The World Health Organisation (WHO) has changed Zika’s status from emergency of international concern to a long-term problem. However, with all proposed vaccines currently in Phase I of clinical trials, researchers do not know if Zika was just a one-off disaster or if it will become an annual threat, posing implications for vaccine development.

A delay in the outbreak or no outbreak at all could set back when the vaccine becomes commercially viable, by years.

“On one hand, you don’t want to see outbreaks of infection,” said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at America’s National Institutes of Health (NIH).

“But on the other hand, [without that testing] you might have to wait a long time to make sure that the vaccine works,” he added.

A race against outbreaks for vaccine development

“If we don’t get a lot of infections this season in South America and Puerto Rico, it may take years to make sure the vaccine works,” said Fauci.

Thus far, the climate suggests weather will be ripe for Zika as the higher temperature increases the voracity of the Aedes aegypti mosquito, the main transmitter of Zika. These mosquito population numbers are being closely monitored in the United States and Mexico since heavy movement across the border can increase the likelihood of transmission.

However, despite a warmer-than-usual winter, mosquito numbers have been low, with no sign of Zika.

“There’s so many factors that go into it, it’s really impossible to make an ironclad prediction,” said Chris Van Deusen, spokesman for the Texas Department of State Health Services, which is doing much of the monitoring.

Researchers say they are keen to prevent a repeat from the Ebola outbreak of 2014, in which the outbreak was brought under control before many of the trials could take place.

“All of us felt like we kind of really missed the boat with Ebola,” says Nelson Michael, director of the US Military HIV Research Program at the Walter Reed Army Institute of Research.

Unpredictability may affect research funding

There is also concern that the delay could lead the private sector to withdraw its funding and given the costs to develop medications, this could prove fatal. With competing interests, if the vaccine is difficult to test, investors’ attention will turn elsewhere.

For pharmaceuticals companies, there is also the risk that the vaccine may only be used during outbreaks. “That’s something we talk about a lot,’’ admitted Jon Heinrichs, associate vice president and project lead for Sanofi Pasteur, the only pharmaceutical giant with plans of producing a Zika vaccine in the near future.

“We have models that suggest there is no profitability for this vaccine, and we have models that suggest it could be profitable. Time will tell,” he added.

Researchers from NIH’s National Institute for Allergy and Infectious Diseases and the Walter Reed Army Institute of Research, proposed injecting volunteers with the Zika virus as an alternative vaccine testing method.

However a federally appointed ethics panel at the NIH panel advised against it, stating that it was currently unethical because of the study’s capacity to harm third parties, such as the sexual partners of volunteers.

Zika epidemiology is still understudied

Even as medical understanding of the transmission of the virus increases, there is still little knowledge about what to expect from the virus because there is little information about the circulation of Zika around the world.

One theory suggests that the virus will spread frequently around Asia and Africa, infecting most when they are children and leaving women immune by the time they start to have babies. If that is true, then the issue of Zika birth defects may become very rare once that pattern is established in Latin America.

“The problem is we don’t really understand the epidemiology of the virus,” said Heinrichs.

“Will the market include Latin America, Asia, Africa, and potential for the US and Europe? Or will be limited to stockpiling in case of future epidemics?” he added.

Either way, the irony remains that without another epidemic, researchers have no way of knowing. MIMS

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