Studies ‘offer hope’ for RSV prevention
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Results from two trials published recently in The New England Journal of Medicine “offer hope” in the ongoing search for a way to prevent respiratory syncytial virus, an expert said.
In the first trial, one injection of an investigational monoclonal antibody, nirsevimab, lowered the incidence of medically attended RSV-associated lower respiratory tract infections and hospitalizations compared with placebo among healthy preterm infants, researchers reported.
In the second trial, an investigational RSV vaccine administered to pregnant women was nearly 40% effective against RSV-associated, medically significant lower respiratory tract infection among newborns. The results “did not meet the prespecified criterion for success,” the researchers wrote, although there was evidence of potential secondary benefits from the vaccine.
“Both approaches offer hope that an effective means for preventing RSV infections may finally be in sight,” Infectious Diseases in Children Editorial Board Member H. Cody Meissner, MD, chief of the division of pediatric infectious diseases at Floating Hospital for Children at Tufts Medical Center and professor of pediatrics at Tufts University School of Medicine, wrote in an accompanying editorial.
The first trial was conducted at 164 sites in 23 countries in the southern and northern hemisphere. M. Pamela Griffin, MD, of MedImmune LLC, and colleagues randomly assigned healthy preterm infants — born between 29 weeks to 34 weeks, 6 days of gestation — in a 2:1 ratio to receive a single 50 mg injection of nirsevimab or placebo at the beginning of RSV season. The trial included 1,453 participants, and 969 received nirsevimab. The researchers observed infants for 150 days after administration.
According to the results, the incidence of medically attended RSV-associated lower respiratory tract infection was 70.1% lower (95% CI, 52.3-81.2) in the nirsevimab group compared with the placebo arm (2.6% vs. 9.5%).
In the incidence of hospitalization for lower respiratory tract infection was 78.4% lower (95% CI, 51.9-90.3) in those who received nirsevimab than those who received placebo (0.8% vs. 4.1%).
The authors reported that the differences were consistent throughout the 150-day follow-up period.
In the second trial, Shabir A. Madhi, MBBCH, FCPaeds, PhD, professor of vaccinology at the University of the Witwatersrand in Johannesburg, and colleagues randomly assigned 4,636 healthy pregnant women expected to give birth around RSV season a single intramuscular dose of RSV fusion protein nanoparticle vaccine.
Among 4,579 live births, the percentage of infants with RSV-associated medically significant lower respiratory infection was 1.5% in the vaccine group and 2.4% in the placebo group in the first 90 days, for an estimated vaccine efficacy of 39.4% (97.52% CI, –1 to 63.7; 95% CI, 5.3-61.2).
The percentages of RSV-associated medically significant lower respiratory tract infection with severe hypoxemia were 0.5% for the vaccine group and 1% for those taking the placebo (efficacy = 48.3%; 95% CI, –8.2 to 75.3). The percentages of those requiring hospitalization were 2.1% for those taking the vaccine and 3.7% for the placebo group (efficacy = 44.4%; 95% CI, 19.6-61.5).
The rate of reactions at the local injection site was 40.7% for women with the vaccine compared with 9.9% of the women who received the placebo.
“The development of a safe and effective RSV vaccine has been a goal for decades,” Meissner wrote. “However, negative experience with a formalin-inactivated RSV vaccine that was evaluated in young children in the 1960s” — which worsened symptoms in some infants, killing two — “led to ongoing concerns about potential untoward effects of a nonlive RSV vaccine.”
Meissner said similar concerns “resonate today” amid vaccine development for SARS-CoV-2, the RNA respiratory virus that causes COVID-19.
“For more than 50 years, RSV vaccine development has been a goal,” Meissner told Healio. “Because of recent developments in the science of vaccinology and greater understanding of the biology or RSV replication, considerable progress in vaccine development is being made.”
In his editorial, Meissner said the results of the trials provide a basis for further study of nanoparticle or alternative RSV vaccines.
“[It’s an] exciting time for RSV prevention and treatment modalities,” Meissner said. “A number of pharmaceutical companies are interested in developing novel approaches for either active or passive immunity.”
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