In a little over 1 year since the Zika virus outbreak began making headlines, a number of drug companies and research institutes have stepped forward to develop dozens of vaccine candidates against the primarily mosquito-borne virus. But it may still be a few years before the first Zika vaccine is available, WHO Director General Margaret Chan, MD, said.
In comments marking the 1-year anniversary of WHO declaring the Zika outbreak in the Americas a Public Health Emergency of International Concern — a declaration that has since been lifted — Chan remarked recently on the nearly 40 candidate vaccines currently in the pipeline but said “a vaccine judged safe enough for use in women of childbearing age may not be fully licensed before 2020.”
WHO spokeswoman Monika Gehner told Infectious Disease News that Chan’s comments are in line with WHO’s official estimate of when a safe and effective vaccine may be ready for women of childbearing age — a critical population to protect because of Zika’s causal association with microcephaly and other serious fetal outcomes.
Anthony S. Fauci, MD, director of the National Institute for Allergy and Infectious Diseases (NIAID) previously told Infectious Disease News that he was “confident” there would eventually be a Zika vaccine, but not before 2018. Fauci’s confidence, he said, was based on previous success against similar viruses.
Gehner also noted previous efforts against other diseases.
“Developing a Zika vaccine is complex,” she said. “Getting a safe and effective Zika vaccine to women of childbearing age could, however, be technically feasible based on experience with vaccine development for other similar viruses, such as yellow fever, Japanese encephalitis and tick-borne encephalitis.”
Zika is primarily spread through the bite of female Aedes aegypti mosquitoes but also can be sexually transmitted by both men and women. Gehner said men of reproductive age would be a second target population for a Zika vaccine, if resources permit.
Anthony S. Fauci
Fifty-nine countries have reported mosquito-borne Zika virus transmission since 2015, including the U.S., where local infections have occurred in Florida and Texas. Thousands of cases of microcephaly and/or central nervous system malformations have been linked to the disease, most notably in Brazil.
Typical vaccine development can take a decade or longer. Currently, there are 39 Zika vaccine candidates in development around the globe, according to WHO tracking. Five of them have either entered or are about to enter a phase 1 trial, Gehner said. These include efforts by the NIH, Walter Reed Army Institute of Research (WRAIR) and United States manufacturer Inovio Pharmaceuticals, whose experimental DNA vaccine, GLS-5700, was the first approved for clinical trials last June.
The NIAID launched two phase 1 trials last year investigating two Zika virus vaccines, including a DNA-based vaccine and an inactivated virus vaccine in collaboration with WRAIR, which used the same technology to successfully develop a vaccine for Japanese encephalitis.
“In terms of prevention, we may not remain so empty-handed for long,” Chan said in her remarks. In addition to the search for a vaccine, she said a number of countries have piloted innovative approaches to mosquito control to combat spread of the disease.
“We are now in the long haul and we are all in this together,” she said. “WHO's strategic planning and commitment to work with partners for sustained interventions and research should go a long way toward bracing the world for this challenging — and still heart-breaking — effort.” – by Gerard Gallagher
WHO. Zika situation report. 2017. http://apps.who.int/iris/bitstream/10665/254507/1/zikasitrep2Feb17-eng.pdf?ua=1. Accessed February 9, 2017.
WHO. Zika: we must be ready for the long haul. 2017. http://www.who.int/mediacentre/commentaries/2017/zika-long-haul/en/. Accessed February 9, 2017.
WHO. Vaccine pipeline tracker. 2017. https://docs.google.com/spreadsheets/d/19otvINcayJURCMg76xWO4KvuyedYbMZDcXqbyJGdcZM/pubhtml#. Accessed February 9, 2017.