Nirsevimab for Prevention of RSV Disease

Posted by Carla Rothaus

Was nirsevimab effective in preventing RSV infection in the trial by Griffin et al.?

Because the only approved treatment for respiratory syncytial virus (RSV) infection (ribavirin) is difficult to deliver and has limited efficacy, the standard of care for patients with serious RSV illness is supportive management of the condition. There is a need for RSV prophylaxis in healthy infants. Griffin et al. evaluated a single dose of nirsevimab prophylaxis in healthy preterm infants entering their first RSV season. Read the NEJM Original Article here.

Clinical Pearls

Q: What subset of children are at particularly high risk for severe lower respiratory tract RSV infection?

A: RSV is the most common cause of lower respiratory tract disease and hospitalizations for respiratory illness among infants and young children, resulting in largely predictable annual epidemics worldwide. RSV is a leading cause of infant deaths, primarily in low-income and middle-income countries. During the first year of life, infants with a primary RSV infection are at risk for a severe lower respiratory tract infection. Preterm infants, as well as young children with chronic lung disease of prematurity or congenital heart disease, are at particularly high risk.

Q: What proportion of the annual U.S. birth cohort receives RSV prophylaxis?

A: Despite more than 50 years of attempts at vaccine development and extensive ongoing clinical research, there is no safe and effective RSV vaccine. Passive RSV antibody approaches have been effective in clinical studies. RSV prophylaxis is currently available as a specific RSV immune globulin G (palivizumab), administered in five monthly injections, that is licensed for infants who are at highest risk for serious RSV sequelae. Further restrictive recommendations have been issued by local and national bodies, limiting prophylaxis to less than 2% of the annual U.S. birth cohort. Currently, there is no approved RSV prophylaxis for healthy infants.

Morning Report Questions

Q: Was nirsevimab effective in preventing RSV infection in the trial by Griffin et al.?

A: This trial of a monoclonal antibody with an extended half-life showed that a single intramuscular dose of RSV immunoprophylaxis could protect infants against RSV-associated lower respiratory tract infection requiring medical attention. A single intramuscular injection of nirsevimab at a dose of 50 mg resulted in a lower incidence of medically attended RSV-associated lower respiratory tract infections and hospitalizations (approximately 70% and 80% lower, respectively) than placebo in healthy preterm infants entering their first RSV season. Of participants hospitalized because of RSV infection, all those who were admitted to the intensive care unit (5 participants) or received assisted ventilation (4 participants) were in the placebo group. Subgroup analyses of the primary and secondary efficacy end points showed results similar to those of the overall analysis, consistently favoring nirsevimab.

Q: Might nirsevimab have a role as RSV prophylaxis in healthy full-term infants?

A: Nirsevimab has greater neutralizing activity and a longer serum half-life than palivizumab. One injection of nirsevimab provided protection for a typical RSV season, whereas monthly injections of palivizumab are required to provide sustained protection during the RSV season. Palivizumab is indicated and recommended only for the highest-risk infants. Given the unique characteristics of nirsevimab, including this trial’s finding that season-long protection from RSV can be achieved with a single dose, it is currently being evaluated in healthy late-preterm and full-term infants.

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