Zika virus importation and the ‘Bolt’ race against Zika (A perspective piece from the press release held at the 16th ICI Conference, 2016, Melbourne)

August 24, 2016 – 16th International Congress on Immunology (ICI) Conference, Melbourne, Australia

By Dr. Chibueze C. Ezinne MD., Ph.D

Bagging a host of awards, Olympians, Paralympians and tourists alike are returning home from Brazil, the focal point for Zika virus (ZIKV) spread. The potential for epidemic spread raises suspicions on what travelers may be lugging home and a need for speeding up preventive strategies.

This situation is against the background of the written media release from the CDC on August 12, 2016, which stated that “18 countries currently not reporting ZIKV outbreaks have the environmental conditions and population susceptibility to sustain mosquito-borne transmission of Zika virus if a case were imported from infection at the Games”. Moreover, among the 206 participating countries, “39 have CDC travel notices indicating an ongoing Zika virus outbreaks or epidemics”. It’s noteworthy that all the 206 participating countries are at risk for travel-associated importation of ZIKV.

ZIKV belongs to a family of flaviviruses and is transmitted by mosquitoes of the Aedes aegypti species. Infection with ZIKV results largely in fever, joint pain, and rash. Zika was declared a public health emergency of international concern (PHEIC) on February 1, 2016, by the World Health Organization (WHO) due to associations with neonatal abnormalities observed in ZIKV-infected pregnant women. Sexual transmission of ZIKV has also been reported.

As a potential preventive strategy, the development of vaccines against ZIKV is needed. The mechanism of induction of human ZIKV infection is still largely unknown, and this understanding is crucial to the development of clinical trials which can be translated to human vaccine production.

Immunologists have risen to the ‘Bolt’ race challenge. At the press conference for the 16th International Congress of Immunology (ICI) held on August 24, 2016, Professor Jorge Kalil of the Butantan Institute and President of the International Union of Immunological Societies, discussed efforts to translate research on dengue (same family of flaviviruses as ZIKV) to the production of vaccines against ZIKV.

Based on a research conducted in collaboration with the National Institute of Health (NIH) and the Biomedical Advanced Research and Development Authority (BARDA), they had to consider a vaccine that can withstand the cold chain storage process, rapidly move through the regulatory process and be given to at-risk populations (pregnant women and non-pregnant women), with the potential for Zika virus transmission to newborns. Therefore, the choice of inactivated vaccines (dead viruses used to produce neutralizing antibodies) seems reasonable.

Phase 2 clinical trials aiming to test the safety and ability of the vaccines to induce an immune response are ongoing. Prof Kalil, however, noted a challenge common to clinical trials, an imprecise timeline for the end-product, in this case, a vaccine. He made this clear in his words:

“We are going to do everything that we can to have it in 3 years, though we don’t know if it will be useful in 3 years.”

“He then continues, “We think that the spread will be around for 3/4 years and then disappear, so if we want to do something for the women that may get pregnant during this period, we have to be very quick. In order to be very quick, we should not try to develop vaccines that may take a long time to be approved by regulatory authorities, so that is why we have to work on inactivated vaccines.”

The 3 to 4-year forecast for Zika virus vaccine development comes from mathematical models which assume that a large population will get immunized after the infection, and once a critical threshold is attained (probably over the 3 to 4 year period), the likelihood of further transmission of infection will be significantly reduced. Unlike dengue, the absence of a serotype for Zika adds to the challenge of vaccine development.

The question then is, will the vaccine still be useful?

Well, the answer is Yes.

“The babies who will be born over the coming 10-15 years increase the number of ‘susceptibles’ who might, in turn, reignite a wave of transmission thereafter”

“The babies who will be born over the coming 10-15 years increase the number of ‘susceptibles’ who might, in turn, reignite a wave of transmission thereafter,” Prof. Kalil explains. Administration of the vaccines when ready can still help to prevent this possible second wave of transmission, he further admits.

Professor Cameron Simmons of the Peter Doherty Institute for Infection and Immunity encouraged the use of other control strategies such as vector control and personal protection. He dismissed the suggestion of avoiding pregnancy for the next four years.

Another question – Should you/we be scared?

Prof. Cameron dismissed such fears saying, “public health response to arbovirus transmission is very aggressive as has been seen with outbreaks such as dengue in France.” However, he noted a risk for exportation to other countries with a high probability of association with seasonal variations, mostly during summertime.

Photo credits: Olympics Games Rio 2016

Press Release: Chibueze C. E (Ruth) attended this press conference held at the 16th ICI Conference in Melbourne as a presenter and an independent medical journalist.