New Shot Effective in Preventing RSV Hospitalization in Infants: Study

Marina Demidiuk/Shutterstock

Infants are likely to avoid hospitalization thanks to a dose of nirsevimab during their first RSV season, a new study reports. The newly approved drug can help young children stay protected from the highly contagious respiratory illness that hospitalizes between 58,000 and 80,000 children under the age of 5 in the United States each year.

Nirsevimab is a monoclonal antibody that neutralizes respiratory syncytial virus (RSV). During 2022 and 2023, when RSV was spreading rampantly throughout communities, the European Union, United Kingdom, Canada, and the U.S. all approved the use of nirsevimab in neonates and infants during their first RSV season.

The new study—funded by Sanofi and AstraZeneca—indicates that a first dose of nirsevimab can act as a vaccine of sorts against hospitalization due to RSV. Symptoms of RSV include runny nose, decreased appetite, coughing, sneezing, fever, and wheezing. Hospitalization often occurs when pneumonia, severe infection, and severe dehydration set in.

To determine nirsevimab’s efficacy at preventing hospitalization, the research team randomly assigned infants from France, Germany, and the United Kingdom who were a year or younger to either receive or not receive a single dose of nirsevimab before they entered their first RSV season. All of the infants were born before or during the RSV season, which began on Sept. 11, 2022, in France, Oct. 9, 2022, in Germany, and Sept. 4, 2022, in the United Kingdom. Of the infants enrolled in the study, 27 percent were from France, 22 percent were from Germany, and 50 percent were from the United Kingdom. Nearly 1 in 4 of the infants were classified as neonates, or infants who were less than 28 days old.

A total of 8,058 infants were included in the study, with 4,037 infants receiving nirsevimab and 4,021 infants receiving standard care, or no nirsevimab.

The research team discovered that nirsevimab helped prevent hospitalization. Just 11 infants in the nirsevimab group were hospitalized, versus 60 in the standard care group, representing a nirsevimab efficacy rate of 83.2 percent. Very severe RSV occurred in five infants in the nirsevimab group, versus 19 infants in the standard care group. Two of the five infants from the nirsevimab group were admitted to the intensive care unit and one was intubated and eventually received mechanically ventilated support. Five of the 19 infants from the standard care group were admitted to the ICU and 15 infants from the group were diagnosed with bronchiolitis.

RSV is by no means a new illness. The pathogen was discovered in 1956 and is the leading cause of acute respiratory illness worldwide. It is only in the last handful of years that the virus has become more chronic. There were an estimated 33 million cases of acute lower respiratory tract infection due to RSV in 2019; 3.6 million of those cases were hospitalized.

“Given the high burden of the illness associated with RSV, effective prevention measures are essential,” Doctor Natasha B. Halasa, Professor of Pediatrics at Vanderbilt University, wrote in an editorial in the New England Journal of Medicine.

A vaccine was created in the 1960s, but it was associated with fatal adverse reactions and, since then, no vaccine has been available for children. According to research, 80 percent of children who received the vaccine ended up sick and two died. Nirsevimab can be considered a game-changer as the first vaccine-of-sorts to be available since the formalin-inactivated RSV vaccine created in 1966.

“The introduction of nirsevimab brings a wave of excitement because if offers a more practical, single-dose alternative to previous interventions and extends protection to all infants,” Dr. Halasa wrote in her editorial.

In addition to nirsevimab, maternal vaccination is another relatively new option for protection for infants against RSV. The U.S. Centers for Disease Control and Prevention recommends pregnant women who are between 32 and 36 weeks pregnant during September through January get one dose of maternal RSV vaccine to protect their babies.