The hantavirus outbreak on the MV Hondius cruise ship brings a new focus to efforts to develop a vaccine to prevent the virus.
Experts say hantavirus vaccine efforts have repeatedly stalled, in part because outbreaks tend to occur sporadically and disproportionately affect poorer countries where there is less incentive for drugmakers to invest.
“Our funding agencies don’t put a lot of money into this, because it’s likely not to cause the next epidemic or pandemic,” said Sabra Klein, a professor in the molecular microbiology and immunology department at the Johns Hopkins Bloomberg School of Public Health. “But these are hemorrhagic fever viruses, so when they occur, they’re scary, and they do wreak havoc.”
The founders of EnsiliTech, a U.K.-based biotech company, began work on the vaccine 15 years ago.
“We looked at hantavirus and saw it was pretty neglected,” said Matt Slade, a company co-founder and its chief of staff. “There wasn’t really any work in the sector.”
EnsiliTech’ vaccine relies on messenger RNA technology, the same platform used to develop the Covid shots.
The vaccine targets a hantavirus strain known as hantaan virus, which is primarily found in East Asia and can cause internal bleeding and kidney damage, technically referred to as hemorrhagic fever with renal syndrome.
Slade said part of the reason the development process has taken so long is that scientists have been working to make sure the vaccine could be transported at room temperature. The Pfizer and Moderna Covid vaccines had to be transported at very cold temperatures, a requirement that complicated the global rollout of the shots.
EnsiliTech developed a method called “ensilication,” which encases the mRNA in a protective silica cage.
Slade said the vaccine hasn’t yet entered human testing, estimating it could take three to four more years before early-stage clinical trials. The company has successfully done trials in rodents, which are the source of transmission to humans. He didn’t rule out developing another vaccine that targets the Andes strain, the strain responsible for the cruise ship outbreak.
Without the kind of support seen with Operation Warp Speed — the U.S. initiative during President Donald Trump’s first term that fast-tracked the Covid vaccines — it is likely to take five more years to complete Phase 2 and 3 trials. Slade said he is aware of a couple of other hantavirus vaccines that are also in the preclinical stage but none that have reached human trials.
“As was the case with Covid, that can be shortened quite significantly because you get emergency access and get emergency approval,” Slade said. “But if everything kind of stays as with a typical vaccine development, that’s what we would expect to see.”
Even with recently renewed interest amid the hantavirus cruise ship outbreak, “there has to be a strong commercial case for these vaccines,” he said.
“Unfortunately, hantaviruses tend to be endemic in parts of the world that don’t really have that financial backing, so I think there’s just been a lack of interest,” Slade said.
Dr. Ofer Levy, director of the Precision Vaccines Program at Boston Children’s Hospital, said China and South Korea have vaccines, but they have been reported as having mixed results and aren’t available outside those countries.
Americans’ exposure to hantavirus goes as far back as World War II, Levy said, when U.S. soldiers were deployed to Central Europe. Because of that, he said, the U.S. military has previously expressed interest in investing in developing a hantavirus vaccine.
However, outbreaks of the virus have been rare on a global scale, so funding has been an issue.
“There has been no ‘Warp Speed’ for hantavirus,” he said.
