Ask the Expert

Why is there a EEE vaccine for horses but not for humans?

Cummings School Professor Sam Telford, an expert on infections spread by mosquitoes and ticks, explains
Two strollers with mosquito netting over them. An expert on infections spread by mosquitos and ticks explains why there is no human vaccine to EEE.
With no human vaccine for EEE, preventive measures are best. Photo: Depositphotos
September 13, 2019

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Actually, there is a human vaccine for eastern equine encephalitis (EEE), but it has never been approved for public use.

The U.S. Army Medical Research Institute of Infectious Diseases—the military medical research institute at Fort Detrick in Maryland—developed a human EEE vaccine in the mid-1980s. That vaccine has been under clinical trial ever since. The human vaccine is only available to those enrolled in the clinical trial, which is both very selective and—for non-active duty personnel—very expensive. Made from the inactivated whole virus, the human vaccine is safe and effective, just like the widely available veterinary vaccines. 

However, like so many experimental vaccines, the human EEE vaccine will never be brought to market for use by the general public. Due to the way biologics are approved for use and marketing by the U.S. Food and Drug Administration, it is too expensive—costing $150 million or more—to undertake the required clinical trials to provide FDA with the supporting data that they need to evaluate the potential product.

Pharmaceutical companies will not devote this time and money unless there is a very good likelihood of recovering their investment, and they would not recoup this outlay for an illness as rare as EEE, despite its severely dangerous nature. And there is no other way to deploy a new vaccine product—it must be approved by the FDA. 

Personally, I think we need another approval pathway that would allow public-health use of experimental vaccines. I have been exploring this given my experience with research and development of the first human Lyme disease vaccine, which was taken off the market by the manufacturer due to poor sales.

One mechanism might be like the groundbreaking Right to Try Act. Clearly, there is a huge difference between allowing terminally ill patients access to experimental drugs and routinely vaccinating to prevent a rare disease, but the door has been opened to thinking outside the box. I’d argue that we need to look at whether such a mechanism might work for new vaccines—and how that could be implemented safely.

Editor’s Note: The opinions of Tufts experts do not necessarily reflect the views of the university.