The Walter Reed Army Institute of Research (WRAIR) Clinical Trial Center, part of the US Department of Defense (DoD) has initiated the first of the five early stage clinical trials of the Zika Purified Inactivated Virus (ZPIV) vaccine to generate an immune system response.

Co-funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), the trial is planning to include 75 people aged 18 to 49 with no prior flavivirus infection.

The subjects will be randomised into three groups, where the first group of 25 participants will receive two intramuscular injections of the ZPIV test vaccine or a placebo (saline) 28 days apart, and the other two groups with 25 participants each will receive a two-dose regimen of a Japanese encephalitis virus vaccine or one dose of a yellow fever vaccine before the two-dose ZPIV vaccine regimen.

A subgroup of 30 participants who receive the two-dose ZPIV regimen will also receive a third dose after one year.

"We are pleased to be part of the collaborative effort to advance this promising candidate vaccine into clinical trials."

The ZPIV vaccine is based on another WRAIR developed flavivirus vaccine for Japanese encephalitis.

The experimental vaccine contains whole Zika virus particles that have been inactivated, which means that the virus cannot replicate and cause disease in humans but the protein shell remains intact for its detection by immune system and evoke an immune response.

The development of the ZPIV vaccine was partially supported by the NIAID, which included safety testing and non-human primate studies that found the vaccine induced antibodies that neutralised the virus.

A joint Research Collaboration Agreement was formed by WRAIR, NIAID and the Biomedical Advanced Research and Development Authority (BARDA) part of the HHS Office of the Assistant Secretary for Preparedness and Response (ASPR) to support the development of this vaccine.

NIAID director Anthony Fauci said: “We urgently need a safe and effective vaccine to protect people from the Zika virus infection as the virus continues to spread and cause serious public health consequences, particularly for pregnant women and their babies.

“We are pleased to be part of the collaborative effort to advance this promising candidate vaccine into clinical trials.”