Could There Be a Zika Vaccine Soon?

According to the CDC, 4175 cases of Zika virus infections have been reported in the United States. So far, no vaccine exists to prevent the virus, but vaccine candidates are in the works.

At the Walter Reed Army Institute of Research (WRAIR) Clinical Trial Center in Silver Spring, Maryland, the first stage of a human-based clinical trial to test an investigational Zika vaccine candidate has begun.

The candidate, called the Zika Purified Inactivated Virus (ZPIV) vaccine, is being evaluated for its safety and ability to generate an immune-system response. The ZPIV vaccine is based on the same technology used to successfully develop a vaccine for another flavivirus called Japanese encephalitis in 2009.

Another Zika vaccine candidate, a DNA-based vaccine, showed promising results, as well, in early trials and is on track for phase 2 of field testing in January 2017. Locations where Zika transmission is prevalent will be targeted.

However, the ZPIV vaccine takes on a different strategy than the DNA vaccine. The vaccine triggers an immune response by carrying inactivated whole Zika virus particles. The protein shell of the inactivated virus remains intact so that it can be recognized by the immune system. Preclinical development of the experimental vaccine, which included safety and nonhuman primate studies, successfully proved effective against Zika in the primates.

The new study evaluates 75 people aged 18 to 49 years with no prior flavivirus infection, such as Zika virus, yellow fever virus, dengue virus, Japanese encephalitis virus, and West Nile virus. Participants were randomly divided into 3 groups: group 1 will receive 2 intramuscular injections of the vaccine or a placebo (saline) 28 days apart, and the other 2 groups will either receive a 2-dose regimen of a Japanese encephalitis virus vaccine or 1 dose of a yellow fever vaccine before beginning the 2-dose ZPIV vaccine. Additionally, a subgroup of 30 participants will receive a third dose of the ZPIV vaccine 1 year later.

The WRAIR study is likely to be completed by fall 2018, and 4 additional clinical studies are expected to take place in the next few months.