Zika virus is an emerging disease caused by a Flavivirus. The virus is predominantly transmitted through the bite of the Aedes egypti mosquito, which inhabits much of the southern United States, as well as tropical and subtropical areas in Central America, the Caribbean, South America, Africa, the Pacific Islands, and Asia. The virus can also be transmitted through vaginal, anal, and oral sexual activity; through blood transfusions; and from mother to fetus during pregnancy. Infected persons can infect others even when they are not symptomatic, and it is unknown how long ZIKV can survive in a host.
Zika virus often does not present symptoms in adults who are affected, but the 20% of infected persons who do become symptomatic most often experience fever, rash, headache, joint pain, pinkeye, and/or muscle pain. According to the US Centers for Disease Control and Prevention (CDC), there have been over 41,000 symptomatic cases reported in the United States since 2015.
Although adult symptoms of ZIKV are relatively mild, ZIKV can be extremely harmful to a developing fetus if a pregnant woman is exposed. Zika virus exposure can result in fetal death, microcephaly, and other abnormalities that are collectively known as Congenital Zika Syndrome. The report notes that congenital Zika syndrome presents difficulties for both the mother, who often faces emotional distress and stigma while dedicating time and resources to caring for her affected infant, and the child, who often requires continuous medical care and may not gain full functional abilities.
Although nearly 40 vaccine candidates are currently under development, there is currently no approved medication or vaccine available for ZIKV treatment or prevention. However, experts believe that the wide range of categories of ZIKV vaccine candidates—namely, whole inactivated viral vaccines, subunit vaccines, nucleic acid vaccines, live attenuated virus vaccines, and viral-vectored vaccines—and the previously safe and efficacious use of some of these vaccine types in other vaccinations for pregnant women means that a ZIKV vaccine could be created that would be safe for pregnant women to receive.
If developed and approved, experts think a vaccination given to pregnant women will likely prevent both maternal ZIKV infection and in utero exposure to the fetus, as do other vaccinations administered during pregnancy. Because of the dual protection offered by most vaccines, the CDC now recommends many vaccinations for pregnant women, and the CDC’s Advisory Committee on Immunization Practices states that the benefits of vaccinating pregnant women usually outweigh the potential risks.