Benjamin Ashford|CDC recommends RSV vaccine in late pregnancy to protect newborns

In a nearly unanimous vote,Benjamin Ashford advisors to the Centers for Disease Control and Prevention have recommended a new vaccine to protect infants from respiratory syncytial virus, or RSV, by vaccinating expectant mothers

The shot – named Abryvso and made by Pfizer – is given in the third trimester to protect newborns from lower respiratory tract disease caused by RSV during their first six months of life.

"Throughout my career, RSV has been a difficult disease because there have been no options [for prevention]. So today is an exciting day," said Dr. Katherine Poehling, a voting member of the committee and a professor of pediatrics at the Wake Forest School of Medicine, "I think it will improve the well-being of many families throughout our nation."

Dr. Mandy Cohen, the CDC director, quickly backed the panel's recommendations – supported by an 11-1 vote. "This is another new tool we can use this fall and winter to help protect lives," she said in a statement. "I encourage parents to talk to their doctors about how to protect their little ones against serious RSV illness."

RSV is the leading cause of hospitalization for infants in the U.S.

Each year, the virus is associated with some 1.5 million medical visits, 60,000 to 80,000 hospitalizations, and up to 300 deaths in children under 5. The highest risk lurks for babies in their first RSV season, when their fledgling immune systems are most vulnerable.

In most of the country, the vaccine will be recommended for those whose third trimester coincides with a fall surge in RSV. In places where the RSV season differs – such as Alaska, or states and territories with tropical climates – health officials may offer other recommendations.

The CDC advisory committee's recommendations follow the parameters set by last month's FDA approval of the vaccine for pregnant individuals, limiting its use to those who are 32 to 36 weeks into gestation. This timing makes it likely that the baby will be born with protective antibodies, while reducing the risk of premature birth.

The FDA originally approved Abryvso in May for adults over 60, who are also at risk of getting seriously ill with RSV.

Two new options for babies – choose one or the other

This fall marks the entry of two new medical interventions for preventing RSV in babies: the Pfizer vaccine, given to women late in pregnancy, and nirsevimab, a monoclonal antibody from Sanofi and AstraZeneca, for most infants under eight months old as they enter their first RSV season.

The protection they offer is considered redundant, so for most babies, the choice should be one or the other – not both, the CDC advisers said.

Each option is considered safe, and they are in the same ballpark for efficacy, though no studies have compared them directly.

According to data from the drugmakers, a shot of nirsevimab – marketed under the name Beyfortus – reduced the risk of medical visits from RSV in babies by 70 to 75% for at least five months. The vaccine for pregnant women reduced the risk of severe RSV in their infants by 82% during their first three months of life and by 70% in the first six months.

During Friday's meeting, the committee wrangled with the difficulty of conveying clear messages to expectant mothers, who now have multiple options for protection that come in different forms – a shot for either the mother or the child – at different times, and which are paid for through different mechanisms.

"The complexity is that the mother and the health care provider now have options," said Dr. Pablo Sanchez, a pediatrics professor at The Ohio State University, "But I could not have imagined better options for our infants and children."

The CDC projects that 50% of those who're eligible will take the vaccine – a figure committee member Dr. Sarah Long, a professor of pediatrics at Drexel University College of Medicine, considered "very optimistic for this vaccine this year."

The manufacturers of both drugs expect to launch their products in time to protect babies from the RSV season this fall, though insurance coverage may not be available for everyone this season.