Last weekend, the 2016 summer Olympics wrapped up in Rio de Janeiro. Hundreds of thousands of people from around the world had descended on the city hoping to see the top athletes from their countries snag a gold medal or two to bring home. But as Simone Biles navigated the balance beam and Usain Bolt dashed toward the finish line, concerns that had been brewing for months regarding the city’s preparedness to host the games were murmured in the stands, the media, and the cafes outside the stadiums. One of these concerns centered around the extent to which the Olympics – and, by extension, the world – would be affected by the outbreak of Zika virus that has affected Brazil and nearby regions for about a year now.
To be clear, while some have argued that Zika virus has been overhyped, the medical community – including the clinical research industry – are taking it quite seriously. Two Phase I clinical trials in search of a vaccine recently commenced, and dozens more are in earlier stages of development, all appearing in the last year.1 The researchers behind the Phase I trials span international borders and both the public and private sector.
But Phase I trials take place years before a compound is actually approved for marketing, and the industry is speculating about what, exactly, the Zika landscape will look like a decade from now. STAT News points out that other recent epidemics that have attracted global attention in recent years – SARS, Swine Flu, and others – didn’t retain their “epidemic” status for long. On the other hand, certain factors give Zika more potential to spread than those other diseases. As the two Phase I vaccine trials move through the later phases and, hopefully, toward FDA approval, will the global impact of Zika virus shrink, be contained, or grow?
The place for a Zika virus vaccine
Of course, diseases don’t simply disappear when an epidemic ends. The 2014 Ebola outbreak was tamed after a few months, but was only the most recent of almost a dozen Ebola outbreaks across Africa since 2000. Malaria, which, like Zika virus, is transmitted by mosquitoes, still hasn’t been eradicated. If Zika follows the pattern of its recent predecessors and fades from headlines in the near future, the market for a vaccine may be limited to a precaution against recurrence, but it will not necessarily disappear.
The recently-approved Phase I Zika trials could also ultimately contribute to the well-established market for region-specific vaccines, such as those for yellow or typhoid fever. And the specific region affected by Zika virus is already bigger than it was just a year ago. Despite the worldwide dissipation of Olympic tourists from an epidemic area, the CDC doesn’t expect this year’s summer games to lead to a significant number of new cases in other regions.2 But in Florida last week, the number of Zika cases originating from bites from local mosquitoes ticked up to 30; hundreds of others in the state have contracted the virus from other means.3
How Zika virus could continue to spread
It’s no coincidence that Florida is the U.S. state where Zika virus is the most concentrated: any disease spread by mosquitoes is most likely to occur most in warmer areas, a reality that has some looking beyond the number of affected areas today to where it has the potential to spread in the coming years. Last year saw the highest average global temperature of any year in recorded history. Many years of comparable heat levels have taken place in the last two decades.4 Regions around the world are experiencing longer summers and shorter winters. These conditions threaten to extend the annual time period in which mosquitoes can survive, or even bring mosquitoes to areas that don’t typically see them5. The more people come to live in mosquito-friendly areas, the greater the market for vaccines for mosquito-borne illnesses becomes.
Zika virus is not SARS, and it’s not Swine Flu. Aside from its climate-driven potential to spread, the severe birth defects it causes enable it to extend its impact for a generation. Some in the research industry do, however, seem to believe the virus will ultimately follow the historical precedent of those other diseases and prove anti-climactic. As researchers move forward with the vaccines currently in Phase I, these diverse forecasts remind us that, in clinical research, there truly are no guarantees.
1 Branswell, Helen; The race for a Zika vaccine is intense. But it may be missing the most important players; STAT News; 8 August 2016
2 Grills, Ardath; Morrison, Stephanie; Nelson, Bradley; Miniota, Jennifer; Watts, Alexander; Cetron, Martin S.; Projected Zika Virus Importation And Subsequent Ongoing Transmission after Travel to the 2016 Olympic and Paralympic Games — Country-Specific Assessment, July 2016; MMRW Morb Mortal Wkly Rep; 22 July 2016
3 Chang, Daniel; Two new local Zika cases found in Miami; Miami Herald; 15 August 2016
4 National Centers for Environmental Information; https://www.ncdc.noaa.gov/sotc/global/201513
5 Mercer, Greg; The Link Between Zika and Climate Change; The Atlantic; 24 February 2016