A candidate vaccine to prevent Zika virus (ZIKV) infection was safe and induced persistent neutralizing antibody responses in a phase 1 study. Janssen's Ad26.ZIKV.001 is a viral-vectored vaccine with a replication-incompetent adenoviral vector encoding the ZIKV M and Env proteins. The study tested a lower and a higher dose of vaccine administered intramuscularly in a one- or two-dose regimen schedule, with the second dose given 56 days after the first dose, in 100 healthy adult volunteers (55% women). All vaccine regimens were "well tolerated, with no safety concerned identified," the study team led by Dr. Nadine Salisch, with Janssen Vaccines and Prevention, Leiden, the Netherlands, reports in Annals of Internal Medicine. Further, they say potent neutralizing antibody responses developed after a single lower or single higher dose of the vaccine and a second dose increased antibody titers. Antibody responses persisted for at least one year for all regimens, with somewhat lower titers in those receiving the single lower-dose of vaccine. Transferred antibodies were found to protect mice against Zika virus infection. This study "supports further clinical development if an unmet medical need emerges," the authors say. The co-authors of a linked editorial agree and say "candidate ZIKV vaccines proven safe in phase 1 trials should immediately be assessed for safety and efficacy in pregnant women (as) this group is a major target for ZIKV immunization both to protect the fetus and for the transfer of antibodies that might protect against early postnatal infection." "Although ZIKV currently is not circulating at epidemic levels, endemic infections persist in several countries (10) and a resurgence of infection is certainly possible, especially as immunity wanes in areas of previous outbreaks. In addition, ZIKV outbreaks in 2015 to 2016 were highly regional, meaning that large sections of the affected countries (including the United States) do not have protective levels of immunity," write Dr. Ann Chahroudi of Emory University in Atlanta and Dr. Sallie Permar with NewYork Presbyterian/Weill Cornell Medical School in New York. "The coronavirus disease 2019 pandemic," they add, "has taught us that preparedness for emerging infections is crucial. Unfortunately, enthusiasm and funding for infectious diseases that are not in the public eye fade, leading countries to be caught off guard, as evidenced by SARS-CoV-1, Middle East respiratory syndrome, Ebola, ZIKV, and SARS-CoV-2 outbreaks." "A prophylactic vaccine for ZIKV infection and blood supply screening that is responsive to real-time viral surveillance are tangible public health measures that will prevent future disease in vulnerable populations and that we should prioritize," Drs. Chahroudi and Permar conclude. Funding for the study was provided by Janssen Pharmaceuticals and the U.S. Army have a Cooperative Research and Development Agreement. Author disclosures are available with the original article. —Reuters Staff Source
