Critical research focused on preventing and controlling the impact of the Zika virus is ongoing, with several new tests and vaccines on the horizon. The disease caused by the Zika virus is known to spread to humans through the bite of an Aedes species mosquito carrying the infection, and can also be passed from an infected person to their fetus or sex partner. Often the Zika virus causes no or only mild symptoms that last up to a week; however, when Zika infection occurs during pregnancy, fetal outcomes have resulted, including microcephaly, neurological complications, and Guillain-Barré syndrome. According to the World Health Organization, the advancement of research and development of vaccines, diagnostics, and innovative vector control tools is a top priority.
As a strong effort to prevent Zika virus infection, the National Institute of Allergy and Infectious Diseases (NIAID) is working to develop multiple vaccine candidates. An early-stage trial began in August 2016 for a DNA-based vaccine that uses a strategy similar to an existing investigational flavivirus vaccine for West Nile virus. Another investigational Zika vaccine builds on a similar live-attenuated vaccine approach for dengue virus, which is closely related to Zika. There is also an early-stage investigational vaccine using a genetically engineered version of vesicular stomatitis virus, which is an animal virus that primarily targets cattle; plans are underway to continue the study in tissue culture and animal models. Additionally, an approach similar to that used by the Walter Reed Army Institute of Research to develop Japanese encephalitis and dengue virus vaccines is in progress to create a whole-particle inactivated Zika vaccine.
NIAID has recently initiated testing of an investigational vaccine in humans. The investigational vaccine to be tested includes a small, circular piece of DNA engineered to contain genes that code for proteins of the Zika virus. When injected, cells respond by reading the genes and making Zika virus proteins, creating an immune response. The clinical trial will involve three US study sites where 80 healthy volunteers ages 18-35 years will be divided into groups of 20. All volunteers will receive a vaccination at their first visit, and half of the volunteers will return for one additional vaccination eight or 12 weeks later. The remaining participants will receive two additional vaccinations. All participants will return for follow-up visits within a 44-week time period after the first vaccination to determine safety; investigators will also take blood samples for lab testing to measure the immune response. Participants will be asked to return for two follow-up visits at 18 months and two years following the initial vaccination. Initial safety and immunogenicity data from the Phase 1 trial are expected by January 2017. If a favorable safety profile and immune response are demonstrated, the NIAID plans to initiate a Phase 2 trial in early 2017. The development process for an effective vaccine is well underway, so though there is much research yet to be done, the progress to date has been significant.
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Salvatore Volpe, MD, FAAP, FACP, CHCQM
Chief Medical Officer