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Antibody Shot Could Cut Infant RSV Hospitalizations by 80%

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The preventative antibody shot niresvimab protects against hospitalization of infants infected with respiratory syncytial virus (RSV), according to results from a new clinical trial. The research is published in The New England Journal of Medicine.

What is RSV?

RSV causes seasonal infections in infants, resulting in symptoms such as a runny nose, coughing, fever, low appetite and wheezing. Approximately two in three children in their first year of life experience RSV infection, and nearly all infants have an infection by the age of two.

Though most experience a mild infection, RSV can cause a severe illness known as lower respiratory tract disease (LRTD), with infants experiencing a first infection being particularly at risk.

RSV causes approximately 58,000–80,000 hospitalizations among children under 5 each year in the US, and it is the leading cause of hospitalization in infants.

“The winter surge of bronchiolitis admissions, caused by RSV infecting infants, regularly puts severe pressure on children’s health services,” said Prof. Callum Semple, professor of child health and outbreak medicine at the University of Liverpool.

Niresvimab, also known as Beyfortus, was approved by the US Food and Drug Administration in July 2023 to prevent LRTD in babies and toddlers. Now, the new study’s findings suggest that the drug could reduce hospital admissions by around 80%.

Preventing RSV hospital admissions

“In effect, this is a vaccine, working not by stimulating the immune system to make antibody but by providing that antibody directly,” explained Prof. Peter Openshaw, a professor of experimental medicine at Imperial College London.

The trial assessed niresvimab’s efficacy in preventing hospitalizations with RSV-associated lower respiratory tract infections.

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Infants across the UK, France and Germany received either a single injection with niresvimab (4,037 infants) or standard care (i.e., no intervention; 4,021 infants) before or during their first RSV season.

The researchers found niresvimab was 83.2% effective in preventing hospitalizations – 0.3% of the niresvimab-treated infants were hospitalized, compared to 1.5% of the infants who received standard care.

Niresvimab was also 75.7% effective in preventing very severe RSV-associated lower respiratory tract infections, defined as infections resulting in less than 90% blood oxygen saturation and requiring supplemental oxygen. This occurred in 0.1% and 0.5% of infants in the nirsevimab and standard-care groups, respectively.

These results are a “splendid result for babies, their families and our health services,” Semple said.

“This and other long-acting antibody preparations are a major step forward in preventing a major cause of infantile illness,” explained Openshaw.


Reference: Drysdale SB, Cathie K, Flamein F, et al. Nirsevimab for prevention of hospitalizations due to RSV in infants. NEJM. 2023;389(26):2425-2435. doi: 10.1056/NEJMoa2309189