Efforts on the public health and research fronts continue to focus on the Zika virus, declared by the World Health Organization in 2016 as a public health emergency of international concern. The virus now has spread to 80 countries, including 50 in the Americas and Caribbean.¹

Zika infection during pregnancy can cause serious damage to the brain and microcephaly in developing fetuses, and can lead to congenital Zika syndrome in babies. This syndrome includes a pattern of birth defects, such as brain abnormalities, vision problems, hearing loss, and problems moving limbs. These babies may appear healthy at birth, but have underlying brain defects or other Zika-related health problems. In 2016, of the 250 U.S. pregnant women with a confirmed Zika infection in 2016, about one in 10 (24) had a fetus or baby with Zika-related birth defects.²

Interim Guidance

In October 2017, the Centers for Disease Control and Prevention (CDC) issued updated interim clinical guidance for healthcare providers caring for infants born to mothers with possible Zika virus infection during pregnancy.³ The updated recommendations call for pediatric healthcare providers to assess risk of congenital Zika virus infection, to communicate with obstetrical providers, and to remain vigilant for problems that may develop in infants without birth defects born to mothers with possible Zika virus exposure during pregnancy.

“There’s a lot we still don’t know about Zika, so it’s very important for us to keep a close eye on these babies as they develop,” said Brenda Fitzgerald, MD, CDC Director, in a statement. “Learning how best to support them will require a team approach between healthcare providers and families.”

Progress on the Vaccine Front

Results from two Phase I clinical trials now suggest that an experimental Zika vaccine developed by scientists at the National Institute of Allergy and Infectious Diseases (NIAID) is safe and induces an immune response in healthy adults.⁴

Scientists at the NIAID’s Vaccine Research Center and Laboratory of Viral Diseases have developed the investigational vaccine using a small piece of DNA known as a plasmid. By inserting genes into plasmid to encode two proteins found on the surface of the Zika virus, the researchers create a vaccine that, upon injection, produces a reaction that mimics the Zika virus and sets off an immune response in the body.

Two different plasmids have been developed for clinical testing, labeled as VRC5288 and VRC5283. While they are almost identical, the two differ in specific regions of the genes that might affect protein expression and immunogenicity. With VRC5283 showing the most promise, researchers have moved forward, launching a Phase II trial in March 2017 that aims to vaccinate 2,490 healthy participants in areas of confirmed or potential active mosquito-transmitted Zika infection, including the continental United States and Puerto Rico, Brazil, Peru, Costa Rica, Panama, and Mexico. The two-part trial is designed to assess the vaccine’s safety and ability to stimulate an immune response in participants, as well as determine the optimal dose for administration.

The trial is divided into two parts; Part A will build on ongoing Phase I trials to evaluate further the vaccine’s safety and ability to stimulate an immune response. Researchers plan to enroll 90 healthy men and non-pregnant women ages 18-35 at three sites in Houston, Miami, and San Juan, Puerto Rico, to conduct this section of the study. The second section of the trial, known as Part B, will enroll at least 2,400 healthy men and non-pregnant women ages 15-35. Its focus is to determine if the vaccine can protect effectively against Zika-related disease when someone is exposed to the virus naturally. The study will be based in Houston, Miami, and San Juan, as well as at two additional sites in San Juan, two sites in Costa Rica, and one site each in Peru, Brazil, Panama, and Mexico. Participants will be assigned randomly to receive either the investigational vaccine or a placebo at three separate clinic visits, each four weeks apart.

Participants in the Part B trial will be followed for nearly two years, undergoing assessments for adverse events and symptoms of Zika infection. Researchers will compare the rates of confirmed cases of Zika in the placebo group and the vaccinated group to determine if the investigational vaccine protects against disease caused by Zika infection.

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

REFERENCES

1. Hills SL, Fischer M, Petersen LR. Epidemiology of Zika virus infection. J Infect Dis 2017;216:S868-S874.
2. Reynolds MR, Jones AM, Petersen EE, et al. Vital Signs: Update on Zika virus–associated birth defects and evaluation of all U.S. infants with congenital Zika virus exposure — U.S. Zika Pregnancy Registry, 2016. MMWR Morb Mortal Wkly Rep 2017;66:366-373.
3. Adebanjo T, Godfred-Cato S, Viens L, et al. Update: Interim guidance for the diagnosis, evaluation, and management of infants with possible congenital Zika virus infection — United States, October 2017. MMWR Morb Mortal Wkly Rep 2017;66:1089-1099.
4. Gaudinski MR, Houser KV, Morabito KM, et al; VRC 319; VRC 320 study teams. Safety, tolerability, and immunogenicity of two Zika virus DNA vaccine candidates in healthy adults: Randomised, open-label, phase 1 clinical trials. Lancet 2017; doi: 10.1016/S0140-6736(17)33105-7. [Epub ahead of print].