Neonates are greatly susceptible to contracting RSV and developing severe disease in the earliest stages of life.

“They get bronchiolitis, they get pneumonia, and they’re hospitalized when they have trouble breathing and they need oxygen support,” said Helen Chu, MD, MPH, professor of Medicine, Epidemiology, and Global Health at the University of Washington. “For the last several decades, the number 1 cause of hospitalizations of infants in the United States was RSV infection. So it is a significant burden, both on the parents and the caregivers of these infants, and also on the healthcare system.”

At ID Week 2024, Chu participated in a symposium, A Whole New World? Respiratory Syncytial Virus in the Vaccine and Monoclonal Antibody Era. Later that same day, she sat down with Contagion to discuss some of the nuances between the maternal vaccine and monoclonal antibody.

In the last few years, there has been significant development in this area. And currently, there is 1 monoclonal antibody (nirsevimab-alip (Beyfortus), Sanofi/Astra Zeneca) and 1 maternal RSV vaccine (Abrysvo, Pfizer) that are both FDA approved to prevent lower respiratory tract disease in neonates.

“Both the maternal vaccine and the monoclonal antibody are designed to protect the infant in the first few months of life, specifically protecting against severe disease that requires hospitalization, and they are both highly effective in doing that,” Chu said. “In the clinical trials of the maternal vaccine, the efficacy against RSV hospitalization was around 60% to 70%. That number was very similar for the monoclonal antibody that’s given at birth to infants, also 60 to 70%, in the clinical trials. We now actually have more data from this first season, because both products are out, and it seems as though the monoclonal antibody is still looking like that out in the community. In studies from Europe, the effectiveness of the monoclonal antibody is 70% against hospitalization. So, if you think about that, it’s really the number of hospitalizations of infants in Europe has gone down dramatically because of receipt of nirsevimab.“

While there is great protection afforded both immunizations, she points out to some of the nuances between the 2 for delivery.

“The maternal vaccine is given during pregnancy. Right now, the recommendation in the United States is to give it between 32 and 36 weeks gestation, and the idea is then it protects the baby through antibody that’s transferred across the placenta, and then the antibody stays in the baby system for the first 4 to 6 months after birth,” Chu said. “This is different from the monoclonal antibody, nirsevimab, which is given when the baby is born, and then directly administered to the baby, and it also lasts 4 to 6 months.”

“In terms of logistics, I think there’s a couple of things that are challenging. First of all, the maternal vaccine has to be given during this very narrow gestational window—32 to 36 weeks in your OB’s office. So that is hard to do. Uptake was quite low—below 20% for nirsivimab. There have also been a lot of challenges, mostly related to the fact that you really need to give it very early in life to protect the infant, because they get very sick at a very young age, and being able to get it during the birth of the infant before they get discharged would be the best way to do that, but it’s a very expensive product, and right now, the reimbursement isn’t worked out.”

To learn more about RSV vaccines and monoclonal antibodies, check out our roundtable on the subject.