Zika virus (ZIKV) is a flavivirus that is responsible for an epidemic in Brazil and the Americas. ZIKV has been causally linked with fetal microcephaly, other birth defects in humans, and intrauterine growth restriction.
Two different ZIKV vaccine candidates have just been shown to provide complete protection in mice against a ZIKV strain from Brazil. A research team led by scientists at Beth Israel Deaconess Medical Center (BIDMC), together with colleagues from the Walter Reed Army Institute of Research (WRAIR) and the University of Sao Paulo, published their results in the journal Nature.
A DNA vaccine developed in the Barouch laboratory at BIDMC, and a purified inactivated virus vaccine developed at WRAIR were tested.
A single immunization of a plasmid DNA vaccine or a purified inactivated virus vaccine provided complete protection in mice against challenge with a ZIKV outbreak strain from northeast Brazil. This strain crosses the placenta and induces fetal microcephaly and other congenital malformations in mice.
Mice were vaccinated with these vaccines and 4 weeks later were injected with the Zika virus. All vaccinated mice were protected from ZIKV. Complete protection also occurred in mice exposed to infection eight weeks later.
The vaccines elicited antibodies which protected against the Zika virus. The Zika-specific antibody levels detected in the mice correlated with protection against infection.
Researchers are hopeful that an effective human vaccine can be developed based on these results.
Dr. Barouch said, “The explosion of the current ZIKV outbreak and the devastating clinical consequences for fetuses in pregnant women who become infected demand the urgent development of a ZIKV vaccine. The effectiveness of these vaccines, the clarity of the antibody protection and the similarity to successful vaccines that have been developed for other flaviviruses provide substantial optimism for a clear path forward for the development of a safe and effective ZIKV vaccine for humans.” Clinical trials to test these vaccine candidates are expected later this year.
The vaccine won’t be developed in time for the Olympics in Brazil. Pregnant women should avoid areas with Zika virus epidemics.
Flaviviruses also include West Nile virus, yellow fever virus, Japanese encephalitis virus, tick-borne encephalitis virus, and dengue viruses. Effective vaccines against these diseases have been developed.
The CDC states that Mosquitoes that spread Zika virus bite mostly during the day. Wear long-sleeved shirts and long pants to protect yourself. Stay in hotels and homes with air conditioning and window and door screens.
Use a mosquito bed net if you are overseas or outside and can’t protect yourself from mosquito bites.
Use Environmental Protection Agency (EPA)-registered insect repellents with one of the following active ingredients: DEET, picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol. Choosing an EPA-registered repellent ensures the EPA has evaluated the product for effectiveness. EPA-registered insect repellents are proven safe and effective, even for pregnant and breast-feeding women.
The CDC states, “Do not spray repellent on the skin under clothing. If you are also using sunscreen, apply sunscreen before applying insect repellent. Do not use products containing oil of lemon eucalyptus or para-menthane-diol on children younger than 3 years old. “
These steps will help prevent Zika infection but do not guarantee you will be safe. The only way to do that is to completely avoid areas with infected mosquitos.