Health

Human trial of Zika vaccine to start soon

The first Phase-1 human clinical trial of a vaccine for the Zika virus is set to begin in the coming weeks, with the U.S. Food and Drug Administration (FDA) green-lighting it. The DNA vaccine (GLS-5700) developed by the U.S-based Inovio Pharmaceuticals and GeneOne Life Science, South Korea, has already been tested on animals and found to elicit “robust” antibody and T cell responses.

The human trial will be carried out on 40 healthy adults to evaluate safety, tolerability and immunogenicity and the interim results are expected before the end of the year. But it may take a couple of years to know if the vaccine works against Zika. According to the World Health Organization (WHO), four of the 14 companies working on a candidate vaccine have reached the preclinical stage.

It is a remarkable achievement to be in a position to carry out clinical trials on humans as the time taken to develop the experimental vaccine has been shrunk significantly. Though the current Zika outbreak began in Brazil in May 2015, the impetus and urgency to develop a vaccine came about only after February 1, 2016 when the WHO declared Zika as a global public health emergency of international concern.

Lessons from Ebola

A major lesson learnt from the Ebola epidemic is the overwhelming need to start vaccine trials quickly. Large-scale trials of the vaccine suffered as they began about a year after the outbreak was first reported and just as the number of people infected was reducing.

As of June 15, the Zika virus has already spread to 60 countries and territories. Even as it spreads geographically, there has been a decline in cases of infection in some countries or in some parts of countries. It is unlikely that vaccine trials may suffer for want of infected people. “At this stage, WHO does not see an overall decline in the outbreak,” the June WHO situation report says.

Yet, Zika vaccine development faces a huge hurdle that the Ebola vaccine did not. The candidate Zika vaccine has to be tested on pregnant women as some babies born to women infected with the virus during pregnancy suffer from microcephaly. Hence, testing a candidate drug/vaccine on pregnant women or women in the child-bearing age can take place only if the vaccine has been found to be very safe in men and non-pregnant women. Also, extensive safety data of vaccinated pregnant women and those about to become pregnant will be required before the vaccine gets approved for commercial use.

While the candidate vaccine that will be tested will be a DNA vaccine, a March 9 report of the WHO clearly states that developing vaccines that use inactivated viruses for use in women of childbearing age or pregnant women will be a research “priority”. Inactivated virus used in vaccines cannot multiply and hence considered safe for use in pregnant women.

As of June 15, 1,581 cases of confirmed microcephaly and other nervous system disorders have been reported in Brazil; microcephaly is yet to be ascertained in another 3,000-odd babies.

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Printable version | Feb 17, 2020 8:44:06 PM | https://www.thehindu.com/sci-tech/health/Human-trial-of-Zika-vaccine-to-start-soon/article14395136.ece

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