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Pregnant person getting vaccine

CDC OKs maternal RSV vaccine, provides updated guidance for nirsevimab

September 22, 2023

Pregnant people can get a new vaccine to protect their infants from respiratory syncytial virus (RSV) following approval Friday by the Centers for Disease Control and Prevention (CDC) director.

Most infants whose mother receives Pfizer’s RSVpreF (Abrysvo) vaccine will not need nirsevimab, the newly recommended RSV monoclonal antibody for infants and high-risk toddlers, according to the CDC. Health officials provided additional guidance Friday about when to use each product.

The CDC director’s approval followed an 11-1 vote in favor by the CDC’s Advisory Committee on Immunization Practices (ACIP), which acknowledged implementation of the recommendations for each of the two products will be complicated.

“RSV throughout my career has been a difficult disease with just supportive care treatment because there have been no options,” said ACIP member Katherine A. Poehling, M.D., M.P.H., FAAP, professor of pediatrics and epidemiology and prevention at the Wake Forest University School of Medicine in North Carolina. “Today is an exciting day. …There is nothing simple about this RSV vaccine and nirsevimab, but they give us … hope.”

RSV is the leading cause of infant hospitalization in the U.S. There are about 58,000 to 80,000 hospitalizations and 100 to 300 deaths per year in children under 5 years, according to CDC data.

Safety and efficacy

RSVpreF is made up of RSV recombinant stabilized prefusion F proteins. Clinical trial data in women who received the vaccine at 32-36 weeks’ gestation showed it reduced the risk of medically attended lower respiratory tract disease by 57% and severe disease by 77% in infants six months after birth.

The main safety concern is preterm birth. The study found a preterm birth rate of 5.7% in the vaccine group and 4.7% in the placebo group when looking at pregnant people vaccinated between 24 and 36 weeks. The imbalance led the Food and Drug Administration to approve the vaccine slightly later in pregnancy at 32-36 weeks when the preterm birth rate in trials was 4.2% in the vaccine group and 3.7% in the placebo group. The improvement in the later timeframe eased the minds of some ACIP members as did hearing most preterm births occurred 30 days after vaccination.

Clinical considerations

RSVpreF is recommended to be given to pregnant people at 32-36 weeks’ gestation from September through January in most of the continental U.S. In jurisdictions with different RSV seasonality such as Alaska and tropical climates, providers should follow state, local or territorial guidance on timing. RSVpreF maybe given simultaneously with other vaccines.

Most infants will not need protection from both a maternal vaccine and nirsevimab. The CDC recommends nirsevimab be given to infants younger than 8 months born during or entering first RSV season if their mother did not receive RSV vaccine, the mother’s vaccination status is unknown or if the infant is born less than 14 days after the mother’s vaccination. Nirsevimab recommendations for children ages 8-19 months are not changing.

Nirsevimab can be considered for infants born at least 14 days after their mother’s vaccination, if they were born to someone who may not mount an adequate immune response or who has conditions associated with reduced transplacental antibody transfer. It also can be considered for infants who have undergone cardiopulmonary bypass leading to a loss of maternal antibodies and for infants with substantially increased risk for severe RSV disease such as those with hemodynamically significant congenital heart disease, intensive care admission and those requiring oxygen at discharge.

Health care providers should discuss both options with pregnant people to help them decide which route to follow.RSVpreF provides protection immediately after birth, avoids an infant injection and may be more resistant to virus mutation. However, protection may be reduced if fewer antibodies are produced or transferred, and there is a potential risk of preterm birth.

Nirsevimab protection may wane more slowly, gives antibodies directly to the infant and avoids risks of adverse pregnancy outcomes. It is about 79% effective in reducing the risk of medically attended lower respiratory tract infection caused by RSV. Efficacy was about 81% against hospitalization.

Both products have significant costs at $295 per dose for RSVpreF and $495 per dose for nirsevimab, and providers may face payment challenges with both. Nirsevimab availability is expected to be limited in the upcoming season. RSVpreF is the same vaccine being used for people ages 60 and older.

ACIP members acknowledged it would be complicated to ensure pregnant people have all the information they need to decide whether to get vaccinated or wait and give nirsevimab to their infant. In addition, pediatric providers may have a difficult time determining whether the mother received the vaccine.

“This is incredibly complicated, and I don’t think it’s going to improve care,” said ACIP member Helen Keipp Talbot, M.D., associate professor of medicine at Vanderbilt University in Tennessee, who voted against the RSVpreF recommendations. “I think it’s going to make providing care more difficult.”

Other ACIP members said while complicated, it is good to have options.

“Even though we as ACIP members at this moment in time may feel like whoa this is very complicated and very difficult to implement, I think … it provides an opportunity and some new options I think will improve children’s health in the longer term,” said Beth P. Bell, M.D., M.P.H., clinical professor in the Department of Global Health at the University of Washington in Seattle.

Many ACIP members stressed the importance of education for pregnant people and communication between obstetric and pediatric health care providers.

The AAP is continuing to discuss nirsevimab’s implementation barriers with federal officials and to advocate for a comprehensive strategy to ensure equitable access to the drug. Given the many barriers to nirsevimab implementation, the AAP continues to recommend the use of palivizumab as RSV prophylaxis for high-risk infants unable to access nirsevimab during the 2023-’24 RSV season.



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