RSV prevention shows high efficacy despite emerging antibody resistance

Recent medical data highlights both the efficacy and emerging challenges in preventing Respiratory Syncytial Virus (RSV) in infants. Maternal immunization using the ABRYSVO vaccine between the 24th and 36th week of pregnancy has shown significant success. Data from a British vaccination program indicates that administering the vaccine at least four weeks before birth reduces the risk of RSV-related hospitalizations in infants up to six months old by 84.9 percent. For preterm infants, vaccine effectiveness was observed at 69.4 percent.

However, a large-scale observational study in France has identified resistance to the monoclonal antibody nirsevimab in certain RSV-B variants. Analyzing over 1,000 infant cases, researchers found that 12.5 percent of breakthrough infections in infants who had received nirsevimab involved resistant RSV-B strains, compared to only 1.0 percent in RSV-A cases. These mutations, which affect the viral F protein, appear to emerge under selective pressure following prophylaxis rather than circulating widely in the general community. Notably, some resistant variants were detected nearly a year after the administration of the antibody.