Let's talk infectious diseases, the reason for vaccines: ᶻⁱᵏᵃ ⱽⁱʳᵘˢ

The Zika virus is a member of the virus family Flaviviridae and is closely related to other mosquito-borne viruses such as those that cause dengue fever, yellow fever, and Japanese encephalitis. The primary carrier of the virus, the Aedes aegypti mosquito, is unusual in that it is most active during the daytime hours. It only takes one bite for an infection to occur. Once the surrounding skin cells are inoculated, the virus can quickly move into the bloodstream and spread throughout the body.

Zika virus is mainly spread by mosquitoes. The virus can also be transmitted during sex, mostly from men to women as the virus can persist for months in semen.

Zika can also be passed from mother to child during pregnancy and, on rare occasions, through a tainted blood transfusion.

A Zika infection is usually mild and uneventful, but it can turn serious if passed to a developing fetus during the early stages of pregnancy. While scientists do not yet fully understand the pathway of the disease, it appears that the virus is able to breach the placenta during the early part of the first trimester when fetal stem cells are just starting to specialize into the brain, heart, and other vital organs.

The virus' impact on these cells can be devastating, causing serious malformations and increasing the risk of miscarriage and stillbirth. The most serious concern is microcephaly, a rare and irreversible birth defect in which a baby is born with an abnormally small head and brain.

The risk of microcephaly appears to be limited to the first trimester. By the second and third trimesters, the risk will have decreased to near-negligible levels, according to research from the CDC. Still, babies born to mothers with Zika can have serious neurological issues regardless of the trimester she was infected.

While discovered in 1947, Zika virus (ZIKV) remained unimportant and unnoticed until the Yap Island outbreaks in 2007. Even then, it scarcely raised interest and concern quickly abated as the outbreak dwindled without further outbreaks occurring. This situation changed dramatically with the unexpected and large outbreaks that began in 2015 in Brazil—eventually resulting in an estimated 200,000 identified cases. As a result, the world has had to play “catch-up” by rapidly investigating ZIKV immunology, pathophysiology, and its short- and long-term effects, as well as the full spectrum of pathology the virus may cause in different populations.

As of 2021, there is no effective drug to treat—or vaccine to prevent—Zika infection. As of 2019, some 18 known vaccine candidates are in various stages of preclinical and clinical development. A wide variety of formulations are being studied; among those being tested are live virus vaccines, inactivated vaccines, whole-virus vaccines, subunit vaccines, and messenger RNA (mRNA)–, DNA-, protein-, and vector-based formulations.

The ideal vaccine against Zika would require a single dose, be capable of being administered to anyone regardless of age or medical condition (including pregnancy), result in durable (if not lifelong) immunity, prevent medically significant outcomes of infection in both the immediate recipient (eg, GBS) and in the fetus (eg, microcephaly and other congenital conditions), be safe and highly effective, and ideally not require either a cold chain or complex logistics to store and administer. Given the observation of intermittent outbreaks thus far, the ability to store vaccine stockpiles for long periods of time is also necessary.

{You can find all the sources I used by clicking here.}