccine, named Abrysvo, during pregnancy. (Vaccinations for older adults, also at high risk, are getting underway this fall using the same Pfizer shot plus another from competitor GSK.)

"Maternal vaccination is an incredible way to protect the infants," said Dr. Elizabeth Schlaudecker of Cincinnati Children's Hospital, a researcher in Pfizer's international study of the vaccine. If shots begin soon, "I do think we could see an impact for this RSV season." How the RSV vaccination will work: A single injection late in pregnancy gives enough time for the mom-to-be to develop virus-fighting antibodies that pass through the placenta to the fetus—ready to work at birth. It's the same way pregnant women pass along protection against other infections. Pregnant women have long been urged to get a flu shot and a whooping cough vaccine—and more recently, COVID-19 vaccination.

Pfizer's study included nearly 7,400 pregnant women plus their babies. Maternal vaccination didn't prevent mild RSV infection—but it proved 82% effective at preventing a severe case during babies' first three months of life. At age 6 months, it still was proving 69% effective against severe illness. Vaccine reactions were mostly injection-site pain and fatigue. In the study, there was a slight difference in premature birth—just a few weeks early—between vaccinated moms and those given a dummy shot, something Pfizer has said was due to chance. The FDA said to avoid the possibility, the vaccine should be given only between 32 weeks and 36 weeks of pregnancy, a few weeks later than during the clinical trial. (The only other option to guard babies from RSV: Giving them lab-made antibodies.)