Results announced in vaccine for respiratory syncytial virus disease

Novavax, Inc.announced results from Prepare, a global Phase III clinical trial using ResVax an aluminum adjuvanted respiratory syncytial virus (RSV) fusion (F) protein recombinant nanoparticle vaccine. ResVax is being developed to protect infants via maternal immunization against RSV disease.

In the Prepare trial, efficacy of ResVax against the primary and two secondary endpoints in per-protocol infants with RSV lower respiratory tract infection (LRTI) through 90 days of life was: 39% against medically significant RSV LRTI (97.5%CI, -1% to 64%). 44% against RSV LRTI hospitalizations (95%CI, 20% to 62%). 48% against RSV LRTI with severe hypoxemia (95%CI, -8% to 75%). Pre-specified exploratory analyses of these same vaccine efficacy endpoints, which include additional data ascertained from hospitalization records, were: 41% against medically significant RSV LRTI (95%CI, 16% to 58%). 42% against RSV LRTI hospitalizations (95%CI, 17% to 59%). 60% against RSV LRTI with severe hypoxemia (95%CI, 32% to 76%) .

Other observations from the Prepare trial : Reduction in all-cause LRTI hospitalizations (25%) and all-cause LRTI severe hypoxemia (39%) in infants observed through the first 180 days of life. Mothers vaccinated from 28 up to < 33 weeks of pregnancy, showed vaccine efficacy rates against RSV LRTI hospitalization of 53% and severe RSV hypoxemia of 70% through the first 90 days of their infants’ lives, compared with 26% and 44% for mothers vaccinated ? 33 weeks of pregnancy. Over 90% of RSV LRTI hospitalizations and RSV LRTI severe hypoxemia in the placebo group occurred in the first 90 days of life. 99% of vaccinated mothers had measurable antibody responses to the vaccine, with ?100% transplacental transfer for all antibody types measured. ResVax appears safe in mothers and their infants through 180 days post-delivery .

" While this study did not meet the pre-specified success criterion for the primary clinical endpoint of this trial, the data indicate that ResVax protects infants from some of the most serious consequences of RSV, including RSV LRTI hospitalizations and RSV LRTI with severe hypoxemia,” said Stanley C. Erck, President and Chief Executive Officer of Novavax, Inc. “The potential to prevent these most serious outcomes during infants’ most vulnerable months of life could have a profound impact upon the global burden of RSV disease. Our next steps include meeting with U.S. and European regulators to review these data and to discuss the path forward for licensure".

Comment: Infants born to women in the vaccine group posted an incidence rate of about 1.5% compared to the control group's rate of 2.4%. That improvement, of about 40%, was not enough to meet statistical level for declaring success. The improvement rates for some of the secondary endpoints, such as on RSV hospitalizations and cases with severe hypoxemia, were modestly better at 44% and 48% respectively.