The Zika virus that has caused an epidemic of birth defects in parts of Latin America and the Caribbean receded from the headlines here in the US once cooler weather rolled in last fall. But, as certain parts of the country gear up for mosquito season, public health officials are reminding residents and travelers to prepare and take precautions, while forging ahead to develop the first vaccine to protect against the virus. Zika typically causes only mild symptoms, but the virus can cause several serious birth defects when pregnant women become infected and pass the virus to the fetus.
The National Institutes of Health (NIH) has launched a two-part vaccine study with the goal of enrolling more than 2,000 participants in Texas, Florida, Puerto Rico, and five other at-risk countries. The first volunteer received the experimental vaccine two weeks ago at the Baylor College of Medicine.
The experimental vaccine is very different from traditional vaccines, where a dead or weakened virus is injected into a person to train the immune system to recognize and fight the infection. The experimental Zika vaccine is DNA-based: It is made with a piece of DNA carrying genes from the Zika virus. Currently, there are no DNA-based vaccines approved for human use in the US.
Once injected into the body, the DNA makes particles that resemble Zika so the body can learn to fight it, but cannot cause infection. The experimental vaccine has cleared safety studies and produced a strong immune response in 40 people in the first phase of testing. This phase of the study is testing the appropriate dosage in 90 participants. Once researchers decide on the dosage, the next phase, which will begin this summer, will be to test the vaccine in a larger population. Researchers will track the volunteers for two years to see if there is continued protection from the virus.
Analysis: As of the end of March, the US Centers for Disease Control and Prevention (CDC) is reporting more than 5,000 cases of Zika virus in the US. Most of these cases are from travelers returning from other affected countries, while just over 200 appear to be acquired through local mosquito-borne transmission in Florida and Texas. Researchers are modeling scenarios to identify high risk areas for Zika transmission in the US in the coming months, based on the presence of Aedes aegypti mosquitos and other factors, including the number of women of child-bearing age, and focusing on surveillance, mosquito control, and prevention education.
In addition to the DNA-based vaccine, the NIH is testing the safety of some more traditional Zika vaccine candidates as well. The DNA vaccine was the first ready to advance to this second stage of human testing. DNA-based vaccines may have significant advantages over traditional vaccines. They have the potential to more closely resemble parts of the virus that are altered by manufacturing of live attenuated or killed viruses and could be more effective at stimulating an immune response. DNA-based vaccines also have the potential to be safer than live virus vaccines, especially in immunocompromised patients. Finally, DNA-based vaccines may be designed to include genes against several different pathogens and could decrease the overall number of vaccines necessary to fully immunize children.
This weekly series explores innovative breakthroughs and new technologies that are driving momentum and change in the life sciences and health care industry.