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First Human Trial of New Zika Vaccine Begins

The first participant has received a dose of a new Zika virus vaccine being trialled by Liverpool researchers.

Although Zika is now not as prevalent as during its peak in 2016, it remains an ongoing threat, with thousands of cases of the mosquito-borne virus reported each year, mainly in countries close to the equator. The virus has been reported in Africa, Asia, Australia and the Pacific region, Caribbean, Central America, South America, and North America.

Zika virus does not naturally occur in the UK and almost all UK cases are associated with travel to countries or areas with active Zika virus transmission.

Currently, there are no approved Zika vaccines or treatments available anywhere in the world.

Dr Richard Fitzgerald, clinical research facility director, Royal Liverpool University Hospital and associate consultant in clinical pharmacology and general internal medicine, said that the "ground-breaking" trial aims to find a vaccine that will protect current and future generations against the devasting effects of the Zika virus.

Pregnant Women Particularly At Risk

In its most recent update in February 2019, Public Health England reported there had been 314 travel-associated cases of Zika – and one likely sexually transmission case – between 2015 and 2018. The majority of Zika cases in the UK had travelled to the Caribbean and South and Central America, Public Health England said at the time.

In 2018, in the UK four travel-associated cases were diagnosed, including two cases with virus detected and two cases with antibody evidence.

For most people, Zika virus causes a very mild infection and no long-term problems. However, it may be harmful in pregnancy as it can lead to complications and birth defects in the baby, in particular, microcephaly.

"Pregnant women continue to be the population at highest risk for the infection as the virus can cause severe foetal birth defects," said the researchers behind the new trial, who hoped that the vaccine, designed to be suitable for use during pregnancy, would generate "highly protective and long-lasting immunity". 

Zika 'Should Not Be Forgotten'

Having shown promising results in animal studies, the vaccine has now moved into a 'first in human' phase I trial, explained the researchers. 

Healthy volunteers recruited to the trial will receive two doses of the new vaccine to evaluate its safety, tolerability, and ability to produce an immune response. 

Over the next 9 months, up to 40 volunteers will be involved in this phase of the randomised controlled clinical trial, with the vaccine assessed in groups of four volunteers at a time, numbers increasing as evidence of safety accumulates, explained the researchers. 

In addition, the performance of the vaccine would also be assessed in people who have had exposure to other viruses that circulate in the places where Zika virus is found, such as dengue virus, or people who have had the yellow fever vaccine, highlighted the researchers.

Project lead Professor Neil French, director of the Centre for Global Vaccine Research at the University of Liverpool and honorary consultant in infectious diseases at Royal Liverpool University Hospital, said that the vaccine being trialled was the first of several vaccines that were moving from laboratory concept to human use.

"Zika should not be forgotten, especially since climate change is contributing to the spread of the Aedes mosquitoes (the mosquitoes that can carry the Zika virus) to countries where immunity is not there", cautioned research fellow, Dr Krishanthi Subramaniam. "Vaccines like ours will enable us to be better prepared for the next Zika outbreak," she said.

"The pandemic taught and continues to teach us that infectious diseases are a global issue, but with the help of vaccines we can make great strides in keeping everyone safe," she believed.