Only 56% of US infants are protected by RSV vaccine and antibodies

Last year, for the first time, the United States had two approved methods to combat respiratory syncytial virus (RSV) infections in infants: a maternal vaccine, given in the final weeks of pregnancy, and the antibody nirsevimab, which RSV is administered to infants under 8 months of age during the season.

But In Weekly report on morbidity and mortality, Authors describe Results from a Centers for Disease Control and Prevention (CDC) survey show that only 55.8% of infants were protected by the maternal RSV vaccine, nirsevimab, or both.

To evaluate the use of maternal vaccine and infant antibodies, CDC conducted a web-based survey from March 26 to April 11, 2024, among women ages 18 to 49 years who reported becoming pregnant at any time since August 1, 2023 be.

The survey included 866 women with an infant born between August 2023 and March 2024; The RSV vaccination rate analysis was limited to 678 women who were 32 to 36 weeks pregnant between September 1, 2023 and January 31, 2024.

NInfant irsevimab coverage and the proportion of infants protected by either maternal or infant immunization were evaluated in 866 women who had a live birth between August 1, 2023 and March 31, 2024.

The provider's recommendation had a major influence on acceptance

The RSV vaccination rate among mothers was 32.6%, and of these, 54.1% reported receiving the vaccine in an obstetrician-gynecologist's office. Several factors are associated with maternal vaccination, the authors said. Utilization was higher among those with private or military insurance (38.9%) than among those with public insurance (28.0%); those living at or above the poverty line (35.0%) compared to those living below the poverty line (26.4%); and those with more than a college degree (50.1%) than those with a college degree or less (28.7%–32.7%).

Notably, only 1.9% of women who did not receive a medical recommendation received the vaccine, compared to 56.7% of those who relied on a provider recommendation.

“Approximately half of pregnant women did not report receiving a physician recommendation for maternal RSV vaccination or nirsevimab for their infants, suggesting that they missed opportunities to protect infants from severe RSV disease.” , write the authors.

Nirsevimab infant coverage was 44.6%. Again, utilization was higher among those who received a provider recommendation for maternal or child RSV vaccination (58.7%) compared with those who did not receive a recommendation (28.3%).

Overall, 55.8% of infants were protected by either maternal RSV vaccination, nirsevimab, or both; 14.2% of infants were protected by both. These numbers were below projected percentages.

Several challenges in rolling out the new vaccine products may have resulted in lower vaccination coverage than expected.

“Several challenges in the introduction of the new vaccination products may have resulted in a lower than expected vaccination rate,” the authors write. “These challenges included the timing of recommendations and product availability, varying recommendations regarding the timing of vaccine and nirsevimab administration… and concerns about the safety and effectiveness of the products.”

Antiviral treatment shows promising results

In the corresponding RSV research promising resultResults from a phase 3 randomized, placebo-controlled trial conducted in China show that ziresovir, a novel antiviral treatment for RSV, significantly reduced viral load and clinical outcomes in bronchiolitis on day 3.

The study, published in the New England Journal of MedicineThese included 244 children and toddlers who were hospitalized with RSV.

No safety concerns were identified.

“These initial results warrant further evaluation in an international phase 3 study of ziresovir for the treatment of RSV infections,” the authors concluded.