The National Institutes of Health announced clinical trials for a live Zika vaccine this month, one of five vaccine candidates currently under development by the agency. “Zika virus infection remains a significant threat to pregnant women and their developing fetuses, and we can expect to see periodic outbreaks and cases in areas where Aedes aegypti mosquitoes thrive,” […]
The National Institutes of Health announced clinical trials for a live Zika vaccine this month, one of five vaccine candidates currently under development by the agency.
“Zika virus infection remains a significant threat to pregnant women and their developing fetuses, and we can expect to see periodic outbreaks and cases in areas where Aedes aegypti mosquitoes thrive,” said Anthony S. Fauci, M.D., director of NIH’s National Institute of Allergy and Infectious Diseases. “NIAID remains committed to developing safe and effective Zika vaccines, and we are pleased to begin clinical testing of a live attenuated candidate.”
By combining genes from multiple viruses, researchers led by Stephen Whitehead, PhD. at NIAID, created a hybrid virus that is live but weakened to prompt an immune reaction without causing side effects.
Fauci added that live-virus vaccines have historically provided a “robust” and “durable” response from the human immune system.
The vaccine, known as rZIKV/D430-713, will enter Phase 1 clinical trials, consisting of 28 healthy non-pregnant adults aged 18-50 at The Johns Hopkins Bloomberg School of Health Center.
Fauci explained that Phase 1 trials are designed to assess the vaccine’s safety and expected response from the human immune system.
Should the vaccine perform well in Phase 1 trials, it will move on to Phase 2 trials, which will include a larger sample size to “determine the precise nature of the response” and get the right dosage along, with additional safety data, according to Fauci.
From Phase 2 trials, the vaccine would then move on to Phase 3 trials, with multiple large samples of test subjects of varying numbers to evaluate the overall effectiveness of the vaccine in large population settings.
Since the 2015 outbreak, which affected numerous countries in Central and South America, Fauci explained, there are continued “minor outbreaks” in Asia and Africa with very little Zika activity in the Western Hemisphere.
In addition to rZIKV/D430-713, NIAID currently oversees the evaluation of five other candidate substances for a Zika vaccine, all at various stages of development.
Developed by NIAID researchers and known as VRC 705, the vaccine is designed to arm the human cells with DNA engineered to combat the virus. In 2017, NIAID launched Phase-2 trials for the vaccine.
NIAID is also closely cooperating with the University of Pennsylvania, along with pharmaceutical companies GlaxoSmithKline and Moderna/Valera, to develop an mRNA vaccine designed to trigger a response in a person’s RNA as opposed to DNA. In 2017, the vaccine underwent animal trials in mice.
Undergoing early pre-animal tests, NIAID researchers are also developing a modified version of a Vesicular Stomatitis Virus (VSV) vaccine, a flu-like disease that affects cattle. Another version of a VSV vaccine for Ebola underwent tests in animals.
The Walter Reed Army Institute of Research is conducting Phase-1 trials in 2018 of an inactivated vaccine, known as ZPIV, which consists of a dormant version of the virus designed to train the immune system to react to a potential infection.
London-based pharmaceutical companies SEEK and hVIVO also are currently developing a vaccine, known as AGS-v. Rather than trigger an immune response to a specific virus, the substance provides a broader defense, which triggers responses to mosquito saliva. In 2017, AGS-v underwent Phase-1 trials.
Fauci said it was “way too early” to say predict which of the six candidates would eventually be selected as a Zika vaccine.
Although most people experience only mild illness or no symptoms when infected with Zika virus, babies born to women infected with Zika virus during pregnancy may have birth defects and/or develop health problems in their early years.
Zika virus is primarily transmitted to humans through the bite of an infected mosquito or can be transmitted through sex. The CDC advises that pregnant women should not travel to areas with a risk of Zika and also recommends that partners of pregnant women and couples considering pregnancy should know pregnancy risks and take certain precautions, such as taking steps to prevent mosquito bites, engaging in safe sex practices, and talking to a doctor or healthcare provider after traveling to an area at risk for the Zika virus.
The U.S. Zika Pregnancy and Infant Registry has recorded the number of pregnant women with laboratory evidence of possible Zika virus infection since 2015.
As of 2018, the Maryland Department of Health recorded three Zika cases in the National Capital region, which includes Montgomery, Prince George’s, and Frederick Counties.