A brand new examine in The Lancet Infectious Illnesses describes the genotypic and phenotypic traits of respiratory syncytial virus (RSV) breakthrough infections after the widespread use of the monoclonal antibody nirsevimab (Beyfortus) in infants youthful than 1 12 months.
The examine was primarily based on outcomes seen amongst infants in France through the 2023-2024 RSV season, the primary season the RSV antibody was permitted to be used in infants within the European Union and the US. In France, roughly 210,000 single doses have been administered final 12 months.
To grasp the real-life potential for viral escape, the authors checked out 260 RSV full-length viral genome sequences from nirsevimab-treated infants with breakthrough infections and in contrast the RSV RNA to that from 285 untreated RSV-infected infants.
Within the breakthrough infections, 236 instances (91%) have been RSV-A, and 24 (9%) have been RSV-B.
Resistance solely seen in RSV-B instances
There have been no recognized nirsevimab resistance–related mutations in infections attributable to RSV-A, and solely 2 of the 24 RSV-B infections confirmed a mutation that conferred resistance to nirsevimab.
Total, breakthrough infections in France have been uncommon, the authors mentioned, and the antibody ought to be used once more within the upcoming RSV seasons.
As nirsevimab use turns into extra widespread, collaboration between analysis and public well being companies turns into important to evaluate the emergence of resistance.
In a commentary on the examine, the authors write, “This discovering underscores the necessity for subgroup-specific surveillance methods to assist higher clarify the completely different prevalences of monoclonal antibody-escape mutants between RSV-A and RSV-B. As nirsevimab use turns into extra widespread, collaboration between analysis and public well being companies turns into important to evaluate the emergence of resistance.”
