Is There a Zika Virus Vaccine?

8 Facts About the In-Testing Vaccine

medical research in lab
Victor Torres/Stocksy United

There's a Zika vaccine being tested, but we don't know yet if it will be good enough. We don't know if it will help stop what was a public Health Emergency—the Zika outbreak that has rapidly spread in Latin America and elsewhere.

A Zika vaccine may be able to help stop the spread of this virus. The infection has been tied to microcephaly and other birth defects in children born to mothers who were infected while pregnant.

Here are eight things to know about one potential Zika vaccine in progress.

1. The Vaccine Isn't Ready Yet, but It's in Testing

One Zika vaccine, called GLS-5700, was developed by the work of two companies—Inovio in Pennsylvania and GeneOne Life Science in South Korea. They received approval from the FDA to begin testing in people and testing is planned to start in August 2016.

The vaccine has been tested in monkeys and mice. It was tested in these animals with two doses either injected into their muscles or skin.

The version of the vaccine to be tested will be a intradermal (or skin based) vaccine. It wouldn't be as deep an injection as the intramuscular shots we often get.

2. The First Vaccine to Be Studied Is a DNA Vaccine

A DNA vaccine is less common. This type of vaccine was first developed for animals—a vaccine for West Nile was first licensed in horses. The West Nile DNA vaccine has been studied in people, but has not been licensed in people, but there is one DNA vaccine used in people in Australia for Japanese Encephalitis, but again, there are none licensed for people in the United States.

A DNA vaccine uses tiny bits of DNA in order to create an immune response. This immune response is created passively. These vaccines create this response by introducing a plasmid that has a DNA sequence that encodes an antigen (or antigens) that can elicit an appropriate immune response. The vaccine relies on the production of the target antigen from this DNA in the person who has been vaccinated.

Zika, by the way, is an RNA virus. This doesn't matter. It's the antigen that is encoded that elicits the immune response to Zika.

3. A DNA Vaccine Can Have a Lot of Advantages

  • It can create different types of immune responses. We have different cells that can create different types of immune responses. This sort of vaccine can create both a B and T cell response.
  • The vaccine can be more stable for storage. They aren't affected by changes in temperature. This matters since Zika spreads where mosquitoes are, which is where it is warm. Diseases also can spread in areas where electricity isn't constant and can go off or where specific temperature fridges aren't available to maintain "cold chain" to transport vaccines to clinics. It also just makes it easier if you don't have to worry about keeping a vaccine at a certain temperature. Less hassle, less cost, and vaccines will be easier to give.
  • The vaccine doesn't involve any sort of infectious pathogen. The whole virus isn't used. There isn't a weakened virus that's alive (a live attenuated virus). There isn't a killed virus. There are just pieces of DNA. So although other vaccines have been quite safe with killed virus or live attenuated virus, no one has to worry about there ever having been an infectious virus in this vaccine.
  • It's easy to manufacture on a large-scale. This will help with future epidemics of other pathogens as well. If we can quickly respond with a DNA vaccine to Zika, we will know how to more quickly scale up a response to other new pathogens.
  • It's possible, at least in horses with another DNA vaccine, to distinguish immune response from those vaccinated from those infected. This helps track how the virus has spread - and whether the vaccine is successful.

4. The Vaccine Has a Unique Way of Being Injected

The vaccine is administered with a tiny electric zap. It may be administered through the skin (or even as an injection into muscle).

 The vaccine is then given with this electrical pulse so that the DNA in the vaccine can make it into cells. This is called electroporation. With the help of this zap letting the DNA into cells, the immune system can start mounting a response.

5. This Vaccine Is Far From Being Ready to Be Sent Out to Patients

This vaccine is cleared for Phase I testing, which may sound exciting, but this is just the first of three phases of testing, which are then followed by even more regulatory and licensing steps before any vaccine would be available worldwide.

Phase I testing allows us to know if a vaccine or drug seems safe. It is tested in a small number of healthy volunteers at increasing doses to see if it is safe and well tolerated at these increasing doses.

Afterwards, if the drug seems safe and tolerated, Phase II testing will start to see if the vaccine or drug is effective. In Phase II, a limited number of patients are given the drug to see how tolerated, safe, and effective it seems.

If the drug continues to come across as safe, Phase III testing will further assess how efficacious the vaccine or drug is in ideal settings and effective in real world situations. Phase III testing will distribute the drug to even more patients to test safety, efficacy, and effectiveness in a larger trial.

Even if the vaccine is found to be safe and effective, it would still need to pass more regulatory steps. The vaccine then has to be licensed by governments. If all goes well, the WHO could also determine whether a vaccine as produced by a manufacturer is prequalified for use.

6. There Are Multiple Potential Vaccines

There is work on multiple DNA vaccines. These vaccines can use different stretches of DNA. Some may target specific proteins.

These multiple vaccines will then be tested to see if they create antibodies and immune responses which we expect to protect us from Zika.

7. It Will Need to Work During Pregnancy

Zika affects pregnancies, which poses a problem.

Pregnant women can respond to infections differently. They may be more susceptible or infections may last longer during pregnancy. Their immune systems may behave differently. Moreover, their children, when born, can be affected by illnesses that barely affected mom.

Additionally, many pharmaceutical and regulatory agencies are reluctant to test vaccines and drugs on pregnant women, for fear of effects on the fetus.

We also don't know exactly how Zika can affect a fetus and what its full range of effects. We don't know how much the placenta can be affected, which means that there is much to be learned that could play a role in the development of the vaccine.

8. What We Don't Know Can Influence Vaccine Production

There's still a lot we need to learn about Zika. Does Dengue make Zika worse? Does our immune response, like with Dengue, make Zika worse? Are some people more vulnerable to Zika? How long does Zika last in pregnant women? How long does it last in sperm?

Answers to these questions and more could determine how vaccines help us fight Zika, and affect the production of the vaccine. While there is still a lot to learn, experts are making progress, and hope for a functioning vaccine is high.

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