Zika Vaccine Proves Effective in Monkeys

WRAIR Zika Vaccine

In early July, the Walter Reed Army Institute of Research (WRAIR) confirmed that a Zika vaccine successfully prevented infection in mice. Yesterday, WRAIR announced that the same vaccine also proved successful in nonhuman primates.

In a study in Science, researchers published their findings on the efficacy of the Zika purified inactived virus (ZPIV) vaccine in preventing infection in rhesus monkeys in preclinical trials. The study analyzed vaccine efficacy against two strains of the virus: ZIKV-BR; Brazil/ZKV2015 and ZIKV-PR; PRVABC59 (from Puerto Rico). In the study, monkeys were experimentally infected with the two strains, after which they received two vaccine doses, within four weeks of each other.

Viremia in control group monkeys persisted for 6-7 days after infecton, detectable in urine, cerebrospinal fluid, colorectal secretions, and cervicovacinal secretions. Monkeys in the control group did not have differing viral loads based on the type of strain they were infected with. On the other hand, in monkeys who received the vaccine, no virus was detected in blood, urine, colorectal secretions, cerebrospinal fluid, or cervicovaginal secretions. Due to low sample volume, study researchers could not test viremia in semen.

According to the authors, “All PIV vaccinated animals developed ZIKV Env-specific binding antibodies by ELISA as well as ZIKV-specific neutralizing antibodies by microneutralization (MN50) assays at week 2 following initial immunization.”

Zika Situation Update

Currently, there is active Zika transmission in Miami-Dade County, in Florida, with one newly-identified locally-acquired case, bringing the total of locally-acquired cases to 16, and travel-related cases to 351. According to the Florida Department of Health, of the infected individuals, 55 were pregnant women, for whom Zika virus poses the greatest threat, since infection has been confirmed to cause congenital neurological complications in developing fetuses. A recent Zika update notes that the new case was the only one to test positive for Zika virus out of the 142 newly-tested individuals in the infected area.

Due to the complications associated with Zika virus infection, vaccine development remains imperative. The WRAIR preclinical trial findings bring researchers one step closer to creating a Zika vaccine for humans. WRAIR will be working alongside the National Institute of Allergy and Infectious Diseases (NIAID) Division of Microbiology and Infectious Disease and Vaccine Research Center to test ZPIV in a Phase I human trial, which is expected to start later this year.