As more evidence connects the Zika virus to Guillain-Barré syndrome, stillbirth, miscarriage and other birth abnormalities besides microcephaly, researchers have realized the effects documented thus far may have just been the tip of the iceberg.
Currently, public health officials are using every preventative measure they have access to, including using mosquito repellent, controlling mosquito populations, putting screens on windows, and educating communities about how to protect themselves – but it simply isn’t enough.
Labs and research teams across the globe are scrambling to create a vaccine for Zika, but that’s a lot easier said than done.
Although little is known about Zika, we can look to its family, Flaviviridae, for insight. Flaviviridae is a family typically found in arthropods, like ticks and mosquitos, but they can occasionally infect humans. And when they do, they’re dangerous. You’ve probably heard of some of Zika’s closely related viruses, like Yellow Fever, Dengue Fever, Japanese Encephalitis and West Nile Virus.
To put it in perspective, the dengue virus – a potentially fatal mosquito-borne virus that causes hemorrhagic fever – is approximately 40 percent homologous to the Zika virus on the amino acid level. It took researchers 20 years to develop a vaccine for dengue virus, and this vaccine is still not considered highly safe or effective.
The basic idea behind a vaccine is simple: expose healthy people to a harmless form of a virus. Creating one, however, is anything but. Vaccines that work wonders in animals can prove useless in humans. Vaccines that appear safe in human trials can create side effects no one saw coming. It generally takes about two decades to make a vaccine, and Zika wasn’t on anyone’s radar until April of last year.
Currently, some researchers are using a similar approach to the one used for West Nile – a DNA approach, which involves taking DNA from the virus, inserting it into a plasmid, and allowing the plasmids to replicate in a host. When plasmids replicate they don’t actually produce virus particles – they produce what researchers call ‘virus-like particles,’ which triggers an immune response without creating the effects of the virus in the host.
Other researchers are using an approach similar to the dengue vaccine. This involves exposing the host to a live, but attenuated (weakened) version of the virus. This approach typically elicits a strong immune response in the host, but can be dangerous for individuals with weakened immune systems.
Some labs are working on creating an inactivated vaccine, an approach that involves injecting a host with a killed version of a virus. Because the virus is dead it cannot replicate, but it can still trigger an immune response when the body recognizes it.
Even if one type of vaccine proves effective, we would ideally want to have as many vaccine options as possible. For example, pregnant women – the population most heavily impacted by Zika – are contraindicated (advised not to take) live or live attenuated vaccines.
On the other hand, live attenuated vaccines are generally the most effective kinds of vaccines. They are typically so effective, that they would likely be indicated for anyone planning to get pregnant as well as their significant others.
No matter how many people we have working on a Zika vaccine, a large-scale, human-based trial could still be years away. And even if the vaccine does make it to human trials, it could hit any number of regulatory and commercial hurdles before actually making it to market.
