More real-world evidence shows nirsevimab protects infants against RSV
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Key takeaways:
- The United States was one of four countries that implemented nirsevimab last winter.
- The monoclonal antibody prevented hospitalization for RSV-associated bronchiolitis.
The monoclonal antibody nirsevimab reduced the risk that infants would be hospitalized for respiratory syncytial virus-associated bronchiolitis, according to a study published Wednesday in The New England Journal of Medicine.
Last August, the CDC recommended nirsevimab as an option to protect infants against RSV, which is the leading cause of hospitalization among babies in the United States. The AAP recommended nirsevimab for all infants aged younger than 8 months.
Nirsevimab is one of two monoclonal antibody shots that can be given to infants to protect them against RSV. There is also a maternal RSV vaccine.
The new study, which assessed nirsevimab’ effectiveness among infants in France, was not the first to demonstrate its real-world benefits. In March, researchers reported in MMWR that nirsevimab was 90% effective at preventing RSV hospitalization among infants in the U.S.
“Following the strong reduction of RSV circulation during the COVID-19 pandemic, we faced an unprecedented RSV bronchiolitis outbreak during the 2022/2023 winter that completely overwhelmed health care resources worldwide,” Naim Ouldali, MD, PhD, a researcher in the departments of general pediatrics, pediatric infectious disease and internal medicine at Robert Debré University Hospital in Paris, told Healio. “Several names, including ‘immune debt’ and ‘immunity gap,’ have been proposed to describe this phenomenon that urges us to develop and implement new preventive strategies to address this emerging issue.”
According to Ouldali, only four countries implemented nirsevimab last winter — France, Luxembourg, Spain and the U.S. Ouldali and colleagues conducted their case-control study among all infants aged younger than 12 months who were hospitalized for RSV-associated bronchiolitis between Oct. 15 and Dec 10 last year at six hospitals in France.
In all, the researchers examined 690 cases of RSV-related bronchiolitis that occurred during the winter surge in infants (median age, 3.1 months) matched with a control cohort of 345 infants (median age, 3.4 months) hospitalized for reasons other than RSV.
“To reduce the risk for bias, cases and controls were matched for age, date of hospital visit, and center,” Ouldali said. “Multivariate regression adjusted for confounders was performed to calculate nirsevimab effectiveness.”
Overall, 8.7% of case patients had received nirsevimab compared with 28.1% of matched controls.
Results showed an estimated adjusted effectiveness of nirsevimab therapy against hospitalization for RSV-associated bronchiolitis of 83% (95% CI, 73.4%-89.2%), according to Ouldali and colleagues.
In addition, researchers found that the efficacy of nirsevimab against RSV-associated bronchiolitis that resulted in critical care was 69.6% (95% CI, 42.9%-83.8%), and 67.2% (95% CI, 38.6%-82.5%) against RSV-associated bronchiolitis resulting in ventilatory support.
Ouldali noted that the study took place at a time when the level of natural protection — including from pregnant mothers who pass RSV antibodies to newborns — was expected to be high, given the previous season’s intense circulation of RSV.
“This shows that whatever the context of previous RSV circulation, nirsevimab seems to provide a very satisfying protection against severe RSV bronchiolitis in infants,” Ouldali said.
Reference:
Perspective
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This article adds to a growing body of literature describing the real-world effectiveness of nirsevimab. Results from the phase 3b HARMONIE trial of nirsevimab prior to licensure found efficacy of 89.6% (adjusted 95% CI, 58.8%-98.7%) against hospitalization for RSV-associated lower respiratory tract infection. While the HARMONIE trial approximated real-world settings, it is critical to evaluate the clinical effectiveness of therapies after licensure.
Reassuringly, [the current] study found real-world effectiveness of nirsevimab therapy against hospitalization for RSV-associated bronchiolitis of 83% (95% CI, 73.4%-89.2%). Early estimates of effectiveness from the New Vaccine Surveillance Network published in March found similar effectiveness of 90% (95% CI, 75%-96%).
It is highly reassuring to see a body of literature build with similar outcomes despite varied study designs, including different locations, patient populations and across RSV seasons. We can rely on the mounting evidence that passive immunization with nirsevimab is an effective preventative measure to reduce this burden of hospitalizations due to RSV. With this data, providers can feel confident in providing a strong recommendation for nirsevimab for babies entering their first RSV season.
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