RSV Immunization Shows Promising Results in Phase 3 Trials

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Nirsevimab, a potential respiratory syncytial virus (RSV) immunization, protects healthy infants against infections in phase 3 trials.

The ease in global COVID-19 restriction has led to a surge in influenza cases across the world. As a result, doctors are urging people not to skip their yearly flu boosters. However, adults are not the only ones at risk of rising viral infections. Hospitals across the United States have been reporting a rise in respiratory syncytial virus (RSV) cases among children. Since there are no specific treatments for the infection, scientists are on the search for specific antivirals and vaccines. But a recently published study has now demonstrated the success of the first potential RSV immunization.

Respiratory syncytial virus (RSV) is a leading cause of pneumonia and bronchiolitis in infants. It causes seasonal respiratory tract infections in children, often requiring hospitalization. Although there is no specific treatment for the infection, palivizumab is the only drug that provides protection against RSV infections. However, it is only given to high-risk children and five monthly injections for required for complete protection.

The phase 3 trial included approximately 1500 healthy term and late preterm infants. At the start of the RSV season, researchers administered a single intramuscular injection of nirsevimab or placebo to the children. Nirsevimab is a long-acting monoclonal antibody designed to prevent RSV-related lower respiratory tract infections.

The results of the trial are available in the New England Journal of Medicine.

Safe and Effective

According to the results, nirsevimab demonstrated a 74.5% efficacy against medically attended RSV infections. Thus, revealing that just a single dose of the drug is enough to provide safe protection against the entire RSV season.

In a separate phase 2/3 trial, researchers also assessed the safety and tolerability of the drug in preterm infants with chronic lung disease or congenital heart disease. Results revealed a similar safety profile as palivizumab. Moreover, the drug demonstrated a similar efficacy for the study participants as the healthy infants in the previous trial.

We know that RSV has seen a resurgence with the easing of COVID-19 public health measures. This shows us a broad immunization approach is needed to help mitigate the substantial global burden RSV places on infants, their families and healthcare services.

Dr. William Muller, principal investigator and co-author


New England Journal of Medicine (2022). DOI: 10.1056/NEJMoa2110275


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