Nirsevimab effective against RSV in late preterm, term infants
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Researchers at IDWeek reported more promising news about nirsevimab, an investigational single-dose monoclonal antibody that has previously been shown to protect preterm infants against respiratory syncytial virus.
It was found to be effective against medically attended RSV lower respiratory infection in a phase 3 trial of late preterm and term infants, according to the results of the phase 3 MELODY trial.
Presenting author Laura Hammitt, MD, associate professor in the department of international health at Johns Hopkins Bloomberg School of Public Health, collaborated on the research with physicians from Israel, Spain, Bulgaria, South Africa, Sweden and the U.S.
“RSV is the most common cause of childhood acute lower respiratory tract infection, and nearly all children will have an RSV infection by the age of 2,” Hammitt said in her presentation. “In addition to a very substantial outpatient burden of disease, RSV is also a major reason for hospitalization in young children around the world, and that occurs regardless of national economic status.”
The U.S. has experienced an offseason surge of RSV, which began to increase in the spring around the same time that states began relaxing COVID-19 mitigation measures. Just before the pandemic, one study reported that more than 49,000 pediatric hospitalizations from RSV occurred during the 2014-2015 season.
Hammitt added that while palivizumab (Synagis, MedImmune) is approved for RSV prevention in infants born prematurely or with an underlying lung or heart disease, doctors have sought a way to prevent RSV in term infants who are otherwise healthy.
Nirsevimab (AstraZeneca, Sanofi) has an extended half-life, which allows for a once-per-season dosing.
In the phase 3 study, Hammitt and colleagues randomly assigned 1,490 late preterm and term infants at 150 sites around the world to receive either one intramuscular injection of nirsevimab (n = 994) — at 50 mg if they weighed less than 5 kg or 100 mg if they weighed more than 5 kg at dosing — or placebo (n = 496). They began enrolling participants in July 2019 and suspended enrollment in March 2020 because of the pandemic.
According to the researchers, medically attended RSV was reported in 1.2% of infants who received nirsevimab and 5% of infants who received placebo. Nirsevimab was 70.1% efficacious against medically attended RSV and 78.4% efficacious against RSV hospitalization, the researchers reported.
“In these infants, 93.6 cases of medically attended RSV of any cause were averted per 1,000 infants immunized, which translates to 11 infants needing to be immunized for about one case of medically attended RSV of any cause,” Hammitt said. “Based on these results nirsevimab really has the potential to be an important intervention to reduce the burden of RSV in healthy infants.”
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Hammitt L, et al. Abstract LB13. Presented at: IDWeek; Sept. 29-Oct. 3, 2021 (virtual meeting).
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