The New England Journal of Medicine has published results of a case-control study showing an estimated effectiveness of nirsevimab (Beyfortus) against hospitalization for respiratory syncytial virus (RSV)-associated bronchiolitis in babies of 83%.

Nirsevimab was approved by the US Food and Drug Administration in July 2023, and little real-world data on efficacy are available. The study aimed to establish efficacy rates during the most recent RSV season at six hospitals in France. 

The study was based on outcomes among 1,035 infants, of whom 690 were case-patients. Case-patients were infants younger than 12 months of age who were hospitalized for RSV-associated bronchiolitis from October 15 to December 10, 2023. Controls were infants with clinical visits to the same hospitals for conditions unrelated to RSV infection.

Good protection against severe outcomes

Infants who had previously received palivizumab—another monoclonal antibody used for RSV—and those whose mother had been vaccinated against RSV during pregnancy were excluded from the study. 

Overall, a nirsevimab injection had been received previously by 60 of 690 case-patients (8.7%) and by 97 of 345 (28.1%) matched control patients. The adjusted effectiveness of nirsevimab therapy against hospitalization for RSV-associated bronchiolitis was 83.0% (95% confidence interval [CI], 73.4% to 89.2%). 

The effectiveness of nirsevimab therapy against RSV-associated bronchiolitis leading to pediatric intensive care unit admission was 69.6% (95% CI, 42.9% to 83.8%) and leading to ventilatory support was 67.2% (95% CI, 38.6% to 82.5%).

In a real-world setting, nirsevimab therapy was effective in reducing the risk of hospitalized RSV-associated bronchiolitis.

"In a real-world setting, nirsevimab therapy was effective in reducing the risk of hospitalized RSV-associated bronchiolitis," the authors concluded. "This level of effectiveness was consistent across age groups."

Note: This story was updated on July 15, 2024, to clarify that this is a case-control study, not a randomized controlled trial.

A physician-led effort to remove penicillin allergy labels from low-risk patients at a Veterans Administration medical center removed the label in more than a third of those who were evaluated, researchers from Texas reported today in Open Forum Infectious Diseases.

Earlier studies have found that more than 95% of people reporting penicillin allergies, often labeled during childhood, are not truly allergic to penicillin and other beta-lactam antibiotics. The mislabeling or outdated labeling is a clinical problem, because patients with infections who don't have true penicillin allergies often receive antibiotics that aren't as effective, are more expensive, or are broad-spectrum antibiotics that increase the risk of Clostridium difficile and other adverse reactions.

Between November 2022 and December 2023, researchers screened 272 inpatient veterans who had penicillin allergy labels and interviewed 154 for possible delabeling. They delabeled 53 patients, 26 directly, 23 after an oral amoxicillin challenge, and 4 after outpatient allergy referral. Though the facility is large, it doesn't have onsite allergy physician coverage.

Successful results in patients with underlying comorbidities

Of the 53 patients who were delabeled, 25 later received penicillin-class prescriptions. No adverse events occurred in those who had undergone oral amoxicillin challenge. Researchers found that patients with low-risk penicillin allergy history were more likely to undergo a challenge if admitted with an infectious disease.

Only one inappropriate relabeling event occurred, which the team corrected. 

The researchers concluded that the findings demonstrate a successful provider-led system for removing penicillin allergy labels in US veterans who have complex comorbidities. "These findings add to the body of literature supporting the inpatient use of oral amoxicillin challenges by non-allergy providers as a means of expanding access to penicillin allergy evaluation," they wrote.