NIH Begins Phase 2 Zika Vaccine Trials

Zika Vaccine at Laboratory
Zika Vaccine at Laboratory
The National Institute of Allergy and Infectious Diseases began phase 2/2b of a multisite clinical trial of an investigational vaccine against the Zika virus.

An investigational DNA vaccine against the Zika virus, developed by scientists at the Vaccine Research Center (VRC) of the US National Institute of Allergy and Infectious Diseases (NIAID) has entered phase 2/2b of clinical trial testing. 

The multisite phase 2/2b trial called VRC 705, led by Julie E. Ledgerwood, DO, chief of the VRC’s clinical trials program, and Grace L. Chen, MD, deputy chief of VRC, aims to enroll at least 2490 participants in areas of confirmed or potentially active mosquito transmitted Zika infection including the continental United States, Puerto Rico, Brazil, Peru, Costa Rica, Panama, and Mexico.

The Zika virus DNA vaccine was developed based on a strategy used by the NIAID to develop the West Nile virus candidate vaccine. The Zika virus vaccine contains a DNA plasmid into which scientists have inserted genes encoding 2 proteins found on the surface of the Zika virus.

The VRC scientists state that the vaccine does not contain live infectious material so it cannot cause active Zika virus infection in participants.

After entering early-stage human testing in 2016, the VRC scientists intend to further determine the vaccine’s safety and ability to stimulate an immune response in Part A of phase 2/2b. Part A will enroll 90 healthy men and non-pregnant women age 18 to 35 in Houston, Texas; Miami, Florida; and San Juan, Puerto Rico.

Participants will be followed for 32 weeks, receiving a standard dose (4 mg) or a high dose (8 mg) of the vaccine intramuscularly at 3 clinic visits, 4 weeks apart. From there, participants will be tested for the ability to stimulate immune response to the vaccine, as well as the optimal dose and intramuscular injection site (arm vs thigh muscle).

In Part B of phase 2/2b, the scientist are looking to determine whether the vaccine can protect against Zika-related disease when someone is naturally exposed to the virus. Part B of the phase 2/2b will enroll 2400 healthy men and non-pregnant women age 15 to 35 in the 3 sites from part A as well as 2 additional sites in San Juan, Puerto Rico; 2 sites in Costa Rica; and one site each in Peru, Brazil, Panama, and Mexico.

Part B of phase 2/2b will be double-blinded, assigning study participants to receive either the investigational vaccine or placebo at 3 clinic visits, 4 weeks apart. Part B participants will be followed for 2 years, undergoing assessments of symptoms and adverse events from the virus.

“We are pleased to have advanced rapidly one of NIAID’s experimental Zika vaccines into this next stage of testing in volunteers. We expect this study will yield valuable insight into the vaccine’s safety and ability to prevent disease caused by Zika infection,” said Anthony S. Fauci, MD, director of NIAID.

The study is expected to be completed by 2019 but initial results could be available at the end of 2017.

For more information about the trial, visit Questions and Answers: VRC 705: Phase 2/2b Trial Testing the NIAID Zika Virus Investigational DNA Vaccine.

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Phase 2 Zika vaccine trial begins in US, Central and South America [news release]. Bethesda, Maryland: National Institutes of Health; March 31, 2017. Accessed April 5, 2017.