No Zika vaccine in sight, but modified yellow fever virus vector could speed development

Zika is an RNA virus transmitted to humans by Aedes ​mosquitoes. ​Until recently it was thought to be relatively harmless with only 20% of infections resulting in mild, short-lived symptoms such as rash, headache and conjunctivitis.

However, a PAHO​ report linking the current South American Zika outbreak to an increase in the number of microcephalic babies born in Brazil and Guillain–Barré syndrome (GBS) cases in El Salvador​ has prompted a reassessment.

Authorities in Columbia​, El Salvador and Jamaica​ where the number of Zika cases is increase have recommended that women delay getting pregnant. The US CDC has advised​ pregnant women to consider postponing travel to affected countries.

According to reports​ three travellers who returned to the UK from South America have been diagnosed with Zika virus. The CDC has also confirmed cases​ in several US citizens who have recently been in the region. 

No vaccine​

At present there is no vaccine against Zika.

Current prevention​ efforts are focused on eradicating the mosquitoes that transmit the virus to people, which is a significant challenge in the tropical and sub-tropic regions hit by the current outbreak.

Andrew Easton from the University of Warwick predicted that the severity of the conditions to which Zika has been linked will increase drug industry interest in vaccine development. He suggested that efforts could focus on modification of vaccines for related diseases.He told us “Zika belongs to a family of viruses, the Flaviviridae, which includes a number of other viruses of concern such as dengue, Chikungunya and as a more distant ‘relative’ yellow fever virus. ​

“There are some possibilities that will probably be explored such as using the yellow fever virus vaccine, or possibly a vaccine from a completely different type of virus, as a vehicle to carry the necessary parts of Zika virus to promote an immune response​.”

But a Zika vaccine is not likely to be available soon – certainly not before Brazil plays host to the Olympic Games​ this summer – according to Easton.

“Making a vaccine by the conventional route is very slow and by no means guaranteed to work in a time frame that would be useful for the current situation​” he said, adding “there is also the question of passing the normal regulatory tests and requirements for safety and efficacy which normally take some time​.” 

Development news​

Another option is to use DNA technology according to South Korea based GeneOne Life Science, which announced it is conducting preclinical research on a candidate Zika vaccine in partnership with US firm Inovio Pharmaceuticals.

The firms, which are also collaborating on clinical trials of trials of an Ebola vaccine candidate called INO-4212 and a MERS vaccine called GLS-5300 – said the immunogenicity of the Zika vaccine is being tested in animal studies.

GeneOne and Inovio did not respond to a request for comment.